java架构之路-（SpringMVC篇）SpringMVC主要流程源码解析（下）注解配置，统一错误处理和拦截器

　　我们上次大致说完了执行流程，也只是说了大致的过程，还有中间会出错的情况我们来处理一下。

统一异常处理

比如我们的运行时异常的500错误。我们来自定义一个类

package com.springmvcbk.utils;

import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.ByteArrayOutputStream;
import java.io.PrintStream;

public class MyExceptionResolver implements HandlerExceptionResolver {

    public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {
        ModelAndView mv = new ModelAndView();
        mv.setViewName("/WEB-INF/page/error.jsp");
        if (ex instanceof IllegalAccessException){
            mv.addObject("erroeType","非法参数");
        }else{
            mv.addObject("erroeType",ex.getClass().getSimpleName());
        }
        mv.addObject("message",ex.getMessage());
        ByteArrayOutputStream bo = new ByteArrayOutputStream();
        ex.printStackTrace(new PrintStream(bo,true));
        mv.addObject("stack",bo.toString());
        return mv;
    }
}

将我们的类注入到我们的spring-mvc.xml内

<bean class="com.springmvcbk.utils.MyExceptionResolver"/>

我们让我们的代码运行时异常就可以跳转到我们的error页面上去了。

拦截器

　　还有我们常用的拦截器，也就是我们拿到的HandlerInterceptor来处理拦截的。

package com.springmvcbk.utils;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class MyInterceptor implements HandlerInterceptor {

    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandle");
        return true;
    }

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

    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion");
    }
}

<mvc:interceptors>
    <mvc:interceptor>
        <mvc:mapping path="/**"/>
        <bean class="com.springmvcbk.utils.MyInterceptor"/>
    </mvc:interceptor>
</mvc:interceptors>

配置我们的拦截范围也就可以了。如果执行过程出现错误就不会执行postHandle了。

还有最后一项，我们最熟悉的@RequestMapping注解的形式，我们还是先来一个最精简的启动

package com.springmvcbk.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@Controller
public class SpringmvController {

    @RequestMapping(value = "zhangsan")
    public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {
        ModelAndView modelAndView = new ModelAndView();
        modelAndView.setViewName("/WEB-INF/page/index.jsp");
        modelAndView.addObject("name","张三");
        return modelAndView;
    }
}

<?xml version="1.0" encoding="GBK"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context
       http://www.springframework.org/schema/context/spring-context.xsd
       http://www.springframework.org/schema/mvc
       http://www.springframework.org/schema/mvc/spring-mvc.xsd">

    <context:component-scan base-package="com.springmvcbk.controller"/>
    <mvc:annotation-driven/>
</beans>

还有我们上次忘记的一个配置，每次返回都要写全路径，累死了，我们在spring-mvc.xml加入这样的配置

 <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
 　　<property name="prefix" value="WEB-INF/page/"/>
 　　<property name="suffix" value=".jsp"/>
    <property name="viewClass" value="org.springframework.web.servlet.view.InternalResourceView"/>
</bean>

加入这样的配置就可以了，完事，配置就是这样的简单，和配置文件不同的是加入一个扫描器就可以了。与上次的流程几乎是一致的，映射器和适配器有一点点的差异。

今天我们就说到这里了， 关于SpringMVC后面我会尽快给出一个完整的面试题。

最进弄了一个公众号，小菜技术，欢迎大家的加入