GH-1192 - Migrate code base to jSpecify for nullness verification.

.github/workflows/build.yaml

@@ -31,4 +31,4 @@ jobs:
         ARTIFACTORY_USERNAME: ${{ secrets.ARTIFACTORY_USERNAME }}
         ARTIFACTORY_PASSWORD: ${{ secrets.ARTIFACTORY_PASSWORD }}
         DEVELOCITY_ACCESS_KEY: ${{ secrets.GRADLE_ENTERPRISE_SECRET_ACCESS_KEY }}
-      run: ./mvnw -B clean deploy -Pci,artifactory
+      run: ./mvnw -B clean deploy -Pci,artifactory,nullaway

.mvn/jvm.config

@@ -0,0 +1,10 @@
+--add-exports jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED
+--add-exports jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED
+--add-exports jdk.compiler/com.sun.tools.javac.main=ALL-UNNAMED
+--add-exports jdk.compiler/com.sun.tools.javac.model=ALL-UNNAMED
+--add-exports jdk.compiler/com.sun.tools.javac.parser=ALL-UNNAMED
+--add-exports jdk.compiler/com.sun.tools.javac.processing=ALL-UNNAMED
+--add-exports jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED
+--add-exports jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED
+--add-opens jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED
+--add-opens jdk.compiler/com.sun.tools.javac.comp=ALL-UNNAMED

pom.xml

@@ -37,10 +37,12 @@
 
 		<archunit.version>1.4.0</archunit.version>
 		<artifactory-maven-plugin.version>3.6.2</artifactory-maven-plugin.version>
+		<errorprone.version>2.36.0</errorprone.version>
 		<flapdoodle-mongodb.version>4.16.1</flapdoodle-mongodb.version>
 		<jgit.version>7.0.0.202409031743-r</jgit.version>
 		<jgrapht.version>1.5.2</jgrapht.version>
 		<jmolecules-bom.version>2023.3.1</jmolecules-bom.version>
+		<nullaway.version>0.12.7</nullaway.version>
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
 		<spring-boot.version>4.0.0-SNAPSHOT</spring-boot.version>
@@ -431,6 +433,54 @@ limitations under the License.
 			</build>
 		</profile>
 
+		<profile>
+			<id>nullaway</id>
+			<build>
+				<plugins>
+					<plugin>
+						<groupId>org.apache.maven.plugins</groupId>
+						<artifactId>maven-compiler-plugin</artifactId>
+						<configuration>
+							<showWarnings>true</showWarnings>
+							
+						</configuration>
+						<executions>
+							<execution>
+								<id>default-compile</id>
+								<phase>none</phase>
+							</execution>
+							<execution>
+								<id>java-compile</id>
+								<phase>compile</phase>
+								<goals>
+									<goal>compile</goal>
+								</goals>
+								<configuration>
+									<annotationProcessorPaths>
+										<path>
+											<groupId>com.google.errorprone</groupId>
+											<artifactId>error_prone_core</artifactId>
+											<version>${errorprone.version}</version>
+										</path>
+										<path>
+											<groupId>com.uber.nullaway</groupId>
+											<artifactId>nullaway</artifactId>
+											<version>${nullaway.version}</version>
+										</path>
+									</annotationProcessorPaths>
+									<compilerArgs>
+										<arg>-XDcompilePolicy=simple</arg>
+										<arg>--should-stop=ifError=FLOW</arg>
+										<arg>-Xplugin:ErrorProne -XepDisableAllChecks -Xep:NullAway:ERROR -XepOpt:NullAway:OnlyNullMarked=true -XepOpt:NullAway:CustomContractAnnotations=org.springframework.lang.Contract</arg>
+									</compilerArgs>
+								</configuration>
+							</execution>
+						</executions>
+					</plugin>
+				</plugins>
+			</build>
+		</profile>
+
 	</profiles>
 
 	<dependencies>

spring-modulith-actuator/pom.xml

@@ -16,6 +16,11 @@
 
 	<dependencies>
 
+    <dependency>
+      <groupId>org.jspecify</groupId>
+      <artifactId>jspecify</artifactId>
+    </dependency>
+
 		<dependency>
 			<groupId>org.springframework.modulith</groupId>
 			<artifactId>spring-modulith-runtime</artifactId>

spring-modulith-actuator/src/main/java/org/springframework/modulith/actuator/autoconfigure/package-info.java

@@ -1,5 +1,5 @@
 /**
  * Autoconfiguration for Spring Modulith actuators.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.modulith.actuator.autoconfigure;

spring-modulith-actuator/src/main/java/org/springframework/modulith/actuator/package-info.java

@@ -1,5 +1,5 @@
 /**
  * Spring Boot actuator support for Spring Modulith.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.modulith.actuator;

spring-modulith-api/pom.xml

@@ -17,6 +17,11 @@
 
 	<dependencies>
 
+		<dependency>
+			<groupId>org.jspecify</groupId>
+			<artifactId>jspecify</artifactId>
+		</dependency>
+
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-autoconfigure</artifactId>

spring-modulith-api/src/main/java/org/springframework/modulith/package-info.java

@@ -1,5 +1,5 @@
 /**
  * Core abstractions of Spring Modulith. To be referred to in user applications.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.modulith;

spring-modulith-apt/pom.xml

@@ -21,6 +21,10 @@
 			<artifactId>aptk-tools</artifactId>
 			<version>0.29.0</version>
 		</dependency>
+    <dependency>
+      <groupId>org.jspecify</groupId>
+      <artifactId>jspecify</artifactId>
+    </dependency>
 
 		<dependency>
 			<groupId>org.springframework.boot</groupId>

spring-modulith-apt/src/main/java/org/springframework/modulith/apt/SpringModulithProcessor.java

@@ -19,6 +19,7 @@ import io.toolisticon.aptk.tools.ElementUtils;
 import io.toolisticon.aptk.tools.wrapper.ElementWrapper;
 import io.toolisticon.aptk.tools.wrapper.ExecutableElementWrapper;
 import io.toolisticon.aptk.tools.wrapper.TypeElementWrapper;
+import org.jspecify.annotations.Nullable;
 
 import java.io.File;
 import java.io.FileWriter;
@@ -50,7 +51,6 @@ import javax.tools.Diagnostic.Kind;
 import javax.tools.StandardLocation;
 
 import org.springframework.boot.json.JsonWriter;
-import org.springframework.lang.Nullable;
 import org.springframework.modulith.docs.metadata.MethodMetadata;
 import org.springframework.modulith.docs.metadata.TypeMetadata;
 import org.springframework.modulith.docs.util.BuildSystemUtils;

spring-modulith-core/pom.xml

@@ -17,6 +17,11 @@
 
 	<dependencies>
 
+		<dependency>
+			<groupId>org.jspecify</groupId>
+			<artifactId>jspecify</artifactId>
+		</dependency>
+
 		<dependency>
 			<groupId>org.springframework.modulith</groupId>
 			<artifactId>spring-modulith-api</artifactId>

spring-modulith-core/src/main/java/org/springframework/modulith/core/ApplicationModule.java

@@ -36,7 +36,7 @@ import java.util.function.Supplier;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 import org.springframework.modulith.core.Types.JMoleculesTypes;
 import org.springframework.modulith.core.Types.JavaTypes;
 import org.springframework.modulith.core.Types.SpringTypes;
@@ -427,7 +427,7 @@ public class ApplicationModule implements Comparable<ApplicationModule> {
 
 		var candidatePackageName = PackageName.ofType(candidate);
 
-		return (candidatePackageName.isEmpty() || basePackage.getPackageName().contains(candidatePackageName))
+		return (PackageName.isDefault(candidatePackageName) || basePackage.getPackageName().contains(candidatePackageName))
 				&& getType(candidate).isPresent();
 	}
 

spring-modulith-core/src/main/java/org/springframework/modulith/core/ApplicationModuleDependencies.java

@@ -21,6 +21,7 @@ import java.util.List;
 import java.util.function.Function;
 import java.util.stream.Stream;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -172,7 +173,7 @@ public class ApplicationModuleDependencies {
 	 * @param name must not be {@literal null} or empty.
 	 * @return will never be {@literal null}.
 	 */
-	public ApplicationModule getModuleByType(String name) {
+	public @Nullable ApplicationModule getModuleByType(String name) {
 
 		Assert.hasText(name, "Name must not be null or empty!");
 

spring-modulith-core/src/main/java/org/springframework/modulith/core/ApplicationModuleSource.java

@@ -21,6 +21,7 @@ import java.util.Optional;
 import java.util.function.Function;
 import java.util.stream.Stream;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.modulith.ApplicationModule;
 import org.springframework.modulith.core.Types.JMoleculesTypes;
 import org.springframework.util.Assert;
@@ -240,7 +241,7 @@ public class ApplicationModuleSource {
 		 * @param delegates must not be {@literal null}.
 		 * @return will never be {@literal null}.
 		 */
-		private static ApplicationModuleSourceMetadata delegating(ApplicationModuleSourceMetadata... delegates) {
+		private static ApplicationModuleSourceMetadata delegating(@Nullable ApplicationModuleSourceMetadata... delegates) {
 
 			return new ApplicationModuleSourceMetadata() {
 

spring-modulith-core/src/main/java/org/springframework/modulith/core/ApplicationModuleSourceFactory.java

@@ -20,7 +20,7 @@ import java.util.List;
 import java.util.function.Function;
 import java.util.stream.Stream;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * SPI to allow build units contribute additional {@link ApplicationModuleSource}s in the form of either declaring them

spring-modulith-core/src/main/java/org/springframework/modulith/core/ApplicationModules.java

@@ -32,9 +32,9 @@ import java.util.stream.Collectors;
 import java.util.stream.Stream;
 import java.util.stream.StreamSupport;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.aot.generate.Generated;
 import org.springframework.core.annotation.AnnotationAwareOrderComparator;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.function.SingletonSupplier;
@@ -61,7 +61,7 @@ public class ApplicationModules implements Iterable<ApplicationModule> {
 	private static final Map<CacheKey, ApplicationModules> CACHE = new ConcurrentHashMap<>();
 
 	private static final ImportOption IMPORT_OPTION = new ImportOption.DoNotIncludeTests();
-	private static final DescribedPredicate<CanBeAnnotated> IS_GENERATED;
+	private static final @Nullable DescribedPredicate<CanBeAnnotated> IS_GENERATED;
 	private static final DescribedPredicate<HasName> IS_SPRING_CGLIB_PROXY = nameContaining("$$SpringCGLIB$$");
 
 	static {
@@ -624,9 +624,9 @@ public class ApplicationModules implements Iterable<ApplicationModule> {
 	 * {@literal null} or its type does not reside in any module.
 	 *
 	 * @param object can be {@literal null}.
-	 * @return
+	 * @return can be {@literal null}.
 	 */
-	private Integer getModuleIndexFor(@Nullable Object object) {
+	private @Nullable Integer getModuleIndexFor(@Nullable Object object) {
 
 		return Optional.ofNullable(object)
 				.map(it -> Class.class.isInstance(it) ? Class.class.cast(it) : it.getClass())
@@ -778,7 +778,7 @@ public class ApplicationModules implements Iterable<ApplicationModule> {
 		 * @see java.lang.Object#equals(java.lang.Object)
 		 */
 		@Override
-		public boolean equals(Object obj) {
+		public boolean equals(@Nullable Object obj) {
 
 			if (obj == this) {
 				return true;

spring-modulith-core/src/main/java/org/springframework/modulith/core/ArchitecturallyEvidentType.java

@@ -20,6 +20,7 @@ import static org.springframework.modulith.core.Types.JavaXTypes.*;
 
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashSet;
 import java.util.List;
@@ -676,7 +677,9 @@ public abstract class ArchitecturallyEvidentType {
 			var attributes = AnnotatedElementUtils.getMergedAnnotationAttributes(method.reflect(),
 					SpringTypes.AT_EVENT_LISTENER, false, false);
 
-			return List.of(attributes.getClassArray("classes"));
+			return attributes == null
+					? Collections.emptyList()
+					: List.of(attributes.getClassArray("classes"));
 		}
 
 		/*

spring-modulith-core/src/main/java/org/springframework/modulith/core/Classes.java

@@ -29,7 +29,7 @@ import java.util.stream.Collectors;
 import java.util.stream.Stream;
 import java.util.stream.StreamSupport;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 

spring-modulith-core/src/main/java/org/springframework/modulith/core/FormattableType.java

@@ -22,7 +22,7 @@ import java.util.stream.Collectors;
 import java.util.stream.Stream;
 import java.util.stream.StreamSupport;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.StringUtils;

spring-modulith-core/src/main/java/org/springframework/modulith/core/ModulithMetadata.java

@@ -75,7 +75,12 @@ public interface ModulithMetadata {
 			return SpringBootModulithMetadata.of(javaPackage);
 		}
 
-		var className = candidates.iterator().next().getBeanClassName();
+		var definition = candidates.iterator().next();
+		var className = definition.getBeanClassName();
+
+		if (className == null) {
+			throw new IllegalStateException("No bean class name found on BeanDefinition %s!".formatted(definition));
+		}
 
 		return of(ClassUtils.resolveClassName(className, ModulithMetadata.class.getClassLoader()));
 	}

spring-modulith-core/src/main/java/org/springframework/modulith/core/NamedInterfaces.java

@@ -298,6 +298,10 @@ public class NamedInterfaces implements Iterable<NamedInterface> {
 					var annotation = AnnotatedElementUtils.getMergedAnnotation(it.reflect(),
 							org.springframework.modulith.NamedInterface.class);
 
+					if (annotation == null) {
+						throw new IllegalStateException("No @NamedInterface annotation found!");
+					}
+
 					NamedInterface.getDefaultedNames(annotation, it.getPackageName())
 							.forEach(name -> mappings.add(name, it));
 				});

spring-modulith-core/src/main/java/org/springframework/modulith/core/PackageName.java

@@ -18,10 +18,11 @@ package org.springframework.modulith.core;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Objects;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 
@@ -34,6 +35,8 @@ import org.springframework.util.ClassUtils;
  */
 public class PackageName implements Comparable<PackageName> {
 
+	public static final String DEFAULT = "<<default>>";
+
 	private static final Map<String, PackageName> PACKAGE_NAMES = new HashMap<>();
 
 	private final String name;
@@ -77,6 +80,20 @@ public class PackageName implements Comparable<PackageName> {
 		return PackageName.of(ClassUtils.getPackageName(fullyQualifiedName));
 	}
 
+	/**
+	 * Creates a new {@link PackageName} for the given fully-qualified type name.
+	 *
+	 * @param fullyQualifiedName must not be {@literal null} or empty.
+	 * @return will never be {@literal null}.
+	 * @since 2.0
+	 */
+	public static PackageName ofType(Class<?> type) {
+
+		Assert.notNull(type, "Type must not be null!");
+
+		return PackageName.of(ClassUtils.getPackageName(type));
+	}
+
 	/**
 	 * Returns the {@link PackageName} with the given name.
 	 *
@@ -88,7 +105,9 @@ public class PackageName implements Comparable<PackageName> {
 
 		Assert.notNull(name, "Name must not be null!");
 
-		return PACKAGE_NAMES.computeIfAbsent(name, PackageName::new);
+		var defaulted = name.isBlank() ? DEFAULT : name;
+
+		return PACKAGE_NAMES.computeIfAbsent(defaulted, PackageName::new);
 	}
 
 	/**
@@ -107,6 +126,16 @@ public class PackageName implements Comparable<PackageName> {
 		return PACKAGE_NAMES.computeIfAbsent(name, it -> new PackageName(name, segments));
 	}
 
+	/**
+	 * Returns whether the given {@link PackageName} is the default package name (logically an empty string).
+	 *
+	 * @param name must not be {@literal null}.
+	 * @since 2.0
+	 */
+	static boolean isDefault(PackageName name) {
+		return name.hasName(DEFAULT);
+	}
+
 	/**
 	 * Returns the length of the package name.
 	 *
@@ -281,7 +310,9 @@ public class PackageName implements Comparable<PackageName> {
 			return Stream.of(reference);
 		}
 
-		return Stream.concat(expandUntil(reference.getParent()), Stream.of(reference));
+		var parent = Objects.requireNonNull(reference.getParent());
+
+		return Stream.concat(expandUntil(parent), Stream.of(reference));
 	}
 
 	/**
@@ -318,7 +349,7 @@ public class PackageName implements Comparable<PackageName> {
 	 * @see java.lang.Object#equals(java.lang.Object)
 	 */
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 
 		if (obj == this) {
 			return true;

spring-modulith-core/src/main/java/org/springframework/modulith/core/SpringBootModulithMetadata.java

@@ -21,8 +21,8 @@ import java.util.List;
 import java.util.Optional;
 import java.util.stream.Stream;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.core.annotation.AnnotatedElementUtils;
-import org.springframework.lang.NonNull;
 import org.springframework.modulith.core.Types.SpringTypes;
 import org.springframework.util.Assert;
 
@@ -34,20 +34,21 @@ import org.springframework.util.Assert;
  */
 class SpringBootModulithMetadata implements ModulithMetadata {
 
-	private static final Class<? extends Annotation> AT_SPRING_BOOT_APPLICATION = Types
+	private static final @Nullable Class<? extends Annotation> AT_SPRING_BOOT_APPLICATION = Types
 			.loadIfPresent(SpringTypes.AT_SPRING_BOOT_APPLICATION);
 
-	private final @NonNull Object source;
-	private final String systemName, basePackage;
+	private final Object source;
+	private final String basePackage;
+	private final @Nullable String systemName;
 
 	/**
 	 * Creates a new {@link SpringBootModulithMetadata} for the given source.
 	 *
 	 * @param source must not be {@literal null}.
-	 * @param systemName can be {@literal null}.
 	 * @param basePackage must not be {@literal null}.
+	 * @param systemName can be {@literal null}.
 	 */
-	private SpringBootModulithMetadata(Object source, String systemName, String basePackage) {
+	private SpringBootModulithMetadata(Object source, String basePackage, @Nullable String systemName) {
 
 		Assert.notNull(source, "Source must not be null!");
 		Assert.notNull(basePackage, "Base package must not be null!");
@@ -71,7 +72,7 @@ class SpringBootModulithMetadata implements ModulithMetadata {
 
 		return Optional.ofNullable(AT_SPRING_BOOT_APPLICATION) //
 				.filter(it -> AnnotatedElementUtils.hasAnnotation(annotated, it)) //
-				.map(__ -> new SpringBootModulithMetadata(annotated, annotated.getSimpleName(), annotated.getPackageName()));
+				.map(__ -> new SpringBootModulithMetadata(annotated, annotated.getPackageName(), annotated.getSimpleName()));
 	}
 
 	/**
@@ -84,7 +85,7 @@ class SpringBootModulithMetadata implements ModulithMetadata {
 
 		Assert.hasText(javaPackage, "Package name must not be null or empty!");
 
-		return new SpringBootModulithMetadata(javaPackage, null, javaPackage);
+		return new SpringBootModulithMetadata(javaPackage, javaPackage, null);
 	}
 
 	/*

spring-modulith-core/src/main/java/org/springframework/modulith/core/Types.java

@@ -26,7 +26,7 @@ import java.util.function.Predicate;
 import org.jmolecules.archunit.JMoleculesArchitectureRules;
 import org.jmolecules.archunit.JMoleculesDddRules;
 import org.jmolecules.ddd.annotation.Module;
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 import org.springframework.modulith.PackageInfo;
 import org.springframework.modulith.core.ApplicationModuleSource.ApplicationModuleSourceMetadata;
 import org.springframework.util.Assert;
@@ -82,7 +82,7 @@ public class Types {
 		static final String AT_DOMAIN_EVENT = BASE_PACKAGE + ".event.annotation.DomainEvent";
 		static final String DOMAIN_EVENT = BASE_PACKAGE + ".event.types.DomainEvent";
 
-		private static Collection<ArchRule> RULES;
+		private static @Nullable Collection<ArchRule> RULES;
 
 		/**
 		 * Returns whether jMolecules is generally present.
@@ -123,34 +123,38 @@ public class Types {
 		 */
 		public static Collection<ArchRule> getRules() {
 
-			if (RULES == null) {
+			var rules = RULES;
+
+			if (rules == null) {
 
 				var classLoader = JMoleculesTypes.class.getClassLoader();
-				RULES = new ArrayList<ArchRule>();
+				rules = new ArrayList<ArchRule>();
 
 				if (ClassUtils.isPresent(DDD_RULES, classLoader)) {
-					RULES.add(JMoleculesDddRules.all());
+					rules.add(JMoleculesDddRules.all());
 				}
 
 				if (!ClassUtils.isPresent(ARCHITECTURE_RULES, classLoader)) {
-					return RULES;
+					return rules;
 				}
 
 				if (ClassUtils.isPresent(HEXAGONAL, classLoader)) {
-					RULES.add(JMoleculesArchitectureRules.ensureHexagonal());
+					rules.add(JMoleculesArchitectureRules.ensureHexagonal());
 				}
 
 				if (ClassUtils.isPresent(LAYERED, classLoader)) {
-					RULES.add(JMoleculesArchitectureRules.ensureLayering());
+					rules.add(JMoleculesArchitectureRules.ensureLayering());
 				}
 
 				if (ClassUtils.isPresent(ONION, classLoader)) {
-					RULES.add(JMoleculesArchitectureRules.ensureOnionClassical());
-					RULES.add(JMoleculesArchitectureRules.ensureOnionSimple());
+					rules.add(JMoleculesArchitectureRules.ensureOnionClassical());
+					rules.add(JMoleculesArchitectureRules.ensureOnionSimple());
 				}
+
+				RULES = rules;
 			}
 
-			return RULES;
+			return rules;
 		}
 	}
 

spring-modulith-core/src/main/java/org/springframework/modulith/core/config/package-info.java

@@ -1,5 +1,5 @@
 /**
  * Core configuration abstractions of Spring Modulith.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.modulith.core.config;

spring-modulith-core/src/main/java/org/springframework/modulith/core/package-info.java

@@ -1,5 +1,5 @@
 /**
  * Core, internal abstractions of Spring Modulith.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.modulith.core;

spring-modulith-core/src/test/java/org/springframework/modulith/core/ApplicationModulesUnitTests.java

@@ -80,4 +80,12 @@ class ApplicationModulesUnitTests {
 						it -> assertThat(it).contains("Invalid", "'invalid'", "'ni.nested.b.first'"),
 						it -> assertThat(it).contains("Invalid", "'ni'", "'ni.nested.b.first'"));
 	}
+
+	@Test // GH-1192
+	void findsTypeBySimpleName() {
+
+		assertThat(modules.getModuleByName("ni")).hasValueSatisfying(it -> {
+			assertThat(it.contains("RootType")).isTrue();
+		});
+	}
 }

spring-modulith-docs/pom.xml

@@ -17,6 +17,11 @@
 
 	<dependencies>
 
+		<dependency>
+			<groupId>org.jspecify</groupId>
+			<artifactId>jspecify</artifactId>
+		</dependency>
+
 		<dependency>
 			<groupId>${project.groupId}</groupId>
 			<artifactId>spring-modulith-core</artifactId>

spring-modulith-docs/src/main/java/org/springframework/modulith/docs/Asciidoctor.java

@@ -25,9 +25,9 @@ import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 import java.util.stream.Stream;
 
+import org.jspecify.annotations.Nullable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-import org.springframework.lang.Nullable;
 import org.springframework.modulith.core.ApplicationModule;
 import org.springframework.modulith.core.ApplicationModuleDependency;
 import org.springframework.modulith.core.ApplicationModules;

spring-modulith-docs/src/main/java/org/springframework/modulith/docs/ConfigurationProperties.java

@@ -23,9 +23,9 @@ import java.util.List;
 import java.util.Map;
 import java.util.stream.Stream;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
-import org.springframework.lang.Nullable;
 import org.springframework.modulith.core.ApplicationModule;
 import org.springframework.modulith.docs.ConfigurationProperties.ConfigurationProperty;
 import org.springframework.util.Assert;
@@ -124,7 +124,6 @@ class ConfigurationProperties implements Iterable<ConfigurationProperty> {
 	static record ConfigurationProperty(String name, @Nullable String description, String type, String sourceType,
 			@Nullable String defaultValue) {
 
-		@SuppressWarnings("null")
 		static Stream<ConfigurationProperty> of(Map<String, Object> source) {
 
 			String sourceType = getAsString(source, "sourceType");
@@ -133,9 +132,9 @@ class ConfigurationProperties implements Iterable<ConfigurationProperty> {
 				return Stream.empty();
 			}
 
-			ConfigurationProperty property = new ConfigurationProperty(getAsString(source, "name"),
+			ConfigurationProperty property = new ConfigurationProperty(getRequiredAsString(source, "name"),
 					getAsString(source, "description"),
-					getAsString(source, "type"),
+					getRequiredAsString(source, "type"),
 					sourceType,
 					getAsString(source, "defaultValue"));
 
@@ -146,6 +145,15 @@ class ConfigurationProperties implements Iterable<ConfigurationProperty> {
 			return StringUtils.hasText(sourceType);
 		}
 
+		private static String getRequiredAsString(Map<String, Object> source, String key) {
+
+			var value = getAsString(source, key);
+
+			Assert.notNull(value, "No value found for key %s in %s!".formatted(key, source));
+
+			return value;
+		}
+
 		private static @Nullable String getAsString(Map<String, Object> source, String key) {
 
 			Object value = source.get(key);

spring-modulith-docs/src/main/java/org/springframework/modulith/docs/Documenter.java

@@ -36,7 +36,8 @@ import java.util.function.Supplier;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+import org.springframework.lang.Contract;
 import org.springframework.modulith.core.ApplicationModule;
 import org.springframework.modulith.core.ApplicationModules;
 import org.springframework.modulith.core.DependencyDepth;
@@ -98,7 +99,7 @@ public class Documenter {
 
 	private boolean cleared;
 
-	private Map<ApplicationModule, Component> components;
+	private @Nullable Map<ApplicationModule, Component> components;
 
 	/**
 	 * Creates a new {@link Documenter} for the {@link ApplicationModules} created for the given modulith type in the
@@ -223,6 +224,7 @@ public class Documenter {
 	 * @return the current instance, will never be {@literal null}.
 	 * @since 1.2.2
 	 */
+	@Contract("_, _ -> this")
 	public Documenter writeAggregatingDocument(DiagramOptions diagramOptions, CanvasOptions canvasOptions) {
 
 		Assert.notNull(diagramOptions, "DiagramOptions must not be null!");
@@ -485,18 +487,19 @@ public class Documenter {
 				.forEach(it -> it.addTags(DependencyType.USES_COMPONENT.toString()));
 	}
 
+	@SuppressWarnings("null")
 	private Map<ApplicationModule, Component> getComponents(DiagramOptions options) {
 
-		if (components == null) {
+		if (this.components == null) {
 
 			this.components = modules.stream() //
 					.collect(Collectors.toMap(Function.identity(),
 							it -> container.addComponent(options.defaultDisplayName.apply(it), "", "Module")));
 
-			this.components.forEach((key, value) -> addDependencies(key, value, options));
+			components.forEach((key, value) -> addDependencies(key, value, options));
 		}
 
-		return components;
+		return this.components;
 	}
 
 	private void addComponentsToView(ApplicationModule module, ComponentView view, DiagramOptions options) {
@@ -643,6 +646,11 @@ public class Documenter {
 			Styles styles) {
 
 		var component = components.get(module);
+
+		if (component == null) {
+			throw new IllegalStateException("Couldn't find component for module %s!".formatted(module));
+		}
+
 		var selector = options.colorSelector;
 
 		// Apply custom color if configured
@@ -1061,6 +1069,7 @@ public class Documenter {
 			return new CanvasOptions(groupers, apiBase, targetFileName, hideInternals, hideEmptyLines);
 		}
 
+		@Nullable
 		String getApiBase() {
 			return apiBase;
 		}
@@ -1083,7 +1092,10 @@ public class Documenter {
 
 			// Wipe entries without any beans
 			new HashSet<>(result.keySet()).forEach(key -> {
-				if (result.get(key).isEmpty()) {
+
+				var value = result.get(key);
+
+				if (value != null && value.isEmpty()) {
 					result.remove(key);
 				}
 			});
@@ -1161,10 +1173,10 @@ public class Documenter {
 			 *
 			 * @param name must not be {@literal null} or empty.
 			 * @param predicate must not be {@literal null}.
-			 * @param description must not be {@literal null} or empty.
+			 * @param description can be {@literal null}.
 			 * @return will never be {@literal null}.
 			 */
-			public static Grouping of(String name, Predicate<SpringBean> predicate, String description) {
+			public static Grouping of(String name, Predicate<SpringBean> predicate, @Nullable String description) {
 				return new Grouping(name, predicate, description);
 			}
 

spring-modulith-docs/src/main/java/org/springframework/modulith/docs/SpringModulithDocumentationSource.java

@@ -23,9 +23,9 @@ import java.util.List;
 import java.util.Map;
 import java.util.Optional;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.boot.json.BasicJsonParser;
 import org.springframework.core.io.Resource;
-import org.springframework.lang.Nullable;
 import org.springframework.modulith.docs.metadata.MethodMetadata;
 import org.springframework.modulith.docs.metadata.TypeMetadata;
 import org.springframework.modulith.docs.util.BuildSystemUtils;
@@ -134,28 +134,39 @@ class SpringModulithDocumentationSource implements DocumentationSource {
 	@SuppressWarnings("unchecked")
 	private static TypeMetadata typeMetadata(Map<String, Object> source) {
 
-		var methods = source.containsKey("methods")
-				? ((List<Map<String, Object>>) source.get("methods")).stream()
-						.map(SpringModulithDocumentationSource::methodMetadata)
-						.toList()
+		var sourceMethods = (List<Map<String, Object>>) source.get("methods");
+
+		var methods = sourceMethods != null
+				? sourceMethods.stream().map(SpringModulithDocumentationSource::methodMetadata).toList()
 				: Collections.<MethodMetadata> emptyList();
 
-		return new TypeMetadata(
-				source.get("name").toString(),
-				getString(source, "comment"),
-				methods);
+		var name = source.get("name");
+
+		if (name == null) {
+			throw new IllegalArgumentException("Source map does not contain a name entry! %s".formatted(source));
+		}
+
+		return new TypeMetadata(name.toString(), getString(source, "comment"), methods);
 	}
 
 	private static MethodMetadata methodMetadata(Map<String, Object> source) {
 
-		return new MethodMetadata(
-				source.get("name").toString(),
-				source.get("signature").toString(),
-				getString(source, "comment"));
+		var name = source.get("name");
+
+		if (name == null) {
+			throw new IllegalArgumentException("No name found in source map! %s".formatted(source));
+		}
+
+		var signature = source.get("signature");
+
+		if (signature == null) {
+			throw new IllegalArgumentException("No signature found in source map! %s".formatted(source));
+		}
+
+		return new MethodMetadata(name.toString(), signature.toString(), getString(source, "comment"));
 	}
 
-	@Nullable
-	private static String getString(Map<String, Object> source, String key) {
+	private static @Nullable String getString(Map<String, Object> source, String key) {
 
 		Object result = source.get(key);
 

spring-modulith-docs/src/main/java/org/springframework/modulith/docs/metadata/MethodMetadata.java

@@ -19,7 +19,7 @@ import java.lang.reflect.Method;
 import java.util.Arrays;
 import java.util.stream.Collectors;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 import org.springframework.util.Assert;
 
 /**

spring-modulith-docs/src/main/java/org/springframework/modulith/docs/metadata/TypeMetadata.java

@@ -17,7 +17,7 @@ package org.springframework.modulith.docs.metadata;
 
 import java.util.List;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Metadata about a Java type.

spring-modulith-docs/src/main/java/org/springframework/modulith/docs/package-info.java

@@ -1,5 +1,5 @@
 /**
  * Documentation support for Spring Modulith.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.modulith.docs;

spring-modulith-events/spring-modulith-events-amqp/pom.xml

@@ -17,6 +17,11 @@
 
 	<dependencies>
 
+		<dependency>
+			<groupId>org.jspecify</groupId>
+			<artifactId>jspecify</artifactId>
+		</dependency>
+
 		<dependency>
 			<groupId>org.springframework.modulith</groupId>
 			<artifactId>spring-modulith-api</artifactId>

spring-modulith-events/spring-modulith-events-amqp/src/main/java/org/springframework/modulith/events/amqp/package-info.java

@@ -1,5 +1,5 @@
 /**
  * AMQP event externalization support.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.modulith.events.amqp;

spring-modulith-events/spring-modulith-events-api/pom.xml

@@ -17,6 +17,11 @@
 
 	<dependencies>
 
+		<dependency>
+			<groupId>org.jspecify</groupId>
+			<artifactId>jspecify</artifactId>
+		</dependency>
+
 		<dependency>
 			<groupId>org.springframework</groupId>
 			<artifactId>spring-context</artifactId>

spring-modulith-events/spring-modulith-events-api/src/main/java/org/springframework/modulith/events/AnnotationTargetLookup.java

@@ -25,6 +25,7 @@ import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.function.Supplier;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.modulith.events.RoutingTarget.ParsedRoutingTarget;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
@@ -45,7 +46,7 @@ class AnnotationTargetLookup implements Supplier<Optional<ParsedRoutingTarget>>
 
 	private static Map<Class<?>, AnnotationTargetLookup> LOOKUPS = new ConcurrentReferenceHashMap<>(25);
 	private static final String JMOLECULES_EXTERNALIZED = "org.jmolecules.event.annotation.Externalized";
-	private static final Class<? extends Annotation> JMOLECULES_ANNOTATION = loadJMoleculesExternalizedIfPresent();
+	private static final @Nullable Class<? extends Annotation> JMOLECULES_ANNOTATION = loadJMoleculesExternalizedIfPresent();
 
 	private final Class<?> type;
 	private final Supplier<Optional<ParsedRoutingTarget>> lookup;
@@ -159,7 +160,7 @@ class AnnotationTargetLookup implements Supplier<Optional<ParsedRoutingTarget>>
 	}
 
 	@SuppressWarnings("unchecked")
-	private static Class<? extends Annotation> loadJMoleculesExternalizedIfPresent() {
+	private static @Nullable Class<? extends Annotation> loadJMoleculesExternalizedIfPresent() {
 
 		var classLoader = DefaultEventExternalizationConfiguration.class.getClassLoader();
 

spring-modulith-events/spring-modulith-events-api/src/main/java/org/springframework/modulith/events/EventExternalizationConfiguration.java

@@ -28,8 +28,8 @@ import java.util.function.BiPredicate;
 import java.util.function.Function;
 import java.util.function.Predicate;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.core.annotation.AnnotatedElementUtils;
-import org.springframework.lang.Nullable;
 import org.springframework.modulith.events.RoutingTarget.ParsedRoutingTarget;
 import org.springframework.modulith.events.RoutingTarget.RoutingTargetBuilder;
 import org.springframework.util.Assert;
@@ -359,7 +359,16 @@ public interface EventExternalizationConfiguration {
 		}
 
 		private static <T extends Annotation> T findAnnotation(Object event, Class<T> annotationType) {
-			return findMergedAnnotation(event.getClass(), annotationType);
+
+			var type = event.getClass();
+			var result = findMergedAnnotation(type, annotationType);
+
+			if (result == null) {
+				throw new IllegalStateException(
+						"Couldn't find annotation %s on type %s!".formatted(annotationType, type));
+			}
+
+			return result;
 		}
 	}
 

spring-modulith-events/spring-modulith-events-api/src/main/java/org/springframework/modulith/events/EventExternalized.java

@@ -17,9 +17,10 @@ package org.springframework.modulith.events;
 
 import java.util.Objects;
 
+import org.jspecify.annotations.NonNull;
+import org.jspecify.annotations.Nullable;
 import org.springframework.core.ResolvableType;
 import org.springframework.core.ResolvableTypeProvider;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -103,7 +104,7 @@ public class EventExternalized<S, T> implements ResolvableTypeProvider {
 	 *
 	 * @return can be {@literal null}.
 	 */
-	public T getBrokerResult() {
+	public @Nullable T getBrokerResult() {
 		return brokerResult;
 	}
 
@@ -112,7 +113,7 @@ public class EventExternalized<S, T> implements ResolvableTypeProvider {
 	 * @see org.springframework.core.ResolvableTypeProvider#getResolvableType()
 	 */
 	@Override
-	public ResolvableType getResolvableType() {
+	public @NonNull ResolvableType getResolvableType() {
 		return type;
 	}
 

spring-modulith-events/spring-modulith-events-api/src/main/java/org/springframework/modulith/events/RoutingTarget.java

@@ -17,7 +17,7 @@ package org.springframework.modulith.events;
 
 import java.util.Objects;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
@@ -238,14 +238,14 @@ public class RoutingTarget {
 		/**
 		 * @return the target
 		 */
-		public String getTarget() {
+		public @Nullable String getTarget() {
 			return target;
 		}
 
 		/**
 		 * @return the key
 		 */
-		public String getKey() {
+		public @Nullable String getKey() {
 			return key;
 		}
 

spring-modulith-events/spring-modulith-events-api/src/main/java/org/springframework/modulith/events/package-info.java

@@ -1,5 +1,5 @@
 /**
  * API of the event publication registry abstraction.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.modulith.events;

spring-modulith-events/spring-modulith-events-core/pom.xml

@@ -17,6 +17,11 @@
 	</properties>
 
 	<dependencies>
+		
+		<dependency>
+			<groupId>org.jspecify</groupId>
+			<artifactId>jspecify</artifactId>
+		</dependency>
 
 		<dependency>
 			<groupId>org.springframework.modulith</groupId>

spring-modulith-events/spring-modulith-events-core/src/main/java/org/springframework/modulith/events/aot/ApplicationListenerMethodAdapterRuntimeHints.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.modulith.events.aot;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.aot.hint.ExecutableMode;
 import org.springframework.aot.hint.RuntimeHints;
 import org.springframework.aot.hint.RuntimeHintsRegistrar;
@@ -32,7 +33,7 @@ public class ApplicationListenerMethodAdapterRuntimeHints implements RuntimeHint
 	 * @see org.springframework.aot.hint.RuntimeHintsRegistrar#registerHints(org.springframework.aot.hint.RuntimeHints, java.lang.ClassLoader)
 	 */
 	@Override
-	public void registerHints(RuntimeHints hints, ClassLoader classLoader) {
+	public void registerHints(RuntimeHints hints, @Nullable ClassLoader classLoader) {
 
 		var reflection = hints.reflection();
 

spring-modulith-events/spring-modulith-events-core/src/main/java/org/springframework/modulith/events/aot/TransactionalEventListenerAotProcessor.java

@@ -17,6 +17,7 @@ package org.springframework.modulith.events.aot;
 
 import java.util.Arrays;
 
+import org.jspecify.annotations.Nullable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.aot.hint.MemberCategory;
@@ -43,7 +44,7 @@ public class TransactionalEventListenerAotProcessor implements BeanRegistrationA
 	 * @see org.springframework.beans.factory.aot.BeanRegistrationAotProcessor#processAheadOfTime(org.springframework.beans.factory.support.RegisteredBean)
 	 */
 	@Override
-	public BeanRegistrationAotContribution processAheadOfTime(RegisteredBean registeredBean) {
+	public @Nullable BeanRegistrationAotContribution processAheadOfTime(RegisteredBean registeredBean) {
 
 		Class<?> type = registeredBean.getBeanType().resolve(Object.class);
 

spring-modulith-events/spring-modulith-events-core/src/main/java/org/springframework/modulith/events/aot/package-info.java

@@ -1,5 +1,5 @@
 /**
  * AOT support for the Event Publication Registry.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.modulith.events.aot;

spring-modulith-events/spring-modulith-events-core/src/main/java/org/springframework/modulith/events/config/EventPublicationAutoConfiguration.java

@@ -19,6 +19,7 @@ import java.time.Clock;
 import java.time.Duration;
 import java.util.Arrays;
 
+import org.jspecify.annotations.NonNull;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.BeansException;
@@ -37,7 +38,6 @@ import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Import;
 import org.springframework.context.annotation.Role;
 import org.springframework.core.env.Environment;
-import org.springframework.lang.NonNull;
 import org.springframework.modulith.events.config.EventPublicationAutoConfiguration.AsyncEnablingConfiguration;
 import org.springframework.modulith.events.core.DefaultEventPublicationRegistry;
 import org.springframework.modulith.events.core.EventPublicationRegistry;

spring-modulith-events/spring-modulith-events-core/src/main/java/org/springframework/modulith/events/config/package-info.java

@@ -1,5 +1,5 @@
 /**
  * Spring configuration for the Event Publication Registry.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.modulith.events.config;

spring-modulith-events/spring-modulith-events-core/src/main/java/org/springframework/modulith/events/core/DefaultEventPublication.java

@@ -20,7 +20,7 @@ import java.util.Objects;
 import java.util.Optional;
 import java.util.UUID;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 import org.springframework.util.Assert;
 
 /**

spring-modulith-events/spring-modulith-events-core/src/main/java/org/springframework/modulith/events/core/DefaultEventPublicationRegistry.java

@@ -27,10 +27,10 @@ import java.util.function.Consumer;
 import java.util.function.Predicate;
 import java.util.stream.Stream;
 
+import org.jspecify.annotations.Nullable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.DisposableBean;
-import org.springframework.lang.Nullable;
 import org.springframework.modulith.events.CompletedEventPublications;
 import org.springframework.modulith.events.EventPublication;
 import org.springframework.transaction.annotation.Propagation;

spring-modulith-events/spring-modulith-events-core/src/main/java/org/springframework/modulith/events/core/EventPublicationRegistry.java

@@ -21,8 +21,8 @@ import java.util.function.Consumer;
 import java.util.function.Predicate;
 import java.util.stream.Stream;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.context.ApplicationListener;
-import org.springframework.lang.Nullable;
 import org.springframework.modulith.events.EventPublication;
 
 /**

spring-modulith-events/spring-modulith-events-core/src/main/java/org/springframework/modulith/events/core/PublicationTargetIdentifier.java

@@ -17,7 +17,7 @@ package org.springframework.modulith.events.core;
 
 import java.util.Objects;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 import org.springframework.util.Assert;
 
 /**

spring-modulith-events/spring-modulith-events-core/src/main/java/org/springframework/modulith/events/core/package-info.java

@@ -1,5 +1,5 @@
 /**
  * The event publication registry abstraction.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.modulith.events.core;

spring-modulith-events/spring-modulith-events-core/src/main/java/org/springframework/modulith/events/support/BrokerRouting.java

@@ -15,11 +15,11 @@
  */
 package org.springframework.modulith.events.support;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.expression.EvaluationContext;
 import org.springframework.expression.Expression;
 import org.springframework.expression.common.TemplateParserContext;
 import org.springframework.expression.spel.standard.SpelExpressionParser;
-import org.springframework.lang.Nullable;
 import org.springframework.modulith.events.RoutingTarget;
 import org.springframework.util.Assert;
 

spring-modulith-events/spring-modulith-events-core/src/main/java/org/springframework/modulith/events/support/CompletionRegisteringAdvisor.java

@@ -22,6 +22,8 @@ import java.util.function.Supplier;
 import org.aopalliance.aop.Advice;
 import org.aopalliance.intercept.MethodInterceptor;
 import org.aopalliance.intercept.MethodInvocation;
+import org.jspecify.annotations.NonNull;
+import org.jspecify.annotations.Nullable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.aop.MethodMatcher;
@@ -31,7 +33,6 @@ import org.springframework.aop.support.StaticMethodMatcher;
 import org.springframework.aop.support.annotation.AnnotationMatchingPointcut;
 import org.springframework.core.Ordered;
 import org.springframework.core.annotation.AnnotatedElementUtils;
-import org.springframework.lang.NonNull;
 import org.springframework.modulith.events.core.EventPublicationRegistry;
 import org.springframework.modulith.events.core.PublicationTargetIdentifier;
 import org.springframework.transaction.event.TransactionPhase;
@@ -160,7 +161,7 @@ public class CompletionRegisteringAdvisor extends AbstractPointcutAdvisor {
 		 * @see org.aopalliance.intercept.MethodInterceptor#invoke(org.aopalliance.intercept.MethodInvocation)
 		 */
 		@Override
-		public Object invoke(MethodInvocation invocation) throws Throwable {
+		public @Nullable Object invoke(MethodInvocation invocation) throws Throwable {
 
 			Object result = null;
 			var method = invocation.getMethod();
@@ -232,9 +233,8 @@ public class CompletionRegisteringAdvisor extends AbstractPointcutAdvisor {
 			registry.get().markFailed(event, identifier);
 		}
 
-		@SuppressWarnings("null")
 		private static String lookupListenerId(Method method) {
-			return new TransactionalApplicationListenerMethodAdapter(null, method.getDeclaringClass(), method)
+			return new TransactionalApplicationListenerMethodAdapter("¯\\_(ツ)_/¯", method.getDeclaringClass(), method)
 					.getListenerId();
 		}
 	}

spring-modulith-events/spring-modulith-events-core/src/main/java/org/springframework/modulith/events/support/PersistentApplicationEventMulticaster.java

@@ -19,12 +19,15 @@ import java.lang.reflect.Method;
 import java.time.Duration;
 import java.util.Collection;
 import java.util.List;
+import java.util.Objects;
 import java.util.Optional;
 import java.util.function.Consumer;
 import java.util.function.Predicate;
 import java.util.function.Supplier;
 import java.util.stream.Stream;
 
+import org.jspecify.annotations.NonNull;
+import org.jspecify.annotations.Nullable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.SmartInitializingSingleton;
@@ -36,8 +39,6 @@ import org.springframework.context.event.ApplicationListenerMethodAdapter;
 import org.springframework.core.ResolvableType;
 import org.springframework.core.annotation.AnnotationAwareOrderComparator;
 import org.springframework.core.env.Environment;
-import org.springframework.lang.NonNull;
-import org.springframework.lang.Nullable;
 import org.springframework.modulith.events.EventPublication;
 import org.springframework.modulith.events.IncompleteEventPublications;
 import org.springframework.modulith.events.core.ConditionalEventListener;
@@ -64,10 +65,12 @@ public class PersistentApplicationEventMulticaster extends AbstractApplicationEv
 		implements IncompleteEventPublications, SmartInitializingSingleton {
 
 	private static final Logger LOGGER = LoggerFactory.getLogger(PersistentApplicationEventMulticaster.class);
-	private static final Method LEGACY_SHOULD_HANDLE = ReflectionUtils.findMethod(ApplicationListenerMethodAdapter.class,
-			"shouldHandle", ApplicationEvent.class, Object[].class);
-	private static final Method SHOULD_HANDLE = ReflectionUtils.findMethod(ApplicationListenerMethodAdapter.class,
-			"shouldHandle", ApplicationEvent.class);
+	private static final Method LEGACY_SHOULD_HANDLE = Objects
+			.requireNonNull(ReflectionUtils.findMethod(ApplicationListenerMethodAdapter.class,
+					"shouldHandle", ApplicationEvent.class, Object[].class));
+	private static final Method SHOULD_HANDLE = Objects
+			.requireNonNull(ReflectionUtils.findMethod(ApplicationListenerMethodAdapter.class,
+					"shouldHandle", ApplicationEvent.class));
 
 	static final String REPUBLISH_ON_RESTART = "spring.modulith.events.republish-outstanding-events-on-restart";
 	static final String REPUBLISH_ON_RESTART_LEGACY = "spring.modulith.republish-outstanding-events-on-restart";
@@ -251,16 +254,19 @@ public class PersistentApplicationEventMulticaster extends AbstractApplicationEv
 	 * @param payload the actual payload, must not be {@literal null}.
 	 * @return whether the event should be handled by the given candidate.
 	 */
-	@SuppressWarnings("null")
 	private static boolean invokeShouldHandle(ApplicationListener<?> candidate, ApplicationEvent event, Object payload) {
 
 		if (!(candidate instanceof ApplicationListenerMethodAdapter listener)) {
 			return true;
 		}
 
-		return SHOULD_HANDLE != null
-				? listener.shouldHandle(event)
-				: (boolean) ReflectionUtils.invokeMethod(LEGACY_SHOULD_HANDLE, candidate, event, new Object[] { payload });
+		if (SHOULD_HANDLE != null) {
+			return listener.shouldHandle(event);
+		}
+
+		var result = ReflectionUtils.invokeMethod(LEGACY_SHOULD_HANDLE, candidate, event, new Object[] { payload });
+
+		return result == null ? false : (boolean) result;
 	}
 
 	/**

spring-modulith-events/spring-modulith-events-core/src/main/java/org/springframework/modulith/events/support/package-info.java

@@ -1,5 +1,5 @@
 /**
  * Spring Framework extensions to integrate the event publication registry.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.modulith.events.support;

spring-modulith-events/spring-modulith-events-core/src/test/java/org/springframework/modulith/events/config/EventPublicationAutoConfigurationIntegrationTests.java

@@ -23,6 +23,7 @@ import java.time.Instant;
 import java.time.ZoneId;
 import java.util.function.Function;
 
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.mockito.Mock;
@@ -35,7 +36,6 @@ import org.springframework.boot.test.context.assertj.AssertableApplicationContex
 import org.springframework.boot.test.context.runner.ApplicationContextRunner;
 import org.springframework.boot.test.context.runner.ContextConsumer;
 import org.springframework.context.annotation.AdviceMode;
-import org.springframework.lang.Nullable;
 import org.springframework.modulith.events.CompletedEventPublications;
 import org.springframework.modulith.events.IncompleteEventPublications;
 import org.springframework.modulith.events.config.EventPublicationAutoConfiguration.AsyncPropertiesDefaulter;

spring-modulith-events/spring-modulith-events-jackson/pom.xml

@@ -17,6 +17,11 @@
 
 	<dependencies>
 
+		<dependency>
+			<groupId>org.jspecify</groupId>
+			<artifactId>jspecify</artifactId>
+		</dependency>
+
 		<dependency>
 			<groupId>org.springframework.modulith</groupId>
 			<artifactId>spring-modulith-events-core</artifactId>

spring-modulith-events/spring-modulith-events-jackson/src/main/java/org/springframework/modulith/events/jackson/package-info.java

@@ -1,5 +1,5 @@
 /**
  * A Jackson based implementation of the {@link org.springframework.modulith.events.core.EventSerializer}.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.modulith.events.jackson;

spring-modulith-events/spring-modulith-events-jdbc/pom.xml

@@ -29,6 +29,11 @@
 
 	<dependencies>
 
+		<dependency>
+			<groupId>org.jspecify</groupId>
+			<artifactId>jspecify</artifactId>
+		</dependency>
+
 		<dependency>
 			<groupId>${project.groupId}</groupId>
 			<artifactId>spring-modulith-events-core</artifactId>
@@ -51,7 +56,6 @@
 			<optional>true</optional>
 		</dependency>
 
-
 		<!-- Testing -->
 
 		<dependency>

spring-modulith-events/spring-modulith-events-jdbc/src/main/java/org/springframework/modulith/events/jdbc/DatabaseSchemaInitializer.java

@@ -16,6 +16,7 @@
 package org.springframework.modulith.events.jdbc;
 
 import java.sql.Connection;
+import java.util.Objects;
 
 import javax.sql.DataSource;
 
@@ -39,7 +40,8 @@ class DatabaseSchemaInitializer implements InitializingBean {
 	private final JdbcOperations jdbcOperations;
 	private final JdbcRepositorySettings settings;
 
-	DatabaseSchemaInitializer(DataSource dataSource, ResourceLoader resourceLoader, JdbcOperations jdbcOperations, JdbcRepositorySettings settings) {
+	DatabaseSchemaInitializer(DataSource dataSource, ResourceLoader resourceLoader, JdbcOperations jdbcOperations,
+			JdbcRepositorySettings settings) {
 
 		this.dataSource = dataSource;
 		this.resourceLoader = resourceLoader;
@@ -63,7 +65,7 @@ class DatabaseSchemaInitializer implements InitializingBean {
 
 			if (useSchema) { // A schema name has been specified.
 
-				if (eventPublicationTableExists(schemaName)) {
+				if (eventPublicationTableExists(Objects.requireNonNull(schemaName))) {
 					return;
 				}
 

spring-modulith-events/spring-modulith-events-jdbc/src/main/java/org/springframework/modulith/events/jdbc/JdbcConfigurationProperties.java

@@ -15,10 +15,10 @@
  */
 package org.springframework.modulith.events.jdbc;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.boot.context.properties.ConfigurationProperties;
 import org.springframework.boot.context.properties.bind.ConstructorBinding;
 import org.springframework.boot.context.properties.bind.DefaultValue;
-import org.springframework.lang.Nullable;
 
 /**
  * Configuration properties for JDBC.
@@ -30,7 +30,7 @@ import org.springframework.lang.Nullable;
 class JdbcConfigurationProperties {
 
 	private final SchemaInitialization schemaInitialization;
-	private final String schema;
+	private final @Nullable String schema;
 
 	/**
 	 * Creates a new {@link JdbcConfigurationProperties} instance.
@@ -57,8 +57,7 @@ class JdbcConfigurationProperties {
 	 *
 	 * @return can be {@literal null}.
 	 */
-	@Nullable
-	public String getSchema() {
+	public @Nullable String getSchema() {
 		return schema;
 	}
 

spring-modulith-events/spring-modulith-events-jdbc/src/main/java/org/springframework/modulith/events/jdbc/JdbcEventPublicationRepository.java

@@ -29,11 +29,11 @@ import java.util.function.Supplier;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
+import org.jspecify.annotations.Nullable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.BeanClassLoaderAware;
 import org.springframework.jdbc.core.JdbcOperations;
-import org.springframework.lang.Nullable;
 import org.springframework.modulith.events.core.EventPublicationRepository;
 import org.springframework.modulith.events.core.EventSerializer;
 import org.springframework.modulith.events.core.PublicationTargetIdentifier;
@@ -150,7 +150,7 @@ class JdbcEventPublicationRepository implements EventPublicationRepository, Bean
 			INSERT INTO %s (ID, LISTENER_ID, EVENT_TYPE, SERIALIZED_EVENT, PUBLICATION_DATE, COMPLETION_DATE)
 			SELECT ID, LISTENER_ID, EVENT_TYPE, SERIALIZED_EVENT, PUBLICATION_DATE, ?
 			 	FROM %s
-			 	WHERE ID = ? 
+			 	WHERE ID = ?
 			 	  AND NOT EXISTS (SELECT 1 FROM %s WHERE ID = EVENT_PUBLICATION.ID)
 			""";
 
@@ -161,7 +161,7 @@ class JdbcEventPublicationRepository implements EventPublicationRepository, Bean
 			 	FROM %s
 			 	WHERE LISTENER_ID = ?
 				  AND SERIALIZED_EVENT = ?
-				  AND NOT EXISTS (SELECT 1 FROM %s WHERE ID = EVENT_PUBLICATION.ID) 
+				  AND NOT EXISTS (SELECT 1 FROM %s WHERE ID = EVENT_PUBLICATION.ID)
 			""";
 
 	private static final int DELETE_BATCH_SIZE = 100;
@@ -170,7 +170,7 @@ class JdbcEventPublicationRepository implements EventPublicationRepository, Bean
 	private final EventSerializer serializer;
 	private final JdbcRepositorySettings settings;
 
-	private ClassLoader classLoader;
+	private @Nullable ClassLoader classLoader;
 
 	private final String sqlStatementInsert,
 			sqlStatementFindCompleted,
@@ -222,8 +222,10 @@ class JdbcEventPublicationRepository implements EventPublicationRepository, Bean
 		this.sqlStatementDeleteById = SQL_STATEMENT_DELETE_BY_ID.formatted(table);
 		this.sqlStatementDeleteCompleted = SQL_STATEMENT_DELETE_COMPLETED.formatted(completedTable);
 		this.sqlStatementDeleteCompletedBefore = SQL_STATEMENT_DELETE_COMPLETED_BEFORE.formatted(completedTable);
-		this.sqlStatementCopyToArchive = SQL_STATEMENT_COPY_TO_ARCHIVE_BY_ID.formatted(completedTable, table, completedTable);
-		this.sqlStatementCopyToArchiveByEventAndListenerId = SQL_STATEMENT_COPY_TO_ARCHIVE_BY_EVENT_AND_LISTENER_ID.formatted(completedTable, table, completedTable);
+		this.sqlStatementCopyToArchive = SQL_STATEMENT_COPY_TO_ARCHIVE_BY_ID.formatted(completedTable, table,
+				completedTable);
+		this.sqlStatementCopyToArchiveByEventAndListenerId = SQL_STATEMENT_COPY_TO_ARCHIVE_BY_EVENT_AND_LISTENER_ID
+				.formatted(completedTable, table, completedTable);
 	}
 
 	/*
@@ -342,9 +344,11 @@ class JdbcEventPublicationRepository implements EventPublicationRepository, Bean
 
 	@Override
 	@Transactional(readOnly = true)
-	@SuppressWarnings("null")
 	public List<TargetEventPublication> findIncompletePublications() {
-		return operations.query(sqlStatementFindUncompleted, this::resultSetToPublications);
+
+		var result = operations.query(sqlStatementFindUncompleted, this::resultSetToPublications);
+
+		return result == null ? Collections.emptyList() : result;
 	}
 
 	/*
@@ -428,8 +432,7 @@ class JdbcEventPublicationRepository implements EventPublicationRepository, Bean
 	 * @return can be {@literal null}.
 	 * @throws SQLException
 	 */
-	@Nullable
-	private TargetEventPublication resultSetToPublication(ResultSet rs) throws SQLException {
+	private @Nullable TargetEventPublication resultSetToPublication(ResultSet rs) throws SQLException {
 
 		var id = getUuidFromResultSet(rs);
 		var eventClass = loadClass(id, rs.getString("EVENT_TYPE"));
@@ -456,8 +459,7 @@ class JdbcEventPublicationRepository implements EventPublicationRepository, Bean
 		return settings.getDatabaseType().databaseToUUID(rs.getObject("ID"));
 	}
 
-	@Nullable
-	private Class<?> loadClass(UUID id, String className) {
+	private @Nullable Class<?> loadClass(UUID id, String className) {
 
 		try {
 			return ClassUtils.forName(className, classLoader);

spring-modulith-events/spring-modulith-events-jdbc/src/main/java/org/springframework/modulith/events/jdbc/JdbcRepositorySettings.java

@@ -15,7 +15,7 @@
  */
 package org.springframework.modulith.events.jdbc;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 import org.springframework.modulith.events.support.CompletionMode;
 import org.springframework.util.Assert;
 
@@ -29,7 +29,7 @@ import org.springframework.util.Assert;
 public class JdbcRepositorySettings {
 
 	private final DatabaseType databaseType;
-	private final String schema;
+	private final @Nullable String schema;
 	private final CompletionMode completionMode;
 
 	/**
@@ -67,8 +67,7 @@ public class JdbcRepositorySettings {
 	 *
 	 * @return can be {@literal null}.
 	 */
-	@Nullable
-	public String getSchema() {
+	public @Nullable String getSchema() {
 		return schema;
 	}
 
@@ -82,10 +81,14 @@ public class JdbcRepositorySettings {
 	/**
 	 * Returns whether we use the archiving completion mode.
 	 */
-	public boolean isArchiveCompletion() { return completionMode == CompletionMode.ARCHIVE; }
+	public boolean isArchiveCompletion() {
+		return completionMode == CompletionMode.ARCHIVE;
+	}
 
 	/**
 	 * Returns whether we use the updating completion mode.
 	 */
-	public boolean isUpdateCompletion() { return completionMode == CompletionMode.UPDATE; }
+	public boolean isUpdateCompletion() {
+		return completionMode == CompletionMode.UPDATE;
+	}
 }

spring-modulith-events/spring-modulith-events-jdbc/src/main/java/org/springframework/modulith/events/jdbc/package-info.java

@@ -1,5 +1,5 @@
 /**
  * JDBC integration for {@link org.springframework.modulith.events.core.EventPublicationRepository}.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.modulith.events.jdbc;

spring-modulith-events/spring-modulith-events-jms/pom.xml

@@ -17,6 +17,11 @@
 
 	<dependencies>
 
+		<dependency>
+			<groupId>org.jspecify</groupId>
+			<artifactId>jspecify</artifactId>
+		</dependency>
+
 		<dependency>
 			<groupId>org.springframework.modulith</groupId>
 			<artifactId>spring-modulith-api</artifactId>

spring-modulith-events/spring-modulith-events-jms/src/main/java/org/springframework/modulith/events/jms/package-info.java

@@ -1,5 +1,5 @@
 /**
  * JMS event externalization support.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.modulith.events.jms;

spring-modulith-events/spring-modulith-events-jpa/pom.xml

@@ -18,6 +18,11 @@
 
 	<dependencies>
 
+		<dependency>
+			<groupId>org.jspecify</groupId>
+			<artifactId>jspecify</artifactId>
+		</dependency>
+
 		<dependency>
 			<groupId>${project.groupId}</groupId>
 			<artifactId>spring-modulith-events-core</artifactId>

spring-modulith-events/spring-modulith-events-jpa/src/main/java/org/springframework/modulith/events/jpa/JpaEventPublication.java

@@ -23,6 +23,8 @@ import java.time.Instant;
 import java.util.Objects;
 import java.util.UUID;
 
+import org.jspecify.annotations.NullUnmarked;
+import org.jspecify.annotations.Nullable;
 import org.springframework.modulith.events.jpa.archiving.ArchivedJpaEventPublication;
 import org.springframework.modulith.events.jpa.updating.DefaultJpaEventPublication;
 import org.springframework.modulith.events.support.CompletionMode;
@@ -45,7 +47,7 @@ public abstract class JpaEventPublication {
 	final String serializedEvent;
 	final Class<?> eventType;
 
-	protected Instant completionDate;
+	protected @Nullable Instant completionDate;
 
 	/**
 	 * Creates a new {@link JpaEventPublication} for the given publication date, listener id, serialized event and event
@@ -72,6 +74,7 @@ public abstract class JpaEventPublication {
 		this.eventType = eventType;
 	}
 
+	@NullUnmarked
 	protected JpaEventPublication() {
 
 		this.id = null;

spring-modulith-events/spring-modulith-events-jpa/src/main/java/org/springframework/modulith/events/jpa/JpaEventPublicationRepository.java

@@ -24,6 +24,7 @@ import java.util.Optional;
 import java.util.UUID;
 import java.util.stream.IntStream;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.modulith.events.core.EventPublicationRepository;
 import org.springframework.modulith.events.core.EventSerializer;
 import org.springframework.modulith.events.core.PublicationTargetIdentifier;
@@ -383,7 +384,7 @@ class JpaEventPublicationRepository implements EventPublicationRepository {
 
 		private final JpaEventPublication publication;
 		private final EventSerializer serializer;
-		private Object deserializedEvent;
+		private @Nullable Object deserializedEvent;
 
 		/**
 		 * Creates a new {@link JpaEventPublicationAdapter} for the given {@link JpaEventPublication} and

spring-modulith-events/spring-modulith-events-jpa/src/main/java/org/springframework/modulith/events/jpa/archiving/package-info.java

@@ -0,0 +1,5 @@
+/**
+ * JPA integration for {@link org.springframework.modulith.events.core.EventPublicationRepository}.
+ */
+@org.jspecify.annotations.NullMarked
+package org.springframework.modulith.events.jpa.archiving;

spring-modulith-events/spring-modulith-events-jpa/src/main/java/org/springframework/modulith/events/jpa/package-info.java

@@ -1,5 +1,5 @@
 /**
  * JPA integration for {@link org.springframework.modulith.events.core.EventPublicationRepository}.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.modulith.events.jpa;

spring-modulith-events/spring-modulith-events-jpa/src/main/java/org/springframework/modulith/events/jpa/updating/package-info.java

@@ -0,0 +1,5 @@
+/**
+ * JPA integration for {@link org.springframework.modulith.events.core.EventPublicationRepository}.
+ */
+@org.jspecify.annotations.NullMarked
+package org.springframework.modulith.events.jpa.updating;

spring-modulith-events/spring-modulith-events-kafka/pom.xml

@@ -17,6 +17,11 @@
 
 	<dependencies>
 
+		<dependency>
+			<groupId>org.jspecify</groupId>
+			<artifactId>jspecify</artifactId>
+		</dependency>
+
 		<dependency>
 			<groupId>org.springframework.modulith</groupId>
 			<artifactId>spring-modulith-api</artifactId>

spring-modulith-events/spring-modulith-events-kafka/src/main/java/org/springframework/modulith/events/kafka/KafkaEventExternalizerConfiguration.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.modulith.events.kafka;
 
+import org.jspecify.annotations.NullUnmarked;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.BeanFactory;
@@ -53,6 +54,7 @@ class KafkaEventExternalizerConfiguration {
 	private static final Logger logger = LoggerFactory.getLogger(KafkaEventExternalizerConfiguration.class);
 
 	@Bean
+	@NullUnmarked
 	DelegatingEventExternalizer kafkaEventExternalizer(EventExternalizationConfiguration configuration,
 			KafkaOperations<Object, Object> operations, BeanFactory factory) {
 

spring-modulith-events/spring-modulith-events-kafka/src/main/java/org/springframework/modulith/events/kafka/package-info.java

@@ -1,5 +1,5 @@
 /**
  * Kafka event externalization support.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.modulith.events.kafka;

spring-modulith-events/spring-modulith-events-kafka/src/test/java/org/springframework/modulith/events/kafka/KafkaEventExternalizerConfigurationIntegrationTests.java

@@ -22,12 +22,12 @@ import java.util.Map;
 import java.util.function.Consumer;
 import java.util.function.Supplier;
 
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 import org.mockito.ArgumentCaptor;
 import org.springframework.boot.autoconfigure.AutoConfigurations;
 import org.springframework.boot.test.context.runner.ApplicationContextRunner;
 import org.springframework.kafka.core.KafkaOperations;
-import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.support.MessageBuilder;
 import org.springframework.modulith.events.EventExternalizationConfiguration;

spring-modulith-events/spring-modulith-events-messaging/pom.xml

@@ -17,6 +17,11 @@
 
 	<dependencies>
 
+		<dependency>
+			<groupId>org.jspecify</groupId>
+			<artifactId>jspecify</artifactId>
+		</dependency>
+
 		<dependency>
 			<groupId>org.springframework.modulith</groupId>
 			<artifactId>spring-modulith-api</artifactId>

spring-modulith-events/spring-modulith-events-messaging/src/main/java/org/springframework/modulith/events/messaging/package-info.java

@@ -1,5 +1,5 @@
 /**
  * Messaging event externalization support.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.modulith.events.messaging;

spring-modulith-events/spring-modulith-events-mongodb/pom.xml

@@ -17,6 +17,11 @@
 
 	<dependencies>
 
+		<dependency>
+			<groupId>org.jspecify</groupId>
+			<artifactId>jspecify</artifactId>
+		</dependency>
+
 		<dependency>
 			<groupId>${project.groupId}</groupId>
 			<artifactId>spring-modulith-events-core</artifactId>
@@ -26,6 +31,7 @@
 		<dependency>
 			<groupId>org.springframework.data</groupId>
 			<artifactId>spring-data-mongodb</artifactId>
+			<version>5.0.0-SNAPSHOT</version>
 		</dependency>
 
 		<dependency>

spring-modulith-events/spring-modulith-events-mongodb/src/main/java/org/springframework/modulith/events/mongodb/MongoDbEventPublication.java

@@ -18,9 +18,9 @@ package org.springframework.modulith.events.mongodb;
 import java.time.Instant;
 import java.util.UUID;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.annotation.PersistenceCreator;
 import org.springframework.data.mongodb.core.mapping.Document;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -85,7 +85,6 @@ class MongoDbEventPublication {
 	MongoDbEventPublication markCompleted(Instant instant) {
 
 		Assert.notNull(instant, "Instant must not be null!");
-
 		this.completionDate = instant;
 		return this;
 	}

spring-modulith-events/spring-modulith-events-mongodb/src/main/java/org/springframework/modulith/events/mongodb/package-info.java

@@ -1,5 +1,5 @@
 /**
  * MongoDB integration for {@link org.springframework.modulith.events.core.EventPublicationRepository}.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.modulith.events.mongodb;

spring-modulith-events/spring-modulith-events-neo4j/pom.xml

@@ -17,6 +17,11 @@
 
 	<dependencies>
 
+		<dependency>
+			<groupId>org.jspecify</groupId>
+			<artifactId>jspecify</artifactId>
+		</dependency>
+
 		<dependency>
 			<groupId>${project.groupId}</groupId>
 			<artifactId>spring-modulith-events-core</artifactId>
@@ -59,4 +64,5 @@
 		</dependency>
 
 	</dependencies>
+
 </project>

spring-modulith-events/spring-modulith-events-neo4j/src/main/java/org/springframework/modulith/events/neo4j/Neo4jEventPublication.java

@@ -18,7 +18,7 @@ package org.springframework.modulith.events.neo4j;
 import java.time.Instant;
 import java.util.UUID;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * The event publication entity definition.

spring-modulith-events/spring-modulith-events-neo4j/src/main/java/org/springframework/modulith/events/neo4j/Neo4jEventPublicationRepository.java

@@ -29,6 +29,7 @@ import java.util.UUID;
 import java.util.function.BiFunction;
 import java.util.function.Function;
 
+import org.jspecify.annotations.Nullable;
 import org.neo4j.cypherdsl.core.Cypher;
 import org.neo4j.cypherdsl.core.Node;
 import org.neo4j.cypherdsl.core.ResultStatement;
@@ -40,7 +41,6 @@ import org.neo4j.driver.Values;
 import org.neo4j.driver.types.TypeSystem;
 import org.springframework.data.neo4j.core.Neo4jClient;
 import org.springframework.data.util.Lazy;
-import org.springframework.lang.Nullable;
 import org.springframework.modulith.events.core.EventPublicationRepository;
 import org.springframework.modulith.events.core.EventSerializer;
 import org.springframework.modulith.events.core.PublicationTargetIdentifier;

spring-modulith-events/spring-modulith-events-neo4j/src/main/java/org/springframework/modulith/events/neo4j/package-info.java

@@ -1,5 +1,5 @@
 /**
  * Neo4j integration for {@link org.springframework.modulith.events.core.EventPublicationRepository}.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.modulith.events.neo4j;

spring-modulith-examples/pom.xml

@@ -118,6 +118,11 @@
 
 	<dependencies>
 
+		<dependency>
+			<groupId>org.jspecify</groupId>
+			<artifactId>jspecify</artifactId>
+		</dependency>
+
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter</artifactId>

spring-modulith-examples/spring-modulith-example-epr-jdbc/src/main/java/example/inventory/package-info.java

@@ -4,5 +4,5 @@
  *
  * @see example.inventory.InventoryInternal
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package example.inventory;

spring-modulith-examples/spring-modulith-example-epr-jdbc/src/main/java/example/order/package-info.java

@@ -4,5 +4,5 @@
  *
  * @see example.ModularityTests
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package example.order;

spring-modulith-examples/spring-modulith-example-epr-mongodb/src/main/java/example/inventory/package-info.java

@@ -4,5 +4,5 @@
  *
  * @see example.inventory.InventoryInternal
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package example.inventory;

spring-modulith-examples/spring-modulith-example-epr-mongodb/src/main/java/example/order/package-info.java

@@ -4,5 +4,5 @@
  *
  * @see example.ModularityTests
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package example.order;

spring-modulith-examples/spring-modulith-example-epr-neo4j/src/main/java/example/inventory/package-info.java

@@ -4,5 +4,5 @@
  *
  * @see example.inventory.InventoryInternal
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package example.inventory;

spring-modulith-examples/spring-modulith-example-epr-neo4j/src/main/java/example/order/package-info.java

@@ -4,5 +4,5 @@
  *
  * @see example.ModularityTests
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package example.order;

spring-modulith-examples/spring-modulith-example-full/src/main/java/example/inventory/package-info.java

@@ -4,5 +4,5 @@
  *
  * @see example.inventory.InventoryInternal
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package example.inventory;

spring-modulith-examples/spring-modulith-example-full/src/main/java/example/order/package-info.java

@@ -4,5 +4,5 @@
  *
  * @see example.ModularityTests
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package example.order;

spring-modulith-examples/spring-modulith-example-kafka/src/main/java/example/order/package-info.java

@@ -4,5 +4,5 @@
  *
  * @see example.ModularityTests
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package example.order;

spring-modulith-integration-test/pom.xml

@@ -17,6 +17,11 @@
 
 	<dependencies>
 
+		<dependency>
+			<groupId>org.jspecify</groupId>
+			<artifactId>jspecify</artifactId>
+		</dependency>
+
 		<dependency>
 			<groupId>${project.groupId}</groupId>
 			<artifactId>spring-modulith-core</artifactId>

spring-modulith-junit/pom.xml

@@ -17,6 +17,10 @@
 	</properties>
 
 	<dependencies>
+		<dependency>
+			<groupId>org.jspecify</groupId>
+			<artifactId>jspecify</artifactId>
+		</dependency>
 		<dependency>
 			<groupId>org.eclipse.jgit</groupId>
 			<artifactId>org.eclipse.jgit</artifactId>
@@ -51,5 +55,4 @@
 		</dependency>
 	</dependencies>
 
-
 </project>