SpringBoot--解决子线程无法获得HttpServletRequest的attribute的问题

我不是女神ヾ 2023-09-29 17:08 0阅读 0赞

原文网址：[SpringBoot--解决子线程无法获得HttpServletRequest的attribute的问题\_IT利刃出鞘的博客-CSDN博客][SpringBoot--_HttpServletRequest_attribute_IT_-CSDN]

## 简介 ##

本文介绍解决SpringBoot子线程无法获得HttpServletRequest的attribute的问题。

在SpringBoot请求中，如果创建了子线程获取request的attribute，会无法获取到。比如：我想记录日志，将日志放到了request的attribute中：request.setAttribute("logContent", "日志内容")，然后创建子线程去获取logContent，然后进行处理。

## 问题复现 ##

**代码**

package com.knife.controller;
    
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.RestController;
    import org.springframework.web.context.request.RequestContextHolder;
    import org.springframework.web.context.request.ServletRequestAttributes;
    
    import javax.servlet.http.HttpServletRequest;
    import java.time.LocalDateTime;
    
    @RestController
    public class HelloController {
    
        @GetMapping("/test")
        public String test() {
            ServletRequestAttributes servletRequestAttributes =
                    (ServletRequestAttributes)RequestContextHolder.getRequestAttributes();
            HttpServletRequest request = servletRequestAttributes.getRequest();
            request.setAttribute("logContent", "日志内容：" + LocalDateTime.now());
    
            Thread thread = new Thread(new Runnable() {
                @Override
                public void run() {
                    ServletRequestAttributes servletRequestAttributes =
                            (ServletRequestAttributes)RequestContextHolder.getRequestAttributes();
                    HttpServletRequest request = servletRequestAttributes.getRequest();
    
                    System.out.println("子线程运行。获取到的attribute为："
                            + request.getAttribute("logContent"));
                }
            });
            thread.start();
    
            return "test success";
        }
    }

结果（getRequestAttributes返回null）

Exception in thread "Thread-131" java.lang.NullPointerException
    	at com.knife.controller.HelloController$1.run(HelloController.java:26)
    	at java.lang.Thread.run(Thread.java:748)

## 解决方案 ##

创建子线程之前调用如下代码：

RequestContextHolder.setRequestAttributes(servletRequestAttributes, true);

**代码**

package com.knife.controller;
    
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.RestController;
    import org.springframework.web.context.request.RequestContextHolder;
    import org.springframework.web.context.request.ServletRequestAttributes;
    
    import javax.servlet.http.HttpServletRequest;
    import java.time.LocalDateTime;
    
    @RestController
    public class HelloController {
    
        @GetMapping("/test")
        public String test() {
            ServletRequestAttributes servletRequestAttributes =
                    (ServletRequestAttributes)RequestContextHolder.getRequestAttributes();
            HttpServletRequest request = servletRequestAttributes.getRequest();
            request.setAttribute("logContent", "日志内容：" + LocalDateTime.now());
    
            RequestContextHolder.setRequestAttributes(servletRequestAttributes, true);
    
            Thread thread = new Thread(new Runnable() {
                @Override
                public void run() {
                    ServletRequestAttributes servletRequestAttributes =
                            (ServletRequestAttributes)RequestContextHolder.getRequestAttributes();
                    HttpServletRequest request = servletRequestAttributes.getRequest();
    
                    System.out.println("子线程运行。获取到的attribute为："
                            + request.getAttribute("logContent"));
                }
            });
            thread.start();
    
            return "test success";
        }
    }

**结果（可以获取到属性）**

子线程运行。获取到的attribute为：日志内容：2022-09-03T16:43:18.463

## 线程安全性 ##

上边的解决方案是否有线程安全问题呢？我在子线程里延时5秒模拟长时间请求，然后多次请求，看结果。如果值都是不一样的话，应该是线程安全的。（本处我无法百分百确定，实际开发中不太建议这么写。实际开发中建议将日志内容作为线程的参数传入，与attribute剥离开）。

**代码**

package com.knife.controller;
    
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.RestController;
    import org.springframework.web.context.request.RequestContextHolder;
    import org.springframework.web.context.request.ServletRequestAttributes;
    
    import javax.servlet.http.HttpServletRequest;
    import java.time.LocalDateTime;
    
    @RestController
    public class HelloController {
    
        @GetMapping("/test")
        public String test() {
            ServletRequestAttributes servletRequestAttributes =
                    (ServletRequestAttributes)RequestContextHolder.getRequestAttributes();
            HttpServletRequest request = servletRequestAttributes.getRequest();
            request.setAttribute("logContent", "日志内容：" + LocalDateTime.now());
    
            RequestContextHolder.setRequestAttributes(servletRequestAttributes, true);
    
            Thread thread = new Thread(new Runnable() {
                @Override
                public void run() {
                    ServletRequestAttributes servletRequestAttributes =
                            (ServletRequestAttributes)RequestContextHolder.getRequestAttributes();
                    HttpServletRequest request = servletRequestAttributes.getRequest();
    
                    System.out.println("子线程运行。获取到的attribute为："
                            + request.getAttribute("logContent"));
    
                    try {
                        Thread.sleep(5000);
                    } catch (InterruptedException e) {
                        throw new RuntimeException(e);
                    }
                }
            });
            thread.start();
    
            return "test success";
        }
    }

**结果（日志内容是新的，应该是线程安全的）**

子线程运行。获取到的attribute为：日志内容：2022-09-03T16:46:42.242
    子线程运行。获取到的attribute为：日志内容：2022-09-03T16:46:42.799
    子线程运行。获取到的attribute为：日志内容：2022-09-03T16:46:43.359
    子线程运行。获取到的attribute为：日志内容：2022-09-03T16:46:43.877
    子线程运行。获取到的attribute为：日志内容：2022-09-03T16:46:44.392
    子线程运行。获取到的attribute为：日志内容：2022-09-03T16:46:44.804
    子线程运行。获取到的attribute为：日志内容：2022-09-03T16:46:45.247
    子线程运行。获取到的attribute为：日志内容：2022-09-03T16:46:45.610
    子线程运行。获取到的attribute为：日志内容：2022-09-03T16:46:46.010
    子线程运行。获取到的attribute为：日志内容：2022-09-03T16:46:46.433

[SpringBoot--_HttpServletRequest_attribute_IT_-CSDN]: https://knife.blog.csdn.net/article/details/126646326