记一次springboot @Async处理导致后续request请求参数获取为空的坑

背景

近期有个导入excel功能的需求，要求是异步处理导入。于是配置了线程池，使用@Async 异步执行导入方法。做完后发现一个现象，在导入后的接下来的一次请求，接口调用异常。经调试发现后端request未获取到参数（parameterMap大小为0），而实际前端有传值，再次调用同接口后正常。

原因

异步线程使用了request。而request是有生命周期的、复用的，异步线程未处理request的情况下，会被回收复用，导致下一次使用解析不出参数。

解决方法

直接上代码，线程池配置。
关键在于:

HttpServletRequest request = attributes.getRequest();
AsyncContext  asyncContext = request.startAsync();
// 执行任务......
asyncContext .complete();
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AsyncContext complete前request是不会被回收的。

import lombok.Data;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.task.TaskDecorator;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;

import javax.servlet.AsyncContext;
import javax.servlet.http.HttpServletRequest;
import java.util.concurrent.Executor;
import java.util.concurrent.ThreadPoolExecutor;

@Slf4j
@Data
@Configuration
public class ThreadPoolConfig {
    /**
     * 核心线程
     */
    @Value("${jeecg.task.execution.pool.core-size}")
    private int corePoolSize;
    /**
     * 最大线程
     */
    @Value("${jeecg.task.execution.pool.max-size}")
    private int maxPoolSize;
    /**
     * 队列容量
     */
    @Value("${jeecg.task.execution.pool.queue-capacity}")
    private int queueCapacity;
    /**
     * 保持时间
     */
    @Value("${jeecg.task.execution.pool.keep-alive}")
    private int keepAliveSeconds;
    /**
     * 名称前缀
     */
    @Value("${jeecg.task.execution.pool.thread-name-prefix}")
    private String preFix;

    @Bean("asyncServiceExecutor")
    public Executor asyncServiceExecutor() {
        log.info("init asyncServiceExecutor");
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(corePoolSize);
        executor.setMaxPoolSize(maxPoolSize);
        executor.setQueueCapacity(queueCapacity);
        executor.setKeepAliveSeconds(keepAliveSeconds);
        executor.setThreadNamePrefix(preFix);
        executor.setRejectedExecutionHandler( new ThreadPoolExecutor.AbortPolicy());
        executor.setTaskDecorator(new CustomTaskDecorator());
        executor.initialize();
        log.info("asyncServiceExecutor params----corePoolSize:{},maxPoolSize:{},queueCapacity:{},keepAliveSeconds:{},preFix:{}" , corePoolSize,maxPoolSize,queueCapacity,keepAliveSeconds,preFix);
        return executor;
    }


    /**
     * 线程池修饰类
     */
    class CustomTaskDecorator implements TaskDecorator {
        @Override
        public Runnable decorate(Runnable runnable) {
            ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
            AsyncContext asyncContext = null;
            if (attributes!=null) {
                HttpServletRequest request = attributes.getRequest();
                asyncContext = request.startAsync();
            }
            AsyncContext finalAsyncContext = asyncContext;
            return () -> {
                try {
                    RequestContextHolder.setRequestAttributes(attributes,true);
                    runnable.run();
                } finally {
                    RequestContextHolder.resetRequestAttributes();
                    if (finalAsyncContext !=null) {
                        finalAsyncContext.complete();
                    }
                }
            };
        }
    }
}
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