问题描述
springboot项目中，需要使用到异步调用某个方法，此时 第一个想到的就是 @Async 注解，但是 发现 方法执行报错了，具体报错如下：
java
java.lang.NullPointerException
at com.ruoyi.common.utils.ServletUtils.getRequest(ServletUtils.java:56)
at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:782)
at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:717)
at org.springframework.web.client.RestTemplate.postForObject(RestTemplate.java:443)
at com.ruoyi.web.ecs.service.impl.EcsCollectOperateServiceImpl.collect(EcsCollectOperateServiceImpl.java:42)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:90)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:55)
at java.lang.reflect.Method.invoke(Method.java:508)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:344)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:198)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
at org.springframework.aop.interceptor.AsyncExecutionInterceptor.lambda$invoke$0(AsyncExecutionInterceptor.java:115)
at java.util.concurrent.FutureTask.run(FutureTask.java:277)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1160)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
at java.lang.Thread.run(Thread.java:825)上面日志有点多，其实核心就是这一部分日志：
java
java.lang.NullPointerException
at com.ruoyi.common.utils.ServletUtils.getRequest(ServletUtils.java:56)这块逻辑就是，使用spring底层提供的获取上下文信息的方法。
所以说明 获取不到上下文信息，结果导致报错
解决办法
- 对自定义的配置类 进行改造，原来的配置类是这样的：
java
import java.lang.reflect.Method;
import java.util.concurrent.Executor;
import java.util.concurrent.ThreadPoolExecutor;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler;
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 AsyncConfiguration {
private static final Logger logger = LoggerFactory.getLogger(AsyncConfiguration.class);
@Bean(name = "taskExecutor")
public Executor getAsyncExecutor() {
ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
// 核心线程数：线程池创建时候初始化的线程数
taskExecutor.setCorePoolSize(10);
// 最大线程数：线程池最大的线程数，只有在缓冲队列满了之后才会申请超过核心线程数的线程
taskExecutor.setMaxPoolSize(20);
// 缓冲队列：用来缓冲执行任务的队列
taskExecutor.setQueueCapacity(50);
// 允许线程的空闲时间60秒：当超过了核心线程之外的线程在空闲时间到达之后会被销毁
taskExecutor.setKeepAliveSeconds(60);
// 线程池名的前缀：设置好了之后可以方便我们定位处理任务所在的线程池
taskExecutor.setThreadNamePrefix("HiTask-");
// 缓冲队列满了之后的拒绝策略：由调用线程处理（一般是主线程）
//taskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
taskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.DiscardPolicy());
taskExecutor.initialize();
return taskExecutor;
}
class MyAsyncExceptionHandler implements AsyncUncaughtExceptionHandler {
@Override
public void handleUncaughtException(Throwable throwable, Method method, Object... objects) {
logger.error("MethodName={},Throwable={}",method.getName(),throwable.toString());
}
}
}- 改造之后：
java
import java.lang.reflect.Method;
import java.util.concurrent.Executor;
import java.util.concurrent.ThreadPoolExecutor;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler;
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 org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.RequestContextHolder;
@Configuration
@EnableAsync
public class AsyncConfiguration {
private static final Logger logger = LoggerFactory.getLogger(AsyncConfiguration.class);
@Bean(name = "taskExecutor")
public Executor getAsyncExecutor() {
ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
// 核心线程数：线程池创建时候初始化的线程数
taskExecutor.setCorePoolSize(10);
// 最大线程数：线程池最大的线程数，只有在缓冲队列满了之后才会申请超过核心线程数的线程
taskExecutor.setMaxPoolSize(20);
// 缓冲队列：用来缓冲执行任务的队列
taskExecutor.setQueueCapacity(50);
// 允许线程的空闲时间60秒：当超过了核心线程之外的线程在空闲时间到达之后会被销毁
taskExecutor.setKeepAliveSeconds(60);
// 线程池名的前缀：设置好了之后可以方便我们定位处理任务所在的线程池
taskExecutor.setThreadNamePrefix("HiTask-");
// 缓冲队列满了之后的拒绝策略：由调用线程处理（一般是主线程）
//taskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
taskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.DiscardPolicy());
taskExecutor.initialize();
//解决使用@Async注解，获取不到上下文信息的问题
taskExecutor.setTaskDecorator(runnable -> {
RequestAttributes requestAttributes = RequestContextHolder.currentRequestAttributes();
return ()->{
try {
// 我们set 进去 ,其实是一个ThreadLocal维护的.
RequestContextHolder.setRequestAttributes(requestAttributes);
runnable.run();
} finally {
// 最后记得释放内存
RequestContextHolder.resetRequestAttributes();
}
};
});
return taskExecutor;
}
class MyAsyncExceptionHandler implements AsyncUncaughtExceptionHandler {
@Override
public void handleUncaughtException(Throwable throwable, Method method, Object... objects) {
logger.error("MethodName={},Throwable={}",method.getName(),throwable.toString());
}
}
}总结
解决使用@Async注解，获取不到上下文信息的问题，只需要增加这一段代码即可
java
taskExecutor.setTaskDecorator(runnable -> {
RequestAttributes requestAttributes = RequestContextHolder.currentRequestAttributes();
return ()->{
try {
// 我们set 进去 ,其实是一个ThreadLocal维护的.
RequestContextHolder.setRequestAttributes(requestAttributes);
runnable.run();
} finally {
// 最后记得释放内存
RequestContextHolder.resetRequestAttributes();
}
};
});额外补充一点
如果使用 @Async注解，发现没有生效，那有可能 你没有加 @EnableAsync 注解。
@EnableAsync注解表示 开启异步任务，可以写在springboot的启动类上，也可以写在 配置类上