Spring Boot @Async 异步任务执行方法

1、任务执行和调度

spring用taskexecutor和taskscheduler接口提供了异步执行和调度任务的抽象。

spring的taskexecutor和java.util.concurrent.executor接口时一样的，这个接口只有一个方法execute(runnable task)。

1.1、taskexecutor类型

spring已经内置了许多taskexecutor的实现，你没有必要自己去实现：

1. simpleasynctaskexecutor  这种实现不会重用任何线程，每次调用都会创建一个新的线程。
2. synctaskexecutor  这种实现不会异步的执行
3. concurrenttaskexecutor  这种实现是java.util.concurrent.executor的一个adapter。
4. simplethreadpooltaskexecutor  这种实现实际上是quartz的simplethreadpool的一个子类，它监听spring的声明周期回调。
5. threadpooltaskexecutor  这是最常用最通用的一种实现。它包含了java.util.concurrent.threadpoolexecutor的属性，并且用taskexecutor进行包装。

1.2、注解支持调度和异步执行

to enable support for @scheduled and @async annotations add @enablescheduling and @enableasync to one of your

@configuration classes:

@configuration
@enableasync
@enablescheduling
public class appconfig {
}

特别注意

the default advice mode for processing @async annotations is "proxy" which allows for interception of calls through the proxy only; local calls within the same class cannot get intercepted that way. for a more advanced mode of interception, consider switching to "aspectj" mode in combination with compile-time or load-time weaving.

默认是用代理去处理@async的，因此，相同类中的方法调用带@async的方法是无法异步的，这种情况仍然是同步。

举个例子：下面这种，在外部直接调用sayhi()是可以异步执行的，而调用sayhello()时sayhi()仍然是同步执行

public class a {
   public void sayhello() {
    sayhi();
  }

  @async
  public void sayhi() {

  }   
}

1.3、@async注解

在方法上加@async注解表示这是一个异步调用。换句话说，方法的调用者会立即得到返回，并且实际的方法执行是想spring的taskexecutor提交了一个任务。

in other words, the caller will return immediately upon invocation and the actual execution of the method will occur in a task that has been submitted to a spring taskexecutor.

@async
void dosomething() {
  // this will be executed asynchronously
}

@async
void dosomething(string s) {
  // this will be executed asynchronously
}

@async
future<string> returnsomething(int i) {
  // this will be executed asynchronously
}

注意：

@async methods may not only declare a regular java.util.concurrent.future return type but also spring's org.springframework.util.concurrent.listenablefuture or, as of spring 4.2, jdk 8's java.util.concurrent.completablefuture: for richer interaction with the asynchronous task and for immediate composition with further processing steps.

1.4、@async限定executor

默认情况下，当在方法上加@async注解时，将会使用一个支持注解驱动的executor。然而，@async注解的value值可以指定一个别的executor

@async("otherexecutor")
void dosomething(string s) {
  // this will be executed asynchronously by "otherexecutor"
}

这里，otherexecutor是spring容器中任意executor bean的名字。

1.5、@async异常管理

当一个@async方法有一个future类型的返回值时，就很容易管理在调future的get()方法获取任务的执行结果时抛出的异常。如果返回类型是void，那么异常是不会被捕获到的。

public class myasyncuncaughtexceptionhandler implements asyncuncaughtexceptionhandler {

  @override
  public void handleuncaughtexception(throwable ex, method method, object... params) {
    // handle exception
  }
}

2、线程池配置

import org.springframework.context.annotation.bean;
import org.springframework.context.annotation.configuration;
import org.springframework.scheduling.annotation.enableasync;
import org.springframework.scheduling.concurrent.threadpooltaskexecutor;
@configuration
@enableasync
public class taskexecutorconfig {
  private integer corepoolsize = 30;
  private integer maxpoolsize = 50;
  private integer keepaliveseconds = 300;
//  private integer queuecapacity = 2000;
  @bean("mythreadpooltaskexecutor")
  public threadpooltaskexecutor mythreadpooltaskexecutor() {
    threadpooltaskexecutor executor = new threadpooltaskexecutor();
    executor.setcorepoolsize(corepoolsize);
    executor.setmaxpoolsize(maxpoolsize);
    executor.setkeepaliveseconds(keepaliveseconds);
//    executor.setqueuecapacity(queuecapacity);
    executor.setwaitfortaskstocompleteonshutdown(true);
    executor.initialize();
    return executor;
  }
}

调用

@async("mythreadpooltaskexecutor")
  @override
  public void present(couponpresentlogentity entity) {
    try {
      couponbaseresponse rst = couponsendrpcservice.send(entity.getuserid(), entity.getcouponbatchkey(), "1", entity.getvendorid());
      if (null != rst && rst.issuccess()) {
        entity.setstatus(presentstatusenum.success.gettype());
      }else {
        string reason = (null == rst) ? "响应异常" : rst.getmsg();
        entity.setfailurereason(reason);
        entity.setstatus(presentstatusenum.failure.gettype());
      }
    }catch (exception ex) {
      log.error(ex.getmessage(), ex);
      entity.setfailurereason(ex.getmessage());
      entity.setstatus(presentstatusenum.failure.gettype());
    }
    couponpresentlogdao.update(entity);
  }

结果

[info ] 2018-05-09 16:27:39.887 [mythreadpooltaskexecutor-1] [com.ourhours.coupon.rpc.dubbo.receivelogfilter] - receive method-name:send; arguments:[10046031,"4d7cc32f8f7e4b00bca56f6bf4b3b658","1",10001]
[info ] 2018-05-09 16:27:39.889 [mythreadpooltaskexecutor-2] [com.ourhours.coupon.rpc.dubbo.receivelogfilter] - receive method-name:send; arguments:[10046031,"4d7cc32f8f7e4b00bca56f6bf4b3b658","1",10001]

参考：

spring framework reference documentation 4.3.17.release

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。