Spring MVC 的拦截器详解（登录案例实现）

小灰灰 2023-02-14 13:18 4阅读 0赞

Spring MVC中的拦截器（Interceptor）类似于Servlet中的过滤器（Filter），它主要用于拦截用户请求并作相应的处理。例如通过拦截器可以进行权限验证、记录请求信息的日志、判断用户是否登录等。

拦截器的定义

1. 实现HandlerInterceptor接口，或继承HandlerInterceptor接口的实现类（如HandlerInterceptorAdapter）来定义

以实现HandlerInterceptor接口方式为例，自定义拦截器类的代码如下图所示：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQ0OTczMTU5_size_16_color_FFFFFF_t_70]  
拦截器的执行流程

在运行程序时，拦截器的执行是有一定顺序的，该顺序与配置文件中所定义的拦截器的顺序相关。  
单个拦截器，在程序中的执行流程如下图所示：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQ0OTczMTU5_size_16_color_FFFFFF_t_70 1]  
**代码实现方式：**  
创建一个com.lzq.controllor包，新建一个Controllor类

package com.lzq.controller;
    import org.springframework.stereotype.Controller;
    import org.springframework.web.bind.annotation.RequestMapping;
    
    @Controller
    public class HelloController { 
    	@RequestMapping("/hello")
    	public String hello() { 
    		System.out.println("hello!");
    		return "success";
    	}
    }

创建一个com.lzq.Interceptor包，新建一个CustomerInterceptor的类，该类实现HandlerInterceptor接口，重写接口的方法

package com.lzq.Interceptor;
    
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import org.springframework.web.servlet.HandlerInterceptor;
    import org.springframework.web.servlet.ModelAndView;
    
    public class CustomerInterceptor implements HandlerInterceptor { 
    	@Override
    	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
    			throws Exception { 
    		System.out.println("Constomer preHandle");
    		return true;
    	}
    
    	@Override
    	public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
    			ModelAndView modelAndView) throws Exception { 
    		System.out.println("Constomer postHandle");
    	}
    
    	@Override
    	public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
    			throws Exception { 
    		System.out.println("Constomer afterCompletion");
    	}
    }

在新建的web.xml文件，这是web项目当中的配置文件

<?xml version="1.0" encoding="UTF-8"?>
    <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    	 xmlns="http://java.sun.com/xml/ns/javaee" 
    	 xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
    	 	http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" 
    	 	id="WebApp_ID" version="3.0">
    	 	<welcome-file-list>
    	 		<welcome-file>index.jsp</welcome-file>
    	 	</welcome-file-list>
      <servlet>
      
        <servlet-name>springmvc</servlet-name>
        <servlet-class>
                  org.springframework.web.servlet.DispatcherServlet
             </servlet-class>
             
        <init-param>
          <param-name>contextConfigLocation</param-name>
          <param-value>classpath:springmvc-config.xml</param-value>
        </init-param>
        
        <load-on-startup>1</load-on-startup>
      </servlet>
      <servlet-mapping>
        <servlet-name>springmvc</servlet-name>
        <url-pattern>/</url-pattern>
      </servlet-mapping>
    </web-app>

在src当中添加SpringMVC需要的配置文件：配置对应的xml文件

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans"
    	xmlns:mvc="http://www.springframework.org/schema/mvc"
    	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    	xmlns:context="http://www.springframework.org/schema/context"
    	xsi:schemaLocation="http://www.springframework.org/schema/beans
    	   http://www.springframework.org/schema/beans/spring-beans-4.3.xsd
    	   http://www.springframework.org/schema/mvc
    	   http://www.springframework.org/schema/mvc/spring-mvc-4.3.xsd
    	   http://www.springframework.org/schema/context 
      http://www.springframework.org/schema/context/spring-context-4.3.xsd">
    	
    	<context:component-scan
    		base-package="com.lzq.controller" />
    	
    	<bean id="viewResolver"
    		class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    		
    		<property name="prefix" value="/WEB-INF/jsp/" />
    		
    		<property name="suffix" value=".jsp" />
    	</bean>
    	
    	<mvc:interceptors>
    		<bean class="com.lzq.Interceptor.CustomerInterceptor"></bean>
    	</mvc:interceptors>
    </beans>

在WEB-INF文件夹下新建一个jsp文件夹，在里面新建一个success.jsp文件，文件内容自定义。  
对需要的jar包进行添加，如下图：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQ0OTczMTU5_size_16_color_FFFFFF_t_70 2]  
运行项目在控制台当中进行查看：`http://localhost:8080/Interceptor/hello`  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQ0OTczMTU5_size_16_color_FFFFFF_t_70 3]  
多个拦截器（假设有两个拦截器Interceptor1和Interceptor2，并且在配置文件中， Interceptor1拦截器配置在前），在程序中的执行流程如下图所示：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQ0OTczMTU5_size_16_color_FFFFFF_t_70 4]  
**代码实现**  
在前文的基础上添加俩个新的拦截器类，分别为Interceptor1和Interceptor2  
随后在springmvc-config文件当中进行定义：如下图所示：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQ0OTczMTU5_size_16_color_FFFFFF_t_70 5]  
运行项目，打开对应的网址，发送请求：`http://localhost:8080/Interceptor/hello` 在控制台当中查看输出，即方法执行的先后顺序。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQ0OTczMTU5_size_16_color_FFFFFF_t_70 6]  
拦截器的应用案例

在这个案例当中，只有登录后的用户才能访问系统中的主页面，如果没有登录系统而直接访问主页面，则拦截器会将请求拦截，并转发到登录页面，同时在登录页面中给出提示信息。如果用户名或密码错误，也会在登录页面给出相应的提示信息。当已登录的用户在系统主页中单击“退出”链接时，系统同样会回到登录页面。执行流程如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQ0OTczMTU5_size_16_color_FFFFFF_t_70 7]  
**代码实现：**  
第一步：新建一个com.lzq.po包用于储存一个用户对象。对变量进行getter/setter封装，以下代码省略。

package com.lzq.po;
    
    public class User { 
    	private Integer id;
    	private String username;
    	private String password;
    }

第二步：在com.lzq.controller包当中进行创建一个UserController控制器类。实现对应的方法。

package com.lzq.controller;
    
    import javax.servlet.http.HttpSession;
    import org.springframework.stereotype.Controller;
    import org.springframework.ui.Model;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    import com.lzq.po.User;
    
    @Controller
    public class UserController { 
    	@RequestMapping(value = "/login", method = RequestMethod.GET)
    	public String toLogin() { 
    		return "login";
    	}
    
    	@RequestMapping(value = "/login", method = RequestMethod.POST)
    	public String Login(User user, Model model, HttpSession session) { 
    		String username = user.getUsername();
    		String password = user.getPassword();
    		if (username != null & username.equals("huangyueyue") && password != null && password.equals("123456")) { 
    			session.setAttribute("USER", user);
    			return "redirect:main";
    		}
    		model.addAttribute("msg", "账号密码有误，请重新登录！");
    		return "login";
    	}
    
    	@RequestMapping(value = "/main")
    	public String toMain() { 
    		return "main";
    	}
    
    	@RequestMapping(value = "/logout")
    	public String Logout(HttpSession session) { 
    		session.invalidate();
    		return "redirect:login";
    	}
    }

第三步：在com.lzq.Interceptor包当中创建一个拦截器类：

package com.lzq.Interceptor;
    
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    import org.springframework.web.servlet.HandlerInterceptor;
    import org.springframework.web.servlet.ModelAndView;
    import com.lzq.po.User;
    
    public class LoginInterceptor implements HandlerInterceptor { 
    	@Override
    	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
    			throws Exception { 
    		String url = request.getRequestURI();
    		if (url.indexOf("/login")>=0) { 
    			return true;
    		}
    		HttpSession session = request.getSession();
    		User user =(User) session.getAttribute("USER");
    		if (user!=null) { 
    			return true;
    		}
    		request.setAttribute("msg", "账号密码有误，请重新登录！");
    		request.getRequestDispatcher("WEB-INF/jsp/login.jsp").forward(request, response);;
    		return false;
    	}
    
    	@Override
    	public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
    			ModelAndView modelAndView) throws Exception { 
    		
    	}
    
    	@Override
    	public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
    			throws Exception { 
    		
    	}
    }

第四步：对springmvc-config.xml文件进行修改：配置新的拦截器  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQ0OTczMTU5_size_16_color_FFFFFF_t_70 8]  
最后一步：添加相对应的jsp文件：  
main.jsp

<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%>
    <!DOCTYPE html>
    <html>
    <head>
    <meta charset="utf-8">
    <title>main.jsp</title>
    </head>
    <body>
    	当前用户: ${ USER.username}
    	<a href="${pageContext.request.contextPath}/logout">退出</a>
    </body>
    </html>

<%@ page language="java" contentType="text/html; charset=utf-8"
    	pageEncoding="utf-8"%>
    <!DOCTYPE html>
    <html>
    <head>
    <meta charset="utf-8">
    <title>login</title>
    </head>
    <body>
    	${ msg}
    	<form action="${pageContext.request.contextPath}/login" method="POST">
    		用户名: <input type="text" name="username" /><br /> 
    		密    码 :
    		<input type="password" name="password" /><br /> 
    		<input type="submit"value=" 登录" />
    		</form>
    </body>
    </html>

运行项目查看效果：在使用huangyueyue和123456进行登录的时候才会有效果。以及当直接访问`/login`的时候会跳转到`main`  
![在这里插入图片描述][20200603204916824.gif]  
如果你会使用git工具，那么总体的代码案例可在Github当中获取：Https协议地址：`https://github.com/lizuoqun/Gitlzq.git`其中的Interceptor文件夹即为测试案例代码

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[20200603204916824.gif]: https://img-blog.csdnimg.cn/20200603204916824.gif