Add support for configuring Jackson's ConstructorDetector

Closes gh-27178

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jackson/JacksonAutoConfiguration.java

@@ -34,6 +34,7 @@ import com.fasterxml.jackson.databind.Module;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.PropertyNamingStrategy;
 import com.fasterxml.jackson.databind.SerializationFeature;
+import com.fasterxml.jackson.databind.cfg.ConstructorDetector;
 import com.fasterxml.jackson.module.paramnames.ParameterNamesModule;
 
 import org.springframework.beans.BeanUtils;
@@ -41,6 +42,7 @@ import org.springframework.beans.factory.BeanFactoryUtils;
 import org.springframework.beans.factory.ListableBeanFactory;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.boot.autoconfigure.jackson.JacksonProperties.ConstructorDetectorStrategy;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.boot.jackson.JsonComponentModule;
 import org.springframework.context.ApplicationContext;
@@ -188,6 +190,7 @@ public class JacksonAutoConfiguration {
 				configureModules(builder);
 				configureLocale(builder);
 				configureDefaultLeniency(builder);
+				configureConstructorDetector(builder);
 			}
 
 			private void configureFeatures(Jackson2ObjectMapperBuilder builder, Map<?, Boolean> features) {
@@ -297,6 +300,27 @@ public class JacksonAutoConfiguration {
 				}
 			}
 
+			private void configureConstructorDetector(Jackson2ObjectMapperBuilder builder) {
+				ConstructorDetectorStrategy strategy = this.jacksonProperties.getConstructorDetector();
+				if (strategy != null) {
+					builder.postConfigurer((objectMapper) -> {
+						switch (strategy) {
+						case USE_PROPERTIES_BASED:
+							objectMapper.setConstructorDetector(ConstructorDetector.USE_PROPERTIES_BASED);
+							break;
+						case USE_DELEGATING:
+							objectMapper.setConstructorDetector(ConstructorDetector.USE_DELEGATING);
+							break;
+						case EXPLICIT_ONLY:
+							objectMapper.setConstructorDetector(ConstructorDetector.EXPLICIT_ONLY);
+							break;
+						default:
+							objectMapper.setConstructorDetector(ConstructorDetector.DEFAULT);
+						}
+					});
+				}
+			}
+
 			private static <T> Collection<T> getBeans(ListableBeanFactory beanFactory, Class<T> type) {
 				return BeanFactoryUtils.beansOfTypeIncludingAncestors(beanFactory, type).values();
 			}

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jackson/JacksonProperties.java

@@ -97,6 +97,12 @@ public class JacksonProperties {
 	 */
 	private Boolean defaultLeniency;
 
+	/**
+	 * Strategy to use to to auto-detect constructor, and in particular behavior with
+	 * single-argument constructors.
+	 */
+	private ConstructorDetectorStrategy constructorDetector;
+
 	/**
 	 * Time zone used when formatting dates. For instance, "America/Los_Angeles" or
 	 * "GMT+10".
@@ -164,6 +170,14 @@ public class JacksonProperties {
 		this.defaultLeniency = defaultLeniency;
 	}
 
+	public ConstructorDetectorStrategy getConstructorDetector() {
+		return this.constructorDetector;
+	}
+
+	public void setConstructorDetector(ConstructorDetectorStrategy constructorDetector) {
+		this.constructorDetector = constructorDetector;
+	}
+
 	public TimeZone getTimeZone() {
 		return this.timeZone;
 	}
@@ -180,4 +194,29 @@ public class JacksonProperties {
 		this.locale = locale;
 	}
 
+	public enum ConstructorDetectorStrategy {
+
+		/**
+		 * Use heuristics to see if "properties" mode is to be used.
+		 */
+		DEFAULT,
+
+		/**
+		 * Assume "properties" mode if not explicitly annotated otherwise.
+		 */
+		USE_PROPERTIES_BASED,
+
+		/**
+		 * Assume "delegating" mode if not explicitly annotated otherwise.
+		 */
+		USE_DELEGATING,
+
+		/**
+		 * Refuse to decide implicit mode and instead throw an InvalidDefinitionException
+		 * for ambiguous cases.
+		 */
+		EXPLICIT_ONLY;
+
+	}
+
 }

spring-boot-project/spring-boot-autoconfigure/src/main/resources/META-INF/additional-spring-configuration-metadata.json

@@ -1048,6 +1048,10 @@
       "name": "spring.integration.jdbc.initialize-schema",
       "defaultValue": "embedded"
     },
+    {
+      "name": "spring.jackson.constructor-detector",
+      "defaultValue": "default"
+    },
     {
       "name": "spring.jackson.joda-date-time-format",
       "type": "java.lang.String",

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/jackson/Jackson211AutoConfigurationTests.java

@@ -54,4 +54,25 @@ public class Jackson211AutoConfigurationTests extends JacksonAutoConfigurationTe
 				});
 	}
 
+	// ConstructorDetector only available as of Jackson 2.12
+	@Override
+	void constructorDetectorWithNoStrategyUseDefault() {
+	}
+
+	@Override
+	void constructorDetectorWithDefaultStrategy() {
+	}
+
+	@Override
+	void constructorDetectorWithUsePropertiesBasedStrategy() {
+	}
+
+	@Override
+	void constructorDetectorWithUseDelegatingStrategy() {
+	}
+
+	@Override
+	void constructorDetectorWithExplicitOnlyStrategy() {
+	}
+
 }

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/jackson/JacksonAutoConfigurationTests.java

@@ -41,6 +41,8 @@ import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.PropertyNamingStrategies.SnakeCaseStrategy;
 import com.fasterxml.jackson.databind.SerializationFeature;
 import com.fasterxml.jackson.databind.SerializerProvider;
+import com.fasterxml.jackson.databind.cfg.ConstructorDetector;
+import com.fasterxml.jackson.databind.cfg.ConstructorDetector.SingleArgConstructor;
 import com.fasterxml.jackson.databind.exc.InvalidFormatException;
 import com.fasterxml.jackson.databind.module.SimpleModule;
 import com.fasterxml.jackson.databind.util.StdDateFormat;
@@ -323,6 +325,62 @@ class JacksonAutoConfigurationTests {
 		});
 	}
 
+	@Test
+	void constructorDetectorWithNoStrategyUseDefault() {
+		this.contextRunner.run((context) -> {
+			ObjectMapper mapper = context.getBean(ObjectMapper.class);
+			ConstructorDetector cd = mapper.getDeserializationConfig().getConstructorDetector();
+			assertThat(cd.singleArgMode()).isEqualTo(SingleArgConstructor.HEURISTIC);
+			assertThat(cd.requireCtorAnnotation()).isFalse();
+			assertThat(cd.allowJDKTypeConstructors()).isFalse();
+		});
+	}
+
+	@Test
+	void constructorDetectorWithDefaultStrategy() {
+		this.contextRunner.withPropertyValues("spring.jackson.constructor-detector=default").run((context) -> {
+			ObjectMapper mapper = context.getBean(ObjectMapper.class);
+			ConstructorDetector cd = mapper.getDeserializationConfig().getConstructorDetector();
+			assertThat(cd.singleArgMode()).isEqualTo(SingleArgConstructor.HEURISTIC);
+			assertThat(cd.requireCtorAnnotation()).isFalse();
+			assertThat(cd.allowJDKTypeConstructors()).isFalse();
+		});
+	}
+
+	@Test
+	void constructorDetectorWithUsePropertiesBasedStrategy() {
+		this.contextRunner.withPropertyValues("spring.jackson.constructor-detector=use-properties-based")
+				.run((context) -> {
+					ObjectMapper mapper = context.getBean(ObjectMapper.class);
+					ConstructorDetector cd = mapper.getDeserializationConfig().getConstructorDetector();
+					assertThat(cd.singleArgMode()).isEqualTo(SingleArgConstructor.PROPERTIES);
+					assertThat(cd.requireCtorAnnotation()).isFalse();
+					assertThat(cd.allowJDKTypeConstructors()).isFalse();
+				});
+	}
+
+	@Test
+	void constructorDetectorWithUseDelegatingStrategy() {
+		this.contextRunner.withPropertyValues("spring.jackson.constructor-detector=use-delegating").run((context) -> {
+			ObjectMapper mapper = context.getBean(ObjectMapper.class);
+			ConstructorDetector cd = mapper.getDeserializationConfig().getConstructorDetector();
+			assertThat(cd.singleArgMode()).isEqualTo(SingleArgConstructor.DELEGATING);
+			assertThat(cd.requireCtorAnnotation()).isFalse();
+			assertThat(cd.allowJDKTypeConstructors()).isFalse();
+		});
+	}
+
+	@Test
+	void constructorDetectorWithExplicitOnlyStrategy() {
+		this.contextRunner.withPropertyValues("spring.jackson.constructor-detector=explicit-only").run((context) -> {
+			ObjectMapper mapper = context.getBean(ObjectMapper.class);
+			ConstructorDetector cd = mapper.getDeserializationConfig().getConstructorDetector();
+			assertThat(cd.singleArgMode()).isEqualTo(SingleArgConstructor.REQUIRE_MODE);
+			assertThat(cd.requireCtorAnnotation()).isFalse();
+			assertThat(cd.allowJDKTypeConstructors()).isFalse();
+		});
+	}
+
 	@Test
 	void additionalJacksonBuilderCustomization() {
 		this.contextRunner.withUserConfiguration(ObjectMapperBuilderCustomConfig.class).run((context) -> {