Add Nullable checks.

Resolves #55.

pom.xml

@@ -73,6 +73,7 @@
 		<flapdoodle.version>1.50.5</flapdoodle.version>
 		<hamcrest.version>1.3</hamcrest.version>
 		<jackson.version>2.9.1</jackson.version>
+		<jsr305.version>3.0.2</jsr305.version>
 		<junit.version>4.12</junit.version>
 		<lombok.version>1.18.0</lombok.version>
 		<mockito.version>2.18.3</mockito.version>
@@ -530,6 +531,12 @@
 			</exclusions>
 		</dependency>
 		
+		<dependency>
+			<groupId>com.google.code.findbugs</groupId>
+			<artifactId>jsr305</artifactId>
+			<version>${jsr305.version}</version>
+		</dependency>
+
 		<dependency>
 			<groupId>org.assertj</groupId>
 			<artifactId>assertj-core</artifactId>

src/main/java/org/springframework/session/data/mongo/AbstractMongoSessionConverter.java

@@ -29,6 +29,7 @@ import org.springframework.data.mongodb.core.index.Index;
 import org.springframework.data.mongodb.core.index.IndexInfo;
 import org.springframework.data.mongodb.core.index.IndexOperations;
 import org.springframework.data.mongodb.core.query.Query;
+import org.springframework.lang.Nullable;
 import org.springframework.session.FindByIndexNameSessionRepository;
 import org.springframework.session.Session;
 
@@ -55,6 +56,7 @@ public abstract class AbstractMongoSessionConverter implements GenericConverter
 	 * @param indexValue value to query against
 	 * @return built query or null if indexName is not supported
 	 */
+	@Nullable
 	protected abstract Query getQueryForIndex(String indexName, Object indexValue);
 
 	/**
@@ -95,6 +97,7 @@ public abstract class AbstractMongoSessionConverter implements GenericConverter
 	}
 
 	@SuppressWarnings("unchecked")
+	@Nullable
 	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
 
 		if (source == null) {

src/main/java/org/springframework/session/data/mongo/Assert.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.session.data.mongo;
+
+import org.springframework.lang.Nullable;
+
+/**
+ * @author Greg Turnquist
+ */
+public final class Assert {
+
+	private Assert() {}
+
+	public static <T> T requireNonNull(@Nullable T item, String message) {
+
+		if (item == null) {
+			throw new IllegalArgumentException(message);
+		}
+
+		return item;
+	}
+
+}

src/main/java/org/springframework/session/data/mongo/AuthenticationParser.java

@@ -17,6 +17,7 @@ package org.springframework.session.data.mongo;
 
 import org.springframework.expression.Expression;
 import org.springframework.expression.spel.standard.SpelExpressionParser;
+import org.springframework.lang.Nullable;
 
 /**
  * Utility class to extract principal name from {@code Authentication} object.
@@ -38,7 +39,8 @@ final class AuthenticationParser {
 	 * @param authentication Authentication object
 	 * @return principal name
 	 */
-	static String extractName(Object authentication) {
+	@Nullable
+	static String extractName(@Nullable Object authentication) {
 
 		if (authentication == null) {
 			return null;

src/main/java/org/springframework/session/data/mongo/JacksonMongoSessionConverter.java

@@ -26,6 +26,7 @@ import org.bson.json.JsonMode;
 import org.bson.json.JsonWriterSettings;
 import org.springframework.data.mongodb.core.query.Criteria;
 import org.springframework.data.mongodb.core.query.Query;
+import org.springframework.lang.Nullable;
 import org.springframework.security.jackson2.SecurityJackson2Modules;
 import org.springframework.session.FindByIndexNameSessionRepository;
 import org.springframework.util.Assert;
@@ -72,6 +73,7 @@ public class JacksonMongoSessionConverter extends AbstractMongoSessionConverter
 		this.objectMapper = objectMapper;
 	}
 
+	@Nullable
 	protected Query getQueryForIndex(String indexName, Object indexValue) {
 
 		if (FindByIndexNameSessionRepository.PRINCIPAL_NAME_INDEX_NAME.equals(indexName)) {
@@ -114,6 +116,7 @@ public class JacksonMongoSessionConverter extends AbstractMongoSessionConverter
 	}
 
 	@Override
+	@Nullable
 	protected MongoSession convert(Document source) {
 
 		String json = source.toJson(JsonWriterSettings.builder().outputMode(JsonMode.RELAXED).build());

src/main/java/org/springframework/session/data/mongo/JdkMongoSessionConverter.java

@@ -29,6 +29,7 @@ import org.springframework.core.serializer.support.DeserializingConverter;
 import org.springframework.core.serializer.support.SerializingConverter;
 import org.springframework.data.mongodb.core.query.Criteria;
 import org.springframework.data.mongodb.core.query.Query;
+import org.springframework.lang.Nullable;
 import org.springframework.session.FindByIndexNameSessionRepository;
 import org.springframework.session.Session;
 import org.springframework.util.Assert;
@@ -74,6 +75,7 @@ public class JdkMongoSessionConverter extends AbstractMongoSessionConverter {
 	}
 
 	@Override
+	@Nullable
 	public Query getQueryForIndex(String indexName, Object indexValue) {
 
 		if (FindByIndexNameSessionRepository.PRINCIPAL_NAME_INDEX_NAME.equals(indexName)) {
@@ -130,6 +132,7 @@ public class JdkMongoSessionConverter extends AbstractMongoSessionConverter {
 		return session;
 	}
 
+	@Nullable
 	private byte[] serializeAttributes(Session session) {
 
 		Map<String, Object> attributes = new HashMap<>();
@@ -151,8 +154,10 @@ public class JdkMongoSessionConverter extends AbstractMongoSessionConverter {
 
 		Map<String, Object> attributes = (Map<String, Object>) this.deserializer.convert(attributesBytes);
 
-		for (Map.Entry<String, Object> entry : attributes.entrySet()) {
+		if (attributes != null) {
-			session.setAttribute(entry.getKey(), entry.getValue());
+			for (Map.Entry<String, Object> entry : attributes.entrySet()) {
+				session.setAttribute(entry.getKey(), entry.getValue());
+			}
 		}
 	}
 }

src/main/java/org/springframework/session/data/mongo/MongoOperationsSessionRepository.java

@@ -35,6 +35,7 @@ import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.context.ApplicationEventPublisherAware;
 import org.springframework.data.mongodb.core.MongoOperations;
 import org.springframework.data.mongodb.core.index.IndexOperations;
+import org.springframework.lang.Nullable;
 import org.springframework.session.FindByIndexNameSessionRepository;
 import org.springframework.session.events.SessionCreatedEvent;
 import org.springframework.session.events.SessionDeletedEvent;
@@ -89,10 +90,12 @@ public class MongoOperationsSessionRepository
 
 	@Override
 	public void save(MongoSession session) {
-		this.mongoOperations.save(convertToDBObject(this.mongoSessionConverter, session), this.collectionName);
+		this.mongoOperations.save(Assert.requireNonNull(convertToDBObject(this.mongoSessionConverter, session),
+				"convertToDBObject must not null!"), this.collectionName);
 	}
 
 	@Override
+	@Nullable
 	public MongoSession findById(String id) {
 
 		Document sessionWrapper = findSession(id);
@@ -103,7 +106,7 @@ public class MongoOperationsSessionRepository
 
 		MongoSession session = convertToSession(this.mongoSessionConverter, sessionWrapper);
 
-		if (session.isExpired()) {
+		if (session != null && session.isExpired()) {
 
 			publishEvent(new SessionExpiredEvent(this, session));
 			deleteById(id);
@@ -135,7 +138,12 @@ public class MongoOperationsSessionRepository
 	public void deleteById(String id) {
 
 		Optional.ofNullable(findSession(id)).ifPresent(document -> {
-			publishEvent(new SessionDeletedEvent(this, convertToSession(this.mongoSessionConverter, document)));
+
+			MongoSession session = convertToSession(this.mongoSessionConverter, document);
+			if (session != null) {
+				publishEvent(new SessionDeletedEvent(this, session));
+			}
+
 			this.mongoOperations.remove(document, this.collectionName);
 		});
 	}
@@ -147,6 +155,7 @@ public class MongoOperationsSessionRepository
 		this.mongoSessionConverter.ensureIndexes(indexOperations);
 	}
 
+	@Nullable
 	private Document findSession(String id) {
 		return this.mongoOperations.findById(id, Document.class, this.collectionName);
 	}

src/main/java/org/springframework/session/data/mongo/MongoSession.java

@@ -28,6 +28,7 @@ import java.util.Set;
 import java.util.UUID;
 import java.util.stream.Collectors;
 
+import org.springframework.lang.Nullable;
 import org.springframework.session.Session;
 
 /**
@@ -83,6 +84,7 @@ public class MongoSession implements Session {
 	}
 
 	@Override
+	@Nullable
 	public <T> T getAttribute(String attributeName) {
 		return (T) this.attrs.get(coverDot(attributeName));
 	}

src/main/java/org/springframework/session/data/mongo/MongoSessionUtils.java

@@ -17,6 +17,7 @@ package org.springframework.session.data.mongo;
 
 import org.bson.Document;
 import org.springframework.core.convert.TypeDescriptor;
+import org.springframework.lang.Nullable;
 
 import com.mongodb.DBObject;
 
@@ -25,12 +26,14 @@ import com.mongodb.DBObject;
  */
 public final class MongoSessionUtils {
 
+	@Nullable
 	static DBObject convertToDBObject(AbstractMongoSessionConverter mongoSessionConverter, MongoSession session) {
 
 		return (DBObject) mongoSessionConverter.convert(session, TypeDescriptor.valueOf(MongoSession.class),
 				TypeDescriptor.valueOf(DBObject.class));
 	}
 
+	@Nullable
 	static MongoSession convertToSession(AbstractMongoSessionConverter mongoSessionConverter, Document session) {
 
 		return (MongoSession) mongoSessionConverter.convert(session, TypeDescriptor.valueOf(Document.class),

src/main/java/org/springframework/session/data/mongo/ReactiveMongoOperationsSessionRepository.java

@@ -37,6 +37,8 @@ import org.springframework.session.ReactiveSessionRepository;
 import org.springframework.session.events.SessionCreatedEvent;
 import org.springframework.session.events.SessionDeletedEvent;
 
+import com.mongodb.DBObject;
+
 /**
  * @author Greg Turnquist
  */
@@ -100,8 +102,12 @@ public class ReactiveMongoOperationsSessionRepository
 	@Override
 	public Mono<Void> save(MongoSession session) {
 
-		return this.mongoOperations.save(convertToDBObject(this.mongoSessionConverter, session), this.collectionName)
+		DBObject dbObject = convertToDBObject(this.mongoSessionConverter, session);
-				.then();
+		if (dbObject != null) {
+			return this.mongoOperations.save(dbObject, this.collectionName).then();
+		} else {
+			return Mono.empty();
+		}
 	}
 
 	/**

src/main/java/org/springframework/session/data/mongo/config/annotation/web/http/MongoHttpSessionConfiguration.java

@@ -88,9 +88,13 @@ public class MongoHttpSessionConfiguration extends SpringHttpSessionConfiguratio
 		AnnotationAttributes attributes = AnnotationAttributes
 				.fromMap(importMetadata.getAnnotationAttributes(EnableMongoHttpSession.class.getName()));
 
-		this.maxInactiveIntervalInSeconds = attributes.getNumber("maxInactiveIntervalInSeconds");
+		if (attributes != null) {
+			this.maxInactiveIntervalInSeconds = attributes.getNumber("maxInactiveIntervalInSeconds");
+		} else {
+			this.maxInactiveIntervalInSeconds = MongoOperationsSessionRepository.DEFAULT_INACTIVE_INTERVAL;
+		}
 
-		String collectionNameValue = attributes.getString("collectionName");
+		String collectionNameValue = attributes != null ? attributes.getString("collectionName") : "";
 		if (StringUtils.hasText(collectionNameValue)) {
 			this.collectionName = this.embeddedValueResolver.resolveStringValue(collectionNameValue);
 		}

src/main/java/org/springframework/session/data/mongo/config/annotation/web/http/package-info.java

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * @author Greg Turnquist
+ */
+@NonNullApi
+package org.springframework.session.data.mongo.config.annotation.web.http;
+
+import org.springframework.lang.NonNullApi;

src/main/java/org/springframework/session/data/mongo/config/annotation/web/package-info.java

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * @author Greg Turnquist
+ */
+@NonNullApi
+package org.springframework.session.data.mongo.config.annotation.web;
+
+import org.springframework.lang.NonNullApi;

src/main/java/org/springframework/session/data/mongo/config/annotation/web/reactive/ReactiveMongoWebSessionConfiguration.java

@@ -95,9 +95,13 @@ public class ReactiveMongoWebSessionConfiguration extends SpringWebSessionConfig
 		AnnotationAttributes attributes = AnnotationAttributes
 				.fromMap(importMetadata.getAnnotationAttributes(EnableMongoWebSession.class.getName()));
 
-		this.maxInactiveIntervalInSeconds = attributes.getNumber("maxInactiveIntervalInSeconds");
+		if (attributes != null) {
+			this.maxInactiveIntervalInSeconds = attributes.getNumber("maxInactiveIntervalInSeconds");
+		} else {
+			this.maxInactiveIntervalInSeconds = ReactiveMongoOperationsSessionRepository.DEFAULT_INACTIVE_INTERVAL;
+		}
 
-		String collectionNameValue = attributes.getString("collectionName");
+		String collectionNameValue = attributes != null ? attributes.getString("collectionName") : "";
 		if (StringUtils.hasText(collectionNameValue)) {
 			this.collectionName = this.embeddedValueResolver.resolveStringValue(collectionNameValue);
 		}

src/main/java/org/springframework/session/data/mongo/config/annotation/web/reactive/package-info.java

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * @author Greg Turnquist
+ */
+@NonNullApi
+package org.springframework.session.data.mongo.config.annotation.web.reactive;
+
+import org.springframework.lang.NonNullApi;

src/main/java/org/springframework/session/data/mongo/package-info.java

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * @author Greg Turnquist
+ */
+@NonNullApi
+package org.springframework.session.data.mongo;
+
+import org.springframework.lang.NonNullApi;

src/test/java/org/springframework/session/data/mongo/AbstractMongoSessionConverterTest.java

@@ -22,6 +22,7 @@ import java.time.Duration;
 import org.bson.Document;
 import org.junit.Test;
 import org.springframework.core.convert.TypeDescriptor;
+import org.springframework.lang.Nullable;
 import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
 import org.springframework.security.core.context.SecurityContextImpl;
 import org.springframework.session.FindByIndexNameSessionRepository;
@@ -125,11 +126,13 @@ public abstract class AbstractMongoSessionConverterTest {
 		assertThat(convertedSession.getMaxInactiveInterval()).isEqualTo(Duration.ofMinutes(30));
 	}
 
+	@Nullable
 	MongoSession convertToSession(DBObject session) {
 		return (MongoSession) getMongoSessionConverter().convert(session, TypeDescriptor.valueOf(DBObject.class),
 				TypeDescriptor.valueOf(MongoSession.class));
 	}
 
+	@Nullable
 	DBObject convertToDBObject(MongoSession session) {
 		return (DBObject) getMongoSessionConverter().convert(session, TypeDescriptor.valueOf(MongoSession.class),
 				TypeDescriptor.valueOf(DBObject.class));

src/test/java/org/springframework/session/data/mongo/integration/AbstractClassLoaderTest.java

@@ -25,6 +25,7 @@ import org.springframework.context.ApplicationContext;
 import org.springframework.core.serializer.DefaultDeserializer;
 import org.springframework.core.serializer.support.DeserializingConverter;
 import org.springframework.session.data.mongo.AbstractMongoSessionConverter;
+import org.springframework.session.data.mongo.Assert;
 import org.springframework.session.data.mongo.JdkMongoSessionConverter;
 import org.springframework.util.ReflectionUtils;
 
@@ -43,7 +44,7 @@ public abstract class AbstractClassLoaderTest<T> extends AbstractITest {
 	public void verifyContainerClassLoaderLoadedIntoConverter() {
 
 		Field mongoSessionConverterField = ReflectionUtils.findField(sessionRepository.getClass(), "mongoSessionConverter");
-		ReflectionUtils.makeAccessible(mongoSessionConverterField);
+		ReflectionUtils.makeAccessible(Assert.requireNonNull(mongoSessionConverterField, "mongoSessionConverter must not be null!"));
 		AbstractMongoSessionConverter sessionConverter = (AbstractMongoSessionConverter) ReflectionUtils
 				.getField(mongoSessionConverterField, this.sessionRepository);
 
@@ -63,7 +64,7 @@ public abstract class AbstractClassLoaderTest<T> extends AbstractITest {
 	private static Object extractField(Class<?> clazz, String fieldName, Object obj) {
 
 		Field field = ReflectionUtils.findField(clazz, fieldName);
-		ReflectionUtils.makeAccessible(field);
+		ReflectionUtils.makeAccessible(Assert.requireNonNull(field, fieldName + " must not be null!"));
 		return ReflectionUtils.getField(field, obj);
 	}
 

src/test/java/org/springframework/session/data/mongo/integration/AbstractMongoRepositoryITest.java

@@ -60,7 +60,7 @@ abstract public class AbstractMongoRepositoryITest extends AbstractITest {
 	@Autowired protected MongoOperationsSessionRepository repository;
 
 	@Test
-	public void saves() throws InterruptedException {
+	public void saves() {
 
 		String username = "saves-" + System.currentTimeMillis();
 

src/test/java/org/springframework/session/data/mongo/integration/SessionEventRegistry.java

@@ -24,8 +24,8 @@ import org.springframework.session.events.AbstractSessionEvent;
 
 public class SessionEventRegistry implements ApplicationListener<AbstractSessionEvent> {
 
-	private Map<String, AbstractSessionEvent> events = new HashMap<String, AbstractSessionEvent>();
+	private Map<String, AbstractSessionEvent> events = new HashMap<>();
-	private Map<String, Object> locks = new HashMap<String, Object>();
+	private Map<String, Object> locks = new HashMap<>();
 
 	public void onApplicationEvent(AbstractSessionEvent event) {
 
@@ -67,12 +67,7 @@ public class SessionEventRegistry implements ApplicationListener<AbstractSession
 	private Object getLock(String sessionId) {
 
 		synchronized (this.locks) {
-			Object lock = this.locks.get(sessionId);
+			return this.locks.computeIfAbsent(sessionId, k -> new Object());
-			if (lock == null) {
-				lock = new Object();
-				this.locks.put(sessionId, lock);
-			}
-			return lock;
 		}
 	}
 }