13COM.NET

第一种情况，Service类：

@Async
public String test1() {
    String threadName = Thread.currentThread().getName();
    log.error("{}: 1 start", threadName);
    try {
        Thread.sleep(5000L);
    } catch (Exception e){
    }
    log.error("{}: 1 end", threadName);
    return "s1";
}

@Async
public String test2() {
    String threadName = Thread.currentThread().getName();
    log.error("{}: 2 start", threadName);
    try {
        Thread.sleep(2000L);
    } catch (Exception e){
    }
    log.error("{}: 2 end", threadName);
    return "s2";
}

Controller类：

try {
    String threadName = Thread.currentThread().getName();
    log.error("{}: 0 start", threadName);
    PrintWriter out = response.getWriter();
    String f1 = testService.test1();
    String f2 = testService.test2();
    log.error("{}: 0 end {} {}", threadName, f1, f2);

} catch (Exception e) {
}

 

结果是，test1和test2在不同线程被执行，然而对test1和test2的调用，立刻结束，f1和f2都是null。

也就是说，这样可以独立执行两个后台任务，然而并不能等待返回结果，怎样才能得到结果呢？

 

第二种情况，Service类：

@Async
public Future<String> test1() {
    String threadName = Thread.currentThread().getName();
    log.error("{}: 1 start", threadName);
    try {
        Thread.sleep(5000L);
    } catch (Exception e){
    }
    log.error("{}: 1 end", threadName);
    return new AsyncResult<>("s1");
}

@Async
public Future<String> test2() {
    String threadName = Thread.currentThread().getName();
    log.error("{}: 2 start", threadName);
    try {
        Thread.sleep(2000L);
    } catch (Exception e){
    }
    log.error("{}: 2 end", threadName);
    return new AsyncResult<>("s2");
}

 

Controller类：

try {
    String threadName = Thread.currentThread().getName();
    log.error("{}: 0 start", threadName);
    PrintWriter out = response.getWriter();
    Future<String> f1 = testService.test1();
    Future<String> f2 = testService.test2();
    
    log.error("{}: 0 end {} {}", threadName, f1.get(), f2.get());
} catch (Exception e) {
}

这样可以正确得到结果。Futrue<T>和AsyncResult<T>让调用线程可以join，等待Future结果。