In Spring Boot asynchronous tasks, how do child threads access the main thread's Request information?

Spring Boot asynchronous task: Detailed explanation and solution for child thread access to the main thread Request information

In Spring Boot applications, the Controller layer often initiates asynchronous tasks and executes them using thread pools or new threads in the Service layer. However, child threads usually cannot directly access the main thread's HttpServletRequest object, resulting in the inability to obtain request parameters or header information. This article will analyze this problem in depth and provide effective solutions.

Problem description:

Suppose a Spring Boot application, the Controller layer starts a task, and the Service layer uses a new thread to perform specific operations. When the Controller layer returns the response, the child thread cannot obtain the HttpServletRequest information of the main thread.

Error demonstration code (using InheritableThreadLocal):

Even if InheritableThreadLocal is used, the child thread may still not be able to obtain the correct information, because the life cycle of the HttpServletRequest object is bound to the request thread, and the object will be destroyed after the main thread processes the request.

Solution: Avoid dependency on HttpServletRequest

It is unreliable to access HttpServletRequest directly in the child thread. The best practice is to avoid direct dependence on HttpServletRequest in child threads. The necessary request information (such as user ID, request parameters, etc.) should be extracted from HttpServletRequest and passed as parameters to the asynchronous task.

Improved code example:

Controller layer:

 package com.example2.demo.controller;

import javax.servlet.http.HttpServletRequest;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
@RequestMapping(value = "/test")
public class TestController {

    @Autowired
    TestService testService;

    @RequestMapping("/check")
    @ResponseBody
    public void check(HttpServletRequest request) throws Exception {
        String userId = request.getParameter("id"); // Extract necessary data
        System.out.println("id->" userId printed by the parent thread);

        new Thread(() -> {
            testService.doSomething(userId); // Pass data to the service method
        }).start();
        System.out.println("Parent thread method ends");
    }
}

Service layer:

 package com.example2.demo.service;

import org.springframework.stereotype.Service;

@Service
public class TestService {

    public void doSomething(String userId) {
        System.out.println("id->" userId printed by child thread);
        System.out.println("child thread method ends");
        // Perform asynchronous operation using userId
    }
}

In this way, we extract the id parameter in the request and pass it as a parameter to the doSomething method of TestService . The child thread no longer depends on the HttpServletRequest object, thus solving this problem. This is a more robust and reliable way to handle asynchronous tasks. Remember, depending on your actual needs, you need to extract and pass the request information required by all child threads.

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