本篇文章为大家展示了怎么在Spring Boot中利用@Async实现异步调用，内容简明扼要并且容易理解，绝对能使你眼前一亮，通过这篇文章的详细介绍希望你能有所收获。
定义一个ThreadPoolTaskScheduler线程池：
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
@EnableAsync
@Configuration
class TaskPoolConfig {
@Bean("taskExecutor")
public Executor taskExecutor() {
ThreadPoolTaskScheduler executor = new ThreadPoolTaskScheduler();
executor.setPoolSize(20);
executor.setThreadNamePrefix("taskExecutor-");
return executor;
}
}
}第二步：改造之前的异步任务，让它依赖一个外部资源，比如：Redis
@Slf4j
@Component
public class Task {
@Autowired
private StringRedisTemplate stringRedisTemplate;
@Async("taskExecutor")
public void doTaskOne() throws Exception {
log.info("开始做任务一");
long start = System.currentTimeMillis();
log.info(stringRedisTemplate.randomKey());
long end = System.currentTimeMillis();
log.info("完成任务一，耗时：" + (end - start) + "毫秒");
}
@Async("taskExecutor")
public void doTaskTwo() throws Exception {
log.info("开始做任务二");
long start = System.currentTimeMillis();
log.info(stringRedisTemplate.randomKey());
long end = System.currentTimeMillis();
log.info("完成任务二，耗时：" + (end - start) + "毫秒");
}
@Async("taskExecutor")
public void doTaskThree() throws Exception {
log.info("开始做任务三");
long start = System.currentTimeMillis();
log.info(stringRedisTemplate.randomKey());
long end = System.currentTimeMillis();
log.info("完成任务三，耗时：" + (end - start) + "毫秒");
}
}注意：这里省略了pom.xml中引入依赖和配置redis的步骤
第三步：修改单元测试，模拟高并发情况下ShutDown的情况：
@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
public class ApplicationTests {
@Autowired
private Task task;
@Test
@SneakyThrows
public void test() {
for (int i = 0; i < 10000; i++) {
task.doTaskOne();
task.doTaskTwo();
task.doTaskThree();
if (i == 9999) {
System.exit(0);
}
}
}
}说明：通过for循环往上面定义的线程池中提交任务，由于是异步执行，在执行过程中，利用System.exit(0)来关闭程序，此时由于有任务在执行，就可以观察这些异步任务的销毁与Spring容器中其他资源的顺序是否安全。
第四步：运行上面的单元测试，我们将碰到下面的异常内容。
org.springframework.data.redis.RedisConnectionFailureException: Cannot get Jedis connection; nested exception is redis.clients.jedis.exceptions.JedisConnectionException: Could not get a resource from the pool at org.springframework.data.redis.connection.jedis.JedisConnectionFactory.fetchJedisConnector(JedisConnectionFactory.java:204) ~[spring-data-redis-1.8.10.RELEASE.jar:na] at org.springframework.data.redis.connection.jedis.JedisConnectionFactory.getConnection(JedisConnectionFactory.java:348) ~[spring-data-redis-1.8.10.RELEASE.jar:na] at org.springframework.data.redis.core.RedisConnectionUtils.doGetConnection(RedisConnectionUtils.java:129) ~[spring-data-redis-1.8.10.RELEASE.jar:na] at org.springframework.data.redis.core.RedisConnectionUtils.getConnection(RedisConnectionUtils.java:92) ~[spring-data-redis-1.8.10.RELEASE.jar:na] at org.springframework.data.redis.core.RedisConnectionUtils.getConnection(RedisConnectionUtils.java:79) ~[spring-data-redis-1.8.10.RELEASE.jar:na] at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:194) ~[spring-data-redis-1.8.10.RELEASE.jar:na] at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:169) ~[spring-data-redis-1.8.10.RELEASE.jar:na] at org.springframework.data.redis.core.RedisTemplate.randomKey(RedisTemplate.java:781) ~[spring-data-redis-1.8.10.RELEASE.jar:na] at com.didispace.async.Task.doTaskOne(Task.java:26) ~[classes/:na] at com.didispace.async.Task$$FastClassBySpringCGLIB$$ca3ff9d6.invoke() ~[classes/:na] at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204) ~[spring-core-4.3.14.RELEASE.jar:4.3.14.RELEASE] at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:738) ~[spring-aop-4.3.14.RELEASE.jar:4.3.14.RELEASE] at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157) ~[spring-aop-4.3.14.RELEASE.jar:4.3.14.RELEASE] at org.springframework.aop.interceptor.AsyncExecutionInterceptor$1.call(AsyncExecutionInterceptor.java:115) ~[spring-aop-4.3.14.RELEASE.jar:4.3.14.RELEASE] at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_151] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) [na:1.8.0_151] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) [na:1.8.0_151] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_151] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_151] at java.lang.Thread.run(Thread.java:748) [na:1.8.0_151] Caused by: redis.clients.jedis.exceptions.JedisConnectionException: Could not get a resource from the pool at redis.clients.util.Pool.getResource(Pool.java:53) ~[jedis-2.9.0.jar:na] at redis.clients.jedis.JedisPool.getResource(JedisPool.java:226) ~[jedis-2.9.0.jar:na] at redis.clients.jedis.JedisPool.getResource(JedisPool.java:16) ~[jedis-2.9.0.jar:na] at org.springframework.data.redis.connection.jedis.JedisConnectionFactory.fetchJedisConnector(JedisConnectionFactory.java:194) ~[spring-data-redis-1.8.10.RELEASE.jar:na] ... 19 common frames omitted Caused by: java.lang.InterruptedException: null at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.reportInterruptAfterWait(AbstractQueuedSynchronizer.java:2014) ~[na:1.8.0_151] at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2088) ~[na:1.8.0_151] at org.apache.commons.pool2.impl.LinkedBlockingDeque.pollFirst(LinkedBlockingDeque.java:635) ~[commons-pool2-2.4.3.jar:2.4.3] at org.apache.commons.pool2.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:442) ~[commons-pool2-2.4.3.jar:2.4.3] at org.apache.commons.pool2.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:361) ~[commons-pool2-2.4.3.jar:2.4.3] at redis.clients.util.Pool.getResource(Pool.java:49) ~[jedis-2.9.0.jar:na] ... 22 common frames omitted
如何解决
原因分析
从异常信息JedisConnectionException: Could not get a resource from the pool来看，我们很容易的可以想到，在应用关闭的时候异步任务还在执行，由于Redis连接池先销毁了，导致异步任务中要访问Redis的操作就报了上面的错。所以，我们得出结论，上面的实现方式在应用关闭的时候是不优雅的，那么我们要怎么做呢？
解决方法
要解决上面的问题很简单，Spring的ThreadPoolTaskScheduler为我们提供了相关的配置，只需要加入如下设置即可：
@Bean("taskExecutor")
public Executor taskExecutor() {
ThreadPoolTaskScheduler executor = new ThreadPoolTaskScheduler();
executor.setPoolSize(20);
executor.setThreadNamePrefix("taskExecutor-");
executor.setWaitForTasksToCompleteOnShutdown(true);
executor.setAwaitTerminationSeconds(60);
return executor;
}说明：setWaitForTasksToCompleteOnShutdown（true）该方法就是这里的关键，用来设置线程池关闭的时候等待所有任务都完成再继续销毁其他的Bean，这样这些异步任务的销毁就会先于Redis线程池的销毁。同时，这里还设置了setAwaitTerminationSeconds(60)，该方法用来设置线程池中任务的等待时间，如果超过这个时候还没有销毁就强制销毁，以确保应用最后能够被关闭，而不是阻塞住。
上述内容就是怎么在Spring Boot中利用@Async实现异步调用，你们学到知识或技能了吗？如果还想学到更多技能或者丰富自己的知识储备，欢迎关注创新互联行业资讯频道。
