GH-2953: Add NullAway support into the project

Fixes: #2953

* Migrate nullability to JSpecify
* Add `net.ltgt.errorprone` Gradle plugin and respective `NullAway` configuration
* Remove redundant `com.github.spotbugs` since it covered now by the `net.ltgt.errorprone` tool
* Use Java `23` for the latest fixes on Java nullability
* Fix JavaDocs and `this-escape` warnings in the code
* Use `main` for reusable workflows which come already with Java `23`
* Fix all the nullability problems in the project

Author: artembilan

.github/dependabot.yml

@@ -19,7 +19,6 @@ updates:
           - patch
          patterns: 
          - com.gradle.*
-         - com.github.spotbugs
          - io.spring.*
          - org.ajoberstar.grgit
          - org.antora
@@ -28,6 +27,9 @@ updates:
          - org.hibernate.validator:hibernate-validator
          - org.apache.httpcomponents.client5:httpclient5
          - org.awaitility:awaitility
+         - net.ltgt.errorprone
+         - com.uber.nullaway*
+         - com.google.errorprone*
 
   - package-ecosystem: github-actions
     directory: /

.github/workflows/pr-build.yml

@@ -8,4 +8,4 @@ on:
 
 jobs:
   build-pull-request:
-    uses: spring-io/spring-github-workflows/.github/workflows/spring-gradle-pull-request-build.yml@v5
+    uses: spring-io/spring-github-workflows/.github/workflows/spring-gradle-pull-request-build.yml@main

.github/workflows/release.yml

@@ -12,7 +12,9 @@ jobs:
       contents: write
       issues: write
 
-    uses: spring-io/spring-github-workflows/.github/workflows/spring-artifactory-gradle-release.yml@v5
+    uses: spring-io/spring-github-workflows/.github/workflows/spring-artifactory-gradle-release.yml@main
+    with:
+      deployMilestoneToCentral: true
     secrets:
       GH_ACTIONS_REPO_TOKEN: ${{ secrets.GH_ACTIONS_REPO_TOKEN }}
       DEVELOCITY_ACCESS_KEY: ${{ secrets.DEVELOCITY_ACCESS_KEY }}

build.gradle

@@ -19,8 +19,8 @@ plugins {
 	id 'io.spring.dependency-management' version '1.1.7' apply false
 	id 'org.antora' version '1.0.0'
 	id 'io.spring.antora.generate-antora-yml' version '0.0.1'
-	id 'com.github.spotbugs' version '6.1.3'
 	id 'io.freefair.aggregate-javadoc' version '8.11'
+	id 'net.ltgt.errorprone' version '4.1.0' apply false
 }
 
 description = 'Spring AMQP'
@@ -73,12 +73,12 @@ ext {
 antora {
 	version = '3.2.0-alpha.2'
 	playbook = file('src/reference/antora/antora-playbook.yml')
-	options = ['to-dir' : project.layout.buildDirectory.dir('site').get().toString(), clean: true, fetch: !project.gradle.startParameter.offline, stacktrace: true]
+	options = ['to-dir': project.layout.buildDirectory.dir('site').get().toString(), clean: true, fetch: !project.gradle.startParameter.offline, stacktrace: true]
 	dependencies = [
-			'@antora/atlas-extension': '1.0.0-alpha.2',
-			'@antora/collector-extension': '1.0.0-beta.3',
-			'@asciidoctor/tabs': '1.0.0-beta.6',
-			'@springio/antora-extensions': '1.14.2',
+			'@antora/atlas-extension'         : '1.0.0-alpha.2',
+			'@antora/collector-extension'     : '1.0.0-beta.3',
+			'@asciidoctor/tabs'               : '1.0.0-beta.6',
+			'@springio/antora-extensions'     : '1.14.2',
 			'@springio/asciidoctor-extensions': '1.0.0-alpha.14',
 	]
 }
@@ -158,25 +158,42 @@ configure(javaProjects) { subproject ->
 	apply plugin: 'checkstyle'
 	apply plugin: 'kotlin'
 	apply plugin: 'kotlin-spring'
+	apply plugin: 'net.ltgt.errorprone'
 
 	apply from: "${rootProject.projectDir}/gradle/publish-maven.gradle"
 
 	java {
+		toolchain {
+			languageVersion = JavaLanguageVersion.of(23)
+		}
 		withJavadocJar()
 		withSourcesJar()
 		registerFeature('optional') {
 			usingSourceSet(sourceSets.main)
 		}
 	}
 
-	compileJava {
-		options.release = 17
-	}
-
-	compileTestJava {
+	tasks.withType(JavaCompile) {
 		sourceCompatibility = JavaVersion.VERSION_17
-		targetCompatibility = JavaVersion.VERSION_17
 		options.encoding = 'UTF-8'
+		options.errorprone {
+			disableAllChecks = true
+			if (!name.toLowerCase().contains('test')) {
+				option('NullAway:OnlyNullMarked', 'true')
+				option('NullAway:CustomContractAnnotations', 'org.springframework.lang.Contract')
+				option('NullAway:JSpecifyMode', 'true')
+				error('NullAway')
+			}
+		}
+	}
+
+	compileTestKotlin {
+		kotlinOptions {
+			jvmTarget = JavaVersion.VERSION_17
+		}
+		compilerOptions {
+			allWarningsAsErrors = true
+		}
 	}
 
 	eclipse {
@@ -187,10 +204,6 @@ configure(javaProjects) { subproject ->
 
 	// dependencies that are common across all java projects
 	dependencies {
-		def spotbugsAnnotations = "com.github.spotbugs:spotbugs-annotations:${spotbugs.toolVersion.get()}"
-		compileOnly spotbugsAnnotations
-		testCompileOnly spotbugsAnnotations
-
 		testImplementation 'org.apache.logging.log4j:log4j-core'
 		testImplementation "org.hamcrest:hamcrest-core:$hamcrestVersion"
 		testImplementation("org.mockito:mockito-core:$mockitoVersion") {
@@ -211,6 +224,9 @@ configure(javaProjects) { subproject ->
 
 		testImplementation 'org.jetbrains.kotlin:kotlin-reflect'
 		testImplementation 'org.jetbrains.kotlin:kotlin-stdlib-jdk8'
+
+		errorprone 'com.uber.nullaway:nullaway:0.12.3'
+		errorprone 'com.google.errorprone:error_prone_core:2.36.0'
 	}
 
 	// enable all compiler warnings; individual projects may customize further
@@ -430,12 +446,6 @@ project('spring-rabbit') {
 			exclude group: 'org.hamcrest', module: 'hamcrest-core'
 		}
 	}
-
-	compileKotlin {
-		compilerOptions {
-			allWarningsAsErrors = true
-		}
-	}
 }
 
 project('spring-rabbit-stream') {

spring-amqp/src/main/java/org/springframework/amqp/AmqpException.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -16,10 +16,13 @@
 
 package org.springframework.amqp;
 
+import org.jspecify.annotations.Nullable;
+
 /**
  * Base RuntimeException for errors that occur when executing AMQP operations.
  *
  * @author Mark Fisher
+ * @author Artem Bilan
  */
 @SuppressWarnings("serial")
 public class AmqpException extends RuntimeException {
@@ -28,11 +31,11 @@ public AmqpException(String message) {
 		super(message);
 	}
 
-	public AmqpException(Throwable cause) {
+	public AmqpException(@Nullable Throwable cause) {
 		super(cause);
 	}
 
-	public AmqpException(String message, Throwable cause) {
+	public AmqpException(@Nullable String message, @Nullable Throwable cause) {
 		super(message, cause);
 	}
 

spring-amqp/src/main/java/org/springframework/amqp/AmqpRejectAndDontRequeueException.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -16,13 +16,16 @@
 
 package org.springframework.amqp;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Exception for listener implementations used to indicate the
- * basic.reject will be sent with requeue=false in order to enable
- * features such as DLQ.
+ * {@code basic.reject} will be sent with {@code requeue=false}
+ * in order to enable features such as DLQ.
+ *
  * @author Gary Russell
+ * @author Artem Bilan
+ *
  * @since 1.0.1
  *
  */

spring-amqp/src/main/java/org/springframework/amqp/UncategorizedAmqpException.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -16,6 +16,8 @@
 
 package org.springframework.amqp;
 
+import org.jspecify.annotations.Nullable;
+
 /**
  * A "catch-all" exception type within the AmqpException hierarchy
  * when no more specific cause is known.
@@ -25,7 +27,7 @@
 @SuppressWarnings("serial")
 public class UncategorizedAmqpException extends AmqpException {
 
-	public UncategorizedAmqpException(Throwable cause) {
+	public UncategorizedAmqpException(@Nullable Throwable cause) {
 		super(cause);
 	}
 

spring-amqp/src/main/java/org/springframework/amqp/core/AbstractBuilder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2024 the original author or authors.
+ * Copyright 2016-2025 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.
@@ -19,30 +19,34 @@
 import java.util.LinkedHashMap;
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
+
 /**
  * Base class for builders supporting arguments.
  *
  * @author Gary Russell
  * @author Ngoc Nhan
+ * @author Artem Bilan
+ *
  * @since 1.6
  *
  */
 public abstract class AbstractBuilder {
 
-	private Map<String, Object> arguments;
+	private @Nullable Map<String, @Nullable Object> arguments;
 
 	/**
 	 * Return the arguments map, after creating one if necessary.
 	 * @return the arguments.
 	 */
-	protected Map<String, Object> getOrCreateArguments() {
+	protected Map<String, @Nullable Object> getOrCreateArguments() {
 		if (this.arguments == null) {
 			this.arguments = new LinkedHashMap<>();
 		}
 		return this.arguments;
 	}
 
-	protected Map<String, Object> getArguments() {
+	protected @Nullable Map<String, @Nullable Object> getArguments() {
 		return this.arguments;
 	}
 

spring-amqp/src/main/java/org/springframework/amqp/core/AbstractDeclarable.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -25,7 +25,8 @@
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.util.Assert;
 
 /**
@@ -41,7 +42,7 @@ public abstract class AbstractDeclarable implements Declarable {
 
 	private final Lock lock = new ReentrantLock();
 
-	private final Map<String, Object> arguments;
+	protected final Map<String, Object> arguments;
 
 	private boolean shouldDeclare = true;
 
@@ -58,7 +59,7 @@ public AbstractDeclarable() {
 	 * @param arguments the arguments.
 	 * @since 2.2.2
 	 */
-	public AbstractDeclarable(@Nullable Map<String, Object> arguments) {
+	public AbstractDeclarable(@Nullable Map<String, @Nullable Object> arguments) {
 		if (arguments != null) {
 			this.arguments = new HashMap<>(arguments);
 		}
@@ -101,7 +102,8 @@ public void setIgnoreDeclarationExceptions(boolean ignoreDeclarationExceptions)
 	}
 
 	@Override
-	public void setAdminsThatShouldDeclare(@Nullable Object... adminArgs) {
+	@SuppressWarnings("NullAway") // Dataflow analysis limitation
+	public void setAdminsThatShouldDeclare(@Nullable Object @Nullable ... adminArgs) {
 		Collection<Object> admins = new ArrayList<>();
 		if (adminArgs != null) {
 			if (adminArgs.length > 1) {

spring-amqp/src/main/java/org/springframework/amqp/core/AbstractExchange.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -18,6 +18,7 @@
 
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
 
 /**
  * Common properties that describe all exchange types.
@@ -71,7 +72,9 @@ public AbstractExchange(String name, boolean durable, boolean autoDelete) {
 	 * longer in use
 	 * @param arguments the arguments used to declare the exchange
 	 */
-	public AbstractExchange(String name, boolean durable, boolean autoDelete, Map<String, Object> arguments) {
+	public AbstractExchange(String name, boolean durable, boolean autoDelete,
+			@Nullable Map<String, @Nullable Object> arguments) {
+
 		super(arguments);
 		this.name = name;
 		this.durable = durable;