概述

Spring Boot关于任务执行的自动配置类。主要是确保容器中存在两个bean组件 :
1. TaskExecutorBuilder taskExecutorBuilder – TaskExecutor构建器
2. ThreadPoolTaskExecutor applicationTaskExecutor,带有别名taskExecutor – 异步任务,调度任务执行的基础组件

源代码

源代码版本 : spring-boot-autoconfigure-2.1.3.RELEASE

package org.springframework.boot.autoconfigure.task;

// 省略 import 行

/**
 * EnableAutoConfiguration Auto-configuration for TaskExecutor.
 *
 * @author Stephane Nicoll
 * @author Camille Vienot
 * @since 2.1.0
 */
 // 仅在类 ThreadPoolTaskExecutor 存在于 classpath 时才应用
@ConditionalOnClass(ThreadPoolTaskExecutor.class)
@Configuration
// 确保前缀为 spring.task.execution 的属性配置项被加载到 bean TaskExecutionProperties 中
@EnableConfigurationProperties(TaskExecutionProperties.class)
public class TaskExecutionAutoConfiguration {

	/**
	 * Bean name of the application TaskExecutor.
	 */
	public static final String APPLICATION_TASK_EXECUTOR_BEAN_NAME = "applicationTaskExecutor";

	private final TaskExecutionProperties properties;

	private final ObjectProvider<TaskExecutorCustomizer> taskExecutorCustomizers;

	private final ObjectProvider<TaskDecorator> taskDecorator;

	public TaskExecutionAutoConfiguration(TaskExecutionProperties properties,
			ObjectProvider<TaskExecutorCustomizer> taskExecutorCustomizers,
			ObjectProvider<TaskDecorator> taskDecorator) {
		this.properties = properties;
		this.taskExecutorCustomizers = taskExecutorCustomizers;
		this.taskDecorator = taskDecorator;
	}

    // 定义 bean TaskExecutorBuilder taskExecutorBuilder
    // 这是一个 TaskExecutor 构建器
	@Bean
    // 仅在该 bean 尚未被定义时才定义
	@ConditionalOnMissingBean
	public TaskExecutorBuilder taskExecutorBuilder() {
		TaskExecutionProperties.Pool pool = this.properties.getPool();
		TaskExecutorBuilder builder = new TaskExecutorBuilder();
		builder = builder.queueCapacity(pool.getQueueCapacity());
		builder = builder.corePoolSize(pool.getCoreSize());
		builder = builder.maxPoolSize(pool.getMaxSize());
		builder = builder.allowCoreThreadTimeOut(pool.isAllowCoreThreadTimeout());
		builder = builder.keepAlive(pool.getKeepAlive());
		builder = builder.threadNamePrefix(this.properties.getThreadNamePrefix());
		builder = builder.customizers(this.taskExecutorCustomizers);
		builder = builder.taskDecorator(this.taskDecorator.getIfUnique());
		return builder;
	}

    // 懒惰模式定义 bean ThreadPoolTaskExecutor applicationTaskExecutor，
    // 基于容器中存在的  TaskExecutorBuilder
	@Lazy
    // 使用bean名称 : taskExecutor, applicationTaskExecutor
	@Bean(name = { APPLICATION_TASK_EXECUTOR_BEAN_NAME,
			AsyncAnnotationBeanPostProcessor.DEFAULT_TASK_EXECUTOR_BEAN_NAME })
    // 仅在容器中不存在类型为 Executor 的 bean 时才定义            
	@ConditionalOnMissingBean(Executor.class)
	public ThreadPoolTaskExecutor applicationTaskExecutor(TaskExecutorBuilder builder) {
		return builder.build();
	}

}