GH-10083: Apply Nullability to core events, leader, message and resource packages

Related to: #10083

* Remove `volatile` and throw exception for illegal state in the `MongoDbMessageStore`

Signed-off-by: Tran Ngoc Nhan <[email protected]>

Author: ngocnhan-tran1996

spring-integration-core/src/main/java/org/springframework/integration/events/IntegrationEvent.java

@@ -33,7 +33,7 @@
 @SuppressWarnings("serial")
 public abstract class IntegrationEvent extends ApplicationEvent {
 
-	protected final Throwable cause; // NOSONAR protected final
+	protected final @Nullable Throwable cause; // NOSONAR protected final
 
 	public IntegrationEvent(Object source) {
 		this(source, null);
@@ -44,8 +44,7 @@ public IntegrationEvent(Object source, @Nullable Throwable cause) {
 		this.cause = cause;
 	}
 
-	@Nullable
-	public Throwable getCause() {
+	public @Nullable Throwable getCause() {
 		return this.cause;
 	}
 

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

@@ -1,4 +1,5 @@
 /**
  * ApplicationEvents generated by the Spring Integration framework.
  */
+@org.jspecify.annotations.NullMarked
 package org.springframework.integration.events;

spring-integration-core/src/main/java/org/springframework/integration/leader/DefaultCandidate.java

@@ -18,6 +18,7 @@
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Simple {@link Candidate} for leadership.
@@ -32,7 +33,7 @@ public class DefaultCandidate extends AbstractCandidate {
 
 	private final Log logger = LogFactory.getLog(getClass());
 
-	private volatile Context leaderContext;
+	private volatile @Nullable Context leaderContext;
 
 	/**
 	 * Instantiate a default candidate.

spring-integration-core/src/main/java/org/springframework/integration/leader/event/AbstractLeaderEvent.java

@@ -16,6 +16,8 @@
 
 package org.springframework.integration.leader.event;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.context.ApplicationEvent;
 import org.springframework.integration.leader.Context;
 
@@ -30,9 +32,9 @@
 @SuppressWarnings("serial")
 public abstract class AbstractLeaderEvent extends ApplicationEvent {
 
-	private final Context context;
+	private final @Nullable Context context;
 
-	private final String role;
+	private final @Nullable String role;
 
 	/**
 	 * Create a new ApplicationEvent.
@@ -50,7 +52,7 @@ public AbstractLeaderEvent(Object source) {
 	 * @param context the context associated with this event
 	 * @param role the role of the leader
 	 */
-	public AbstractLeaderEvent(Object source, Context context, String role) {
+	public AbstractLeaderEvent(Object source, @Nullable Context context, @Nullable String role) {
 		super(source);
 		this.context = context;
 		this.role = role;
@@ -61,7 +63,7 @@ public AbstractLeaderEvent(Object source, Context context, String role) {
 	 *
 	 * @return the context
 	 */
-	public Context getContext() {
+	public @Nullable Context getContext() {
 		return this.context;
 	}
 
@@ -70,7 +72,7 @@ public Context getContext() {
 	 *
 	 * @return the role
 	 */
-	public String getRole() {
+	public @Nullable String getRole() {
 		return this.role;
 	}
 

spring-integration-core/src/main/java/org/springframework/integration/leader/event/DefaultLeaderEventPublisher.java

@@ -16,6 +16,8 @@
 
 package org.springframework.integration.leader.event;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.context.ApplicationEventPublisherAware;
 import org.springframework.integration.leader.Context;
@@ -30,7 +32,7 @@
  */
 public class DefaultLeaderEventPublisher implements LeaderEventPublisher, ApplicationEventPublisherAware {
 
-	private ApplicationEventPublisher applicationEventPublisher;
+	private @Nullable ApplicationEventPublisher applicationEventPublisher;
 
 	/**
 	 * Instantiates a new leader event publisher.

spring-integration-core/src/main/java/org/springframework/integration/leader/event/package-info.java

@@ -1,4 +1,5 @@
 /**
  * Temporary package until s-c-c-core is released.
  */
+@org.jspecify.annotations.NullMarked
 package org.springframework.integration.leader.event;

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

@@ -1,5 +1,5 @@
 /**
  * Temporary package until s-c-c-core is released.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.integration.leader;

spring-integration-core/src/main/java/org/springframework/integration/message/AdviceMessage.java

@@ -19,6 +19,8 @@
 import java.util.Map;
 import java.util.Objects;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageHeaders;
 import org.springframework.messaging.support.GenericMessage;
@@ -81,18 +83,14 @@ public String toString() {
 	}
 
 	@Override
-	public boolean equals(Object o) {
-		if (this == o) {
+	public boolean equals(@Nullable Object o) {
+		if (super.equals(o)) {
 			return true;
 		}
-		if (!(o instanceof AdviceMessage)) {
-			return false;
-		}
-		if (!super.equals(o)) {
-			return false;
+		if (o instanceof AdviceMessage<?> that) {
+			return Objects.equals(this.inputMessage, that.inputMessage);
 		}
-		AdviceMessage<?> that = (AdviceMessage<?>) o;
-		return Objects.equals(this.inputMessage, that.inputMessage);
+		return false;
 	}
 
 	@Override

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

@@ -1,4 +1,5 @@
 /**
  * Provides concrete {@link org.springframework.messaging.Message} implementations.
  */
+@org.jspecify.annotations.NullMarked
 package org.springframework.integration.message;

spring-integration-core/src/main/java/org/springframework/integration/resource/ResourceRetrievingMessageSource.java

@@ -19,6 +19,8 @@
 import java.util.Arrays;
 import java.util.Collection;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;
 import org.springframework.core.io.Resource;
@@ -47,11 +49,13 @@ public class ResourceRetrievingMessageSource extends AbstractMessageSource<Resou
 
 	private final String pattern;
 
-	private volatile ApplicationContext applicationContext;
+	@SuppressWarnings("NullAway.Init")
+	private ApplicationContext applicationContext;
 
-	private volatile ResourcePatternResolver patternResolver;
+	@SuppressWarnings("NullAway.Init")
+	private ResourcePatternResolver patternResolver;
 
-	private volatile CollectionFilter<Resource> filter;
+	private @Nullable CollectionFilter<Resource> filter;
 
 	public ResourceRetrievingMessageSource(String pattern) {
 		Assert.hasText(pattern, "pattern must not be empty");
@@ -85,7 +89,7 @@ protected void onInit() {
 	}
 
 	@Override
-	protected Resource[] doReceive() {
+	protected Resource @Nullable [] doReceive() {
 		try {
 			Resource[] resources = this.patternResolver.getResources(this.pattern);
 			if (ObjectUtils.isEmpty(resources)) {