SpringMVC拦截器原理及实现

矫情吗；* 2024-04-18 18:36 70阅读 0赞

# 1、拦截器概念 #

Spring MVC 的拦截器类似于Servlet 开发中的过滤器Filter，用于对Controller进行预处理和后处理。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc4NDY3Mw_size_16_color_FFFFFF_t_70]

# 2、使用SpringMVC拦截器步骤: #

### 2.1 新建拦截器类 ###

**功能：定义处理逻辑，拦截到之后如何处理**  
拦截器方法的执行时机:  
1):preHandle:控制器方法执行之前执行,返回结果为true表示放行,如果返回为false,表示拦截(可以做权限拦截,登录检查拦截).  
2):postHandle:控制器方法执行后,视图渲染之前执行(可以加入统一的响应信息).  
3):afterCompletion:视图渲染之后执行(处理Controller异常信息,记录操作日志，清理资源等)

#### 方式一：实现HandlerInterceptor接口（推荐） ####

实现接口 org.springframework.web.servlet.HandlerInterceptor

public class MyInterceptor implements HandlerInterceptor{
    
    
        @Override
        //前置拦截(一般情况下只配置前置拦截即可)
        public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
         HttpSession session = request.getSession();
            Object user = session.getAttribute("usersession");
            if(user == null) {
                response.sendRedirect("/login.html");
                return false;
            }
            return true;
    
        }
        @Override
        //后置拦截
        public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
            System.out.println("MyInterceptor.postHandle..");
        }
    
        @Override
        //最终拦截(视图渲染之后)
        public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
            System.out.println("MyInterceptor.afterCompletion..");
        }
    }

#### 方式二：继承适配器HandlerInterceptorAdapter（了解） ####

org.springframework.web.servlet.handler.HandlerInterceptorAdapter

public class MyInterceptor2 extends HandlerInterceptorAdapter {
    
        @Override
        public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
            System.out.println("MyInterceptor2.preHandle");
            return super.preHandle(request, response, handler);
        }
    
        @Override
        public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
            System.out.println("MyInterceptor2.postHandle");
            super.postHandle(request, response, handler, modelAndView);
        }
    
        @Override
        public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
            System.out.println("MyInterceptor2.afterCompletion");
            super.afterCompletion(request, response, handler, ex);
        }
    }

### 2.2 在SpringMVC配置文件中配置拦截器 ###

**功能：用于配置拦截哪些资源**

<mvc:interceptors>
            <mvc:interceptor>
                
                <mvc:mapping path="/**"/>
                
                
                <mvc:exclude-mapping path="/logincheck"/>   
                <mvc:exclude-mapping path="/login.html"/>   
                <mvc:exclude-mapping path="/static/**"/>  
    
                
                <bean class="com.project.Spring02.lanjieqi.MyInterceptor"/>
            </mvc:interceptor>
    
        </mvc:interceptors>

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc4NDY3Mw_size_16_color_FFFFFF_t_70 1]

# 3、小结 #

1.定义拦截器有两种方式,可以实现HandlerInterceptor接口,也可以实现HandlerInterceptorAdapter类.  
2.**拦截器只能在访问controller 的方法时进行拦截（只能拦截请求）.**  
3.拦截器可以在访问controller的方法前,访问controller方法之后,和视图渲染完成之后三个时机进行功能的增强.  
4./*和/\*\*的区别  
/*:只能匹配一级路径  
/\*\*:匹配多级路径

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc4NDY3Mw_size_16_color_FFFFFF_t_70]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/18/5e7e448ba40e455e8343099328c2080e.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc4NDY3Mw_size_16_color_FFFFFF_t_70 1]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/18/40d4ba363314416cbbe3a3940bdbf31d.png