SpringMVC-异常解析器和拦截器

￡神魔★判官ぃ 2022-10-14 15:57 156阅读 0赞

# 一.异常解析器，统一处理 #

Controller中的每个Handler不再自己处理异常，而是直接throws所有异常。

package com.cos.qf.common;
    
    import org.springframework.web.servlet.HandlerExceptionResolver;
    import org.springframework.web.servlet.ModelAndView;
    
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    
    /**
     * @author: qiuyongqi
     * @time: 15:01 2021/5/22
     * @description: 异常解析器：主体逻辑
     * 	             执行时刻：当handler中抛出异常时，会执行：捕获异常，并可以跳到错误页面
     */
    public class ExceptionRes implements HandlerExceptionResolver {
        
        public ModelAndView resolveException(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) {
            //创建一个ModelAndView
            ModelAndView modelAndView = new ModelAndView();
            System.out.println("异常解析器运行，处理全局问题");
            //识别异常
            if (e instanceof NullPointerException) {
                modelAndView.setViewName("redirect:/error.jsp");
            }else if (e instanceof NumberFormatException){
                modelAndView.setViewName("redirect:/error.jsp");
            }else {
                modelAndView.setViewName("redirect:/error.jsp");
            }
            return modelAndView;
        }
    }

<bean class="com.baizhi.exception.resolver.MyExResolver"></bean>

# 二.拦截器 #

## 1.定义拦截器 ##

执行顺序： preHandle--postHandle--afterCompletion

package com.cos.qf.web.interceptor;
    
    import com.cos.qf.entity.Emp;
    import com.cos.qf.servlet.impl.EmpServicesImpl;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.servlet.HandlerInterceptor;
    import org.springframework.web.servlet.ModelAndView;
    
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    
    public class MyInterceptor implements HandlerInterceptor {
    
        @Autowired
        private EmpServicesImpl empServices;
    
        /**
         * @author: qiuyongqi
         * @time: 11:12 2021/5/20
         * @description: 进入执行xcontroller方法之前的拦截方法
         */
        public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
            System.out.println("执行controller之前");
            HttpSession session = request.getSession();
            Emp login = (Emp) session.getAttribute("login");
            System.out.println(login);
            if (login!=null) {
                empServices.sayHi();
                return true;//放行，后续的拦截器或handler就会执行
            }
            response.sendRedirect("/error.jsp");
            return false;//中断请求
        }
    
        /**
         * @author: qiuyongqi
         * @time: 11:12 2021/5/20
         * @description: 执行完controller方法给出响应之前执行的拦截
         */
        public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
            System.out.println("执行controller方法后,的拦截");
        }
    
        /**
         * @author: qiuyongqi
         * @time: 11:13 2021/5/20
         * @description: 在view视图渲染数据结束后执行,资源回收
         */
        public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
            System.out.println("已经给视图渲染玩数据,在响应给用户前,回收资源");
        }
    }

## 2.配置拦截器 ##

<mvc:interceptors>
        <mvc:interceptor>
            <mvc:mapping path="/inter/test1"/>
            <mvc:mapping path="/inter/test2"/>
            <mvc:mapping path="/inter/test*"/> 
            <mvc:mapping path="/inter/**"/> 
            <mvc:exclude-mapping path="/inter/a/**"/>   
            <bean class="com.baizhi.interceptor.MyInter1"></bean>   
        </mvc:interceptor>
    </mvc:interceptors>