How does Spring Boot child thread access request information of the main thread?

How does Spring Boot child thread safely access main thread request information

In Spring Boot application, the controller layer initiates asynchronous tasks, and when the Service layer uses a new thread to process, it often faces the problem that the child thread cannot access the main thread HttpServletRequest object. This is because HttpServletRequest is bound to the main thread lifecycle and the child thread cannot be accessed directly. This article analyzes this problem and provides a reliable solution.

Problem description:

Use InheritableThreadLocal<httpservletrequest></httpservletrequest> directly InheritableThreadLocal<httpservletrequest></httpservletrequest> Passing HttpServletRequest to the child thread is unreliable because the HttpServletRequest object may have been destroyed after the main thread has processed the request. Even if the delivery is successful, it can cause memory leaks or other problems.

Error demonstration (code snippet):

The following code tries to pass HttpServletRequest using InheritableThreadLocal , but the child thread cannot get the correct user information:

Controller:

@RestController
@RequestMapping("/test")
public class TestController {

    private static InheritableThreadLocal<httpservletrequest> requestHolder = new InheritableThreadLocal();

    @Autowired
    private TestService testService;

    @GetMapping("/check")
    public void check(HttpServletRequest request) {
        String userId = request.getHeader("userId");
        System.out.println("main thread userId: " userId);
        requestHolder.set(request);
        new Thread(() -> testService.doSomething()).start();
        System.out.println("main thread end");
    }
}</httpservletrequest>

Service layer:

@Service
public class TestService {
    public void doSomething() {
        HttpServletRequest request = requestHolder.get();
        String userId = request != null ? request.getHeader("userId") : "null";
        System.out.println("child thread userId: " userId);
    }
}

Solution:

Avoid passing HttpServletRequest objects directly. The best practice is to extract necessary information (such as userId ) from HttpServletRequest and then store this information in InheritableThreadLocal .

Improved code example:

Controller:

@RestController
@RequestMapping("/test")
public class TestController {

    private static InheritableThreadLocal<string> userIdHolder = new InheritableThreadLocal();

    @Autowired
    private TestService testService;

    @GetMapping("/check")
    public void check(HttpServletRequest request) {
        String userId = request.getHeader("userId");
        System.out.println("main thread userId: " userId);
        userIdHolder.set(userId);
        new Thread(() -> testService.doSomething()).start();
        System.out.println("main thread end");
    }
}</string>

Service layer:

@Service
public class TestService {
    public void doSomething() {
        String userId = userIdHolder.get();
        System.out.println("child thread userId: " userId);
    }
}

This improved version only passes userId , avoiding the life cycle of HttpServletRequest object and ensuring that the child thread can reliably access the required data. According to actual needs, other necessary information can also be stored in InheritableThreadLocal . Remember to clear the data in InheritableThreadLocal in time after use to avoid memory leakage.

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