SpringBoot使用@Async注解实现异步调用

ゞ浴缸里的玫瑰 2023-10-04 08:32 2阅读 0赞

**什么是@Async**  
被@Async标注的方法，称之为异步方法，会被独立的线程所执行，调用者无需等待它执行完毕，也可以执行其他操作。@Async标注在类上，表明类的所有方法都是异步方法

**@Async的具体使用**  
1、在项目启动类上加上@EnableAsync注解，表明开启异步调用  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNTcwODc5_size_16_color_FFFFFF_t_70]  
2、自定义线程池

package com.example.task.config;
    
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.scheduling.annotation.EnableAsync;
    import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
    
    import java.util.concurrent.Executor;
    import java.util.concurrent.ThreadPoolExecutor;
    
    @EnableAsync
    @Configuration
    public class ExecutorConfig {
        
        private static final int CORE_POOL_SIZE=Runtime.getRuntime().availableProcessors();
        private static final int MAX_POOL_SIZE=2*CORE_POOL_SIZE;
        private static final int KEEPALIVE_SECONDS=60;
        private static final int QUERY_CAPACITY=128;
        private static final int AVAIL_TERMINATION_MILLIS=60;
        private static final String THREAD_NAME_PREFIX="TaskExecutor";
    
        @Bean("executor")
        public Executor executor(){
        
            ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
            //核心线程数
            executor.setCorePoolSize(CORE_POOL_SIZE);
            //最大线程数
            executor.setMaxPoolSize(MAX_POOL_SIZE);
            //允许线程的空闲时间
            executor.setKeepAliveSeconds(KEEPALIVE_SECONDS);
            //缓冲队列
            executor.setQueueCapacity(QUERY_CAPACITY);
            //线程的前缀
            executor.setThreadNamePrefix(THREAD_NAME_PREFIX);
            //设置线程中任务的等待时间
            executor.setAwaitTerminationMillis(AVAIL_TERMINATION_MILLIS);
            //线程对拒绝任务的处理策略
            executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
            //线程关闭的时候等待所有任务都完成后再继续销毁其他的bean
            executor.setWaitForTasksToCompleteOnShutdown(true);
    
            return executor;
        }
    }

3、编写异步线程方法

package com.example.task.service;
    
    import org.springframework.scheduling.annotation.Async;
    import org.springframework.scheduling.annotation.AsyncResult;
    import org.springframework.stereotype.Service;
    
    import java.util.concurrent.Future;
    
    @Service
    public class ExecutorTaskService {
        
    
        @Async("executor")
        public Future<String> messages1(){
        
            System.out.println("我是number one");
            return new AsyncResult<>("");
        }
    
        @Async("executor")
        public Future<String> messages2(){
        
            System.out.println("我是number two");
            return new AsyncResult<>("");
        }
    
        @Async("executor")
        public Future<String> messages3(){
        
            System.out.println("我是number three");
            return new AsyncResult<>("");
        }
    }

4、编写控制类，调用异步方法

package com.example.task.controller;
    
    import com.example.task.service.ExecutorTaskService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    @RestController
    public class ExecutorController {
        
    
        @Autowired
        ExecutorTaskService executorTaskService;
    
        @RequestMapping("/task")
        public void getMessage(){
        
            System.err.println("=====================");
            executorTaskService.messages1();
            executorTaskService.messages2();
            executorTaskService.messages3();
        }
    
    }

5、运行程序，对getMessage（）方法进行多次访问，得到的结果如下  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNTcwODc5_size_16_color_FFFFFF_t_70 1]

会发现getMessage（）方法内调用的三个异步方法不是按顺序输出的，证明异步调动生效

这里我是用的很简单的例子来说明@Async是如何使用的，理解用法即可

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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNTcwODc5_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20210324164842878.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNTcwODc5,size_16,color_FFFFFF,t_70