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Custom interceptor

2022-06-26 09:51:00 【Ma cute's Ma cute】

1、 The project structure is as follows

Insert picture description here

2、 The front-end code is as follows

<body class="text-center">
		<form class="form-signin" method="post" th:action="@{/index}">
			<img class="mb-4" th:src="@{/img/bootstrap-solid.svg}" alt="" width="72" height="72">
			<h1 class="h3 mb-3 font-weight-normal" th:text="#{login.tip}">Please sign in</h1>
			<label style="color: red" th:text="${msg}"></label>
			<label class="sr-only">Username</label>
			<input type="text" name="username" class="form-control" th:placeholder="#{login.username}" required="" autofocus="">
			<label class="sr-only">Password</label>
			<input type="password" name="password" class="form-control" th:placeholder="#{login.password}" required="">
			<div class="checkbox mb-3">
            <input type="checkbox" value="remember-me"> [[#{login.remember}]]
        </label>
			</div>
			<button class="btn btn-lg btn-primary btn-block" type="submit">[[#{login.btn}]]</button>
			<p class="mt-5 mb-3 text-muted"> 2017-2018</p>
			<a class="btn btn-sm" th:href="@{/login.html(l='zh_CN')}"> chinese </a>  <!--thymeleaf No need to ? This method takes the path variable @{/login.html?l='zh_CN'}-->
			<a class="btn btn-sm" th:href="@{/login.html(l='en_US')}">English</a>
		</form>
	</body>

among method="post" Must write , Otherwise, even if the backend uses @PostMapping There will still be a reminder that the request method is wrong , Because the front end doesn't write method=“post”
For the code that displays the message <label style="color: red" th:text="${msg}"></label>, Use label Labels can be dispensed with if Statement to determine when a prompt message is displayed , Is it right to visit a certain page without logging in , Or the login account 、 The password is wrong ！

3、 The back-end code is as follows

（1） Control view jump code

stay WebConfig implements WebMvcConfigurer Next rewrite WebMvcConfigurer Medium addViewControllers Method , Achieve the purpose of controlling view jump

 @Override
    public void addViewControllers(ViewControllerRegistry registry) {
    
        registry.addViewController("/").setViewName("login");
        registry.addViewController("/login.html").setViewName("login");
        registry.addViewController("/main.html").setViewName("dashboard");
    }

（2） Provide service code

@Controller
public class Admin {
    
    @PostMapping("/index")
    public String index(@RequestParam("username") String username, @RequestParam("password") String password, Model model, HttpSession session){
    
        if(!StringUtils.isEmpty(username)&& "ml".equals(username) &&!StringUtils.isEmpty(password)&& "123".equals(password)){
    
            session.setAttribute("loginUser",username);
            return "redirect:/main.html";  // Use redirect:/main.html To redirect to a virtual view , If you jump to template Under the dashboard The account and password will be displayed in the search box 
        }
        else{
    
            model.addAttribute("msg"," Wrong account or password ！ Please login again ！");
            return "login";   // Jump directly to login page 
        }
    }
}

（3）、 To write LoginHandlerInterceptor implements HandlerInterceptor file

package com.ma.ml.config;

import org.springframework.web.servlet.HandlerInterceptor;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class LoginHandlerInterceptor implements HandlerInterceptor {
    
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
    
        HttpSession session = request.getSession();
        Object loginUser = session.getAttribute("loginUser");
        if(loginUser==null){
    
            request.setAttribute("msg"," Please log in first ！");
            request.getRequestDispatcher("/").forward(request,response);
            return false;
        }
        else {
    
            return true;
        }
    }
}

（4）、 stay WebConfig implements WebMvcConfigurer Add your own defined interceptors in , Customize which static resources to intercept

@Override
    public void addInterceptors(InterceptorRegistry registry) {
    
        registry.addInterceptor(new LoginHandlerInterceptor())
                .addPathPatterns("/**")
                .excludePathPatterns("/","/login.html","/index","/css/**","/js/**","/img/**");
    }

4、WebConfig All the codes in are as follows


@Configuration
public class WebConfig implements WebMvcConfigurer {
    
    @Override
    public void addViewControllers(ViewControllerRegistry registry) {
    
        registry.addViewController("/").setViewName("login");
        registry.addViewController("/login.html").setViewName("login");
        registry.addViewController("/main.html").setViewName("dashboard");
    }
    @Bean   // Register in container 
    public LocaleResolver localeResolver(){
    
        return  new MyLocalResolver();
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
    
        registry.addInterceptor(new LoginHandlerInterceptor())
                .addPathPatterns("/**")
                .excludePathPatterns("/","/login.html","/index","/css/**","/js/**","/img/**");
    }

}

5、 Demo login

Direct access main.html The path of , Prompt to log in first . Because I haven't logged in at this time ,session There is no login information in , So you can only access after logging in main.html The next path dashboard Front page
Insert picture description here
After password login session There is loginUser Not empty , So you can access main.html The next path dashboard Front page