给方法加上 @Async 注解
package me.deweixu.aysncdemo.service;
public interface AsyncService {
void asyncMethod(String arg);
}
package me.deweixu.aysncdemo.service.ipml;
import me.deweixu.aysncdemo.service.AsyncService;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Service;
@Service
public class AsyncServiceImpl implements AsyncService {
@Async
@Override
public void asyncMethod(String arg) {
System.out.println("arg:" + arg);
System.out.println("=====" + Thread.currentThread().getName() + "=========");
}
}@EnableAsync
在启动类或者配置类加上 @EnableAsync 注解
package me.deweixu.aysncdemo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.scheduling.annotation.EnableAsync;
@EnableAsync
@SpringBootApplication
public class AysncDemoApplication {
public static void main(String[] args) {
SpringApplication.run(AysncDemoApplication.class, args);
}
}测试
package me.deweixu.aysncdemo;
import me.deweixu.aysncdemo.service.AsyncService;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
@RunWith(SpringRunner.class)
@SpringBootTest
public class AysncDemoApplicationTests {
@Autowired
AsyncService asyncService;
@Test
public void testAsync() {
System.out.println("=====" + Thread.currentThread().getName() + "=========");
asyncService.asyncMethod("Async");
}
}=====main=========
2018-03-25 21:30:31.391 INFO 28742 --- [ main] .s.a.AnnotationAsyncExecutionInterceptor : No task executor bean found for async processing: no bean of type TaskExecutor and no bean named 'taskExecutor' either
arg:Async
=====SimpleAsyncTaskExecutor-1=========
从上面的结果看 asyncService.asyncMethod(“Async”) 确实异步执行了，它使用了一个新的线程。
指定 “Executor”
从上面执行的日志可以猜测到 Spring 默认使用 SimpleAsyncTaskExecutor 来异步执行任务的，可以搜索到这个类。 @Async 也可以指定自定义的 Executor。
在启动类中增加自定义的 Executor
package me.deweixu.aysncdemo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
import java.util.concurrent.Executor;
@EnableAsync
@SpringBootApplication
public class AysncDemoApplication {
public static void main(String[] args) {
SpringApplication.run(AysncDemoApplication.class, args);
}
@Bean(name = "threadPoolTaskExecutor")
public Executor threadPoolTaskExecutor() {
return new ThreadPoolTaskExecutor();
}
}指定 “Executor”
package me.deweixu.aysncdemo.service.ipml;
import me.deweixu.aysncdemo.service.AsyncService;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Service;
@Service
public class AsyncServiceImpl implements AsyncService {
@Async("threadPoolTaskExecutor")
@Override
public void asyncMethod(String arg) {
System.out.println("arg:" + arg);
System.out.println("=====" + Thread.currentThread().getName() + "=========");
}
}这样在异步执行任务的时候就使用 threadPoolTaskExecutor
设置默认的
Executor
上面提到如果 @Async 不指定 Executor 就默认使用 SimpleAsyncTaskExecutor，其实默认的 Executor 是可以使用 AsyncConfigurer 接口来配置的
@Configuration
public class SpringAsyncConfig implements AsyncConfigurer {
@Override
public Executor getAsyncExecutor() {
return new ThreadPoolTaskExecutor();
}
}异常捕获
在异步执行的方法中是可能出现异常的，我们可以在任务内部使用 try catch 来处理异常，当任务抛出异常时， Spring 也提供了捕获它的方法。
实现 AsyncUncaughtExceptionHandler 接口
public class CustomAsyncExceptionHandler
implements AsyncUncaughtExceptionHandler {
@Override
public void handleUncaughtException(
Throwable throwable, Method method, Object... obj) {
System.out.println("Exception message - " + throwable.getMessage());
System.out.println("Method name - " + method.getName());
for (Object param : obj) {
System.out.println("Parameter value - " + param);
}
}
}实现 AsyncConfigurer 接口重写 getAsyncUncaughtExceptionHandler 方法
@Configuration
public class SpringAsyncConfig implements AsyncConfigurer {
@Override
public Executor getAsyncExecutor() {
return new ThreadPoolTaskExecutor();
}
@Override
public AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() {
return new CustomAsyncExceptionHandler();
}
}改写 asyncMethod 方法使它抛出异常
@Async
@Override
public void asyncMethod(String arg) {
System.out.println("arg:" + arg);
System.out.println("=====" + Thread.currentThread().getName() + "=========");
throw new NullPointerException();
}运行结果：
=====main=========
arg:Async
=====threadPoolTaskExecutor-1=========
Exception message - Async NullPointerException
Method name - asyncMethod
Parameter value - Async正确捕获到了异常。
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