springboot 正确的在异步线程中使用request的示例代码

    @GetMapping("/getParams")
    public String getParams(String a, int b) {
        return "get success";
    }
    @PostMapping("/postTest")
    public String postTest(HttpServletRequest request,String age, String name) {
        
        new Thread(new Runnable() {
            @Override
            public void run() {
                String age2 = request.getParameter("age");
                String name2 = request.getParameter("name");
                try {
                    Thread.sleep(10);
                } catch (InterruptedException e) {
                    throw new RuntimeException(e);
                }
               String age3 = request.getParameter("age");
               String name3 = request.getParameter("name");
               System.out.println("age1: " + age + " , name1: " + name + " , age2: " + age2 + " , name2: " + name2 + " , age3: " + age3 + " , name3: " + name3);
            }
        }).start();
        return "post success";
    }

org.springframework.web.method.annotation.RequestParamMethodArgumentResolver#resolveName

由于Tomcat中，Request以及Response对象都是会被循环使用的，因此这个时候也是整个Request被重置的时候。

所以根本原因是，在Parameter被重置了之后，didQueryParameters又被置成了true，导致新的请求参数没有被正确解析，就报错了（此时的parameterMap已经被重置，为空）。

而didQueryParameters只有在一种情况下才会被置为true，也就是handleQueryParameters方法被调用时。

而handleQueryParameters会在多个场景中被调用，其中一个就是getParameterValues，获取请求参数的值。

org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter#getDefaultInitBinderArgumentResolvers

private List<HandlerMethodArgumentResolver> getDefaultInitBinderArgumentResolvers() {
	List<HandlerMethodArgumentResolver> resolvers = new ArrayList<>(20);

	// Annotation-based argument resolution
	resolvers.add(new RequestParamMethodArgumentResolver(getBeanFactory(), false));
	resolvers.add(new RequestParamMapMethodArgumentResolver());
	resolvers.add(new PathVariableMethodArgumentResolver());
	resolvers.add(new PathVariableMapMethodArgumentResolver());
	resolvers.add(new MatrixVariableMethodArgumentResolver());
	resolvers.add(new MatrixVariableMapMethodArgumentResolver());
	resolvers.add(new ExpressionValueMethodArgumentResolver(getBeanFactory()));
	resolvers.add(new SessionAttributeMethodArgumentResolver());
	resolvers.add(new RequestAttributeMethodArgumentResolver());

	// Type-based argument resolution
	resolvers.add(new ServletRequestMethodArgumentResolver());
	resolvers.add(new ServletResponseMethodArgumentResolver());

	// Custom arguments
	if (getCustomArgumentResolvers() != null) {
		resolvers.addAll(getCustomArgumentResolvers());
	}

	// Catch-all
	resolvers.add(new PrincipalMethodArgumentResolver());
	resolvers.add(new RequestParamMethodArgumentResolver(getBeanFactory(), true));

	return resolvers;
}

org.apache.coyote.Request#setHook

ASYNC_START

@PostMapping("/postTest")
    public String postTest(HttpServletRequest request, HttpServletResponse response, String age, String name) {
        AsyncContext asyncContext =
                request.isAsyncStarted()
                        ? request.getAsyncContext()
                        : request.startAsync(request, response);
        asyncContext.start(new Runnable() {
            @Override
            public void run() {
                String age2 = request.getParameter("age");
                String name2 = request.getParameter("name");
                try {
                    Thread.sleep(10);
                } catch (InterruptedException e) {
                    throw new RuntimeException(e);
                }
                String age3 = request.getParameter("age");
                String name3 = request.getParameter("name");
                System.out.println("age1: " + age + " , name1: " + name + " , age2: " + age2 + " , name2: " + name2 + " , age3: " + age3 + " , name3: " + name3);
                asyncContext.complete();
            }
        });

        return "post success";
    }