Today, I want to be the idea of ​​the waterfall flow that passed to the back end after the front end of the MD5 encryption.

I did a SpringMVC interceptor (interceptor) who did not understand Filter and Interceptor and Listener. You can go to this blogger's blog.NapYo

https://blog.csdn.net/qq_34958326/article/details/120535736

Next we analyze the problem through the URL

http://localhost:8080/register/username=12

Among them, the username and 12 in the URL passed to the back end. I believe everyone knows that it is through the request packaging attribute of the HTTP.

The interceptor code is as follows:

@Slf4j
public class LoginInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("----------------helo I am here (LoginInterceptor)!!! -----------------------");
   			log.debug(request.toString());
        return true;

    }
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        //System.out.println ("Posthandle");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        //System.out.println ("After executing aftercompleting");

    }
}

The interceptor is written. We need to write it in webmvcconfigurer. I will simply take the code to everyone

@Configuration
public class LoginConfig implements WebMvcConfigurer {

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new LoginInterceptor())
                .addPathPatterns("/**")
                .excludePathPatterns("/login");
    }
}

We step into the topic

We start to write a break point
We look at the console

I am very happy to see this. There is a value here, click in and see

What is the value of a key and value, but the value still has a value, let's click in to see

Seeing this without "username" -> "12"

We can think of

org.springframework.web.servlet.HandlerMapping.uriTemplateVariables = {key=“org.springframework.web.servlet.HandlerMapping.uriTemplateVariables”,value=“LinkeHashMap”}
We enter the value of the username that we get into LinkhashMap to get

We directly modify the code in the interceptor

First obtain the value of the attribute

// This return is an Object, so the next step is to convert the value of HashMap
request.getAttribute("org.springframework.web.servlet.HandlerMapping.uriTemplateVariables");
// Step 2
HashMap parameter = (HashMap<String,String>)request.getAttribute("org.springframework.web.servlet.HandlerMapping.uriTemplateVariables");
// The third step we can know the value of the attribute value. This is HashMap. We can use get and get the value
 String username = (String)parameter.get("username");
// Last test results

The code is finally posted at the end

@Slf4j
public class LoginInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        
        log.debug(request.toString());
        System.out.println("----------------helo I am here (LoginInterceptor)!!! -----------------------");
        HashMap parameter = (HashMap<String, String>) request.getAttribute("org.springframework.web.servlet.HandlerMapping.uriTemplateVariables");
        String username = (String) parameter.get("username");
        log.debug("------------------------username = " + username + "---------------------");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        //System.out.println ("Posthandle");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        //System.out.println ("After executing aftercompleting");

    }
}

Speak! Intersection Intersection Intersection