SpringMVC - 拦截器和异常处理机制

梦里梦外; 2023-10-10 11:45 60阅读 0赞

#### SpringMVC拦截器 ####

类似于Servlet开发中的过滤器Filter，用于对处理器进行预处理和后处理。(责任链模式，AOP思想)

1.创建拦截器实现HandlerInterceptor接口

public class MyInterceptor1 implements HandlerInterceptor {
        
        //在目标方法执行之前 执行
        public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        
            System.out.println("preHandle...");
            return true; /*返回值 false:后面方法都不执行 true:后面方法都执行*/
        }
    
        //在目标方法执行之后 视图对象返回之前执行
        public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        
            System.out.println("postHandle...");
        }
    
        //整个流程都执行完毕后 执行
        public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        
            System.out.println("afterCompletion...");
        }
    }

2.在`spring-mvc.xml`中配置拦截器

<mvc:interceptors>
        <mvc:interceptor>
            
            <mvc:mapping path="/**"/>
            <bean class="com.heiko.interceptor.MyInterceptor1"/>
        </mvc:interceptor>
    </mvc:interceptors>

3.测试拦截器的拦截效果  
执行`http://localhost:8080/my_spring_interceptor_war_exploded//target`

@RequestMapping("/target")
    public ModelAndView show() {
        
        System.out.println("目标资源执行....");
        ModelAndView modelAndView = new ModelAndView();
        modelAndView.addObject("name", "heiko");
        modelAndView.setViewName("index");
        return modelAndView;
    }

可以看到打印了日志

preHandle...
    目标资源执行....
    postHandle...
    afterCompletion...

有了拦截器，我们就可以在preHandler中进行拦截跳转操作

public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        
        System.out.println("preHandle...");
        String params = request.getParameter("params");
        if (params.equals("yes")) {
        
            return true;
        } else {
        
            request.getRequestDispatcher("/error.jsp").forward(request, response);
            return false;
        }

在postHandle中，可以进行参数的增加修改

public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        
        System.out.println("postHandle...");
        modelAndView.addObject("name", "zhangsan");
    }

##### 多个拦截器 #####

多个拦截器，会先顺序执行preHandle，再反顺序调用postHandle和afterCompletion。

preHandle1...
    preHandle2...
    目标资源执行...
    postHandle2...
    postHandle1...
    afterCompletion2...
    afterCompletion1...

#### SpringMVC异常处理机制 ####

可以用来进行统一的异常处理。  
新建处理类继承自HandlerExceptionResolver

public class MyExceptionResolver implements HandlerExceptionResolver {
        
        /*
        参数Exception：异常对象
        返回值ModelAndView：跳转到错误视图信息
     */
        public ModelAndView resolveException(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) {
        
            ModelAndView modelAndView = new ModelAndView();
    
            if(e instanceof MyException){
        
                modelAndView.addObject("info","自定义异常");
            }else if(e instanceof ClassCastException){
        
                modelAndView.addObject("info","类转换异常");
            }
    
            modelAndView.setViewName("error");
    
            return modelAndView;
        }
    }

在`spring-mvc.xml`中配置自定义异常处理器

如果出现Crash，就可以进行统一处理了。

### 其他 ###

> 文中代码:详见[https://github.com/EthanCo/SpringTest][https_github.com_EthanCo_SpringTest]

[https_github.com_EthanCo_SpringTest]: https://github.com/EthanCo/SpringTest