spring文件上传拦截器及异常处理

1文件上传

当enctype="multipart/form-data"时request.getParameter()方法失效

单文件上传
导入坐标

   <dependency>
            <groupId>commons-fileupload</groupId>
            <artifactId>commons-fileupload</artifactId>
            <version>1.3.1</version>
        </dependency>
        <dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.6</version>
        </dependency>

<form action="${pageContext.request.contextPath}/user/quick22" method="post" enctype="multipart/form-data">
    名称<input type="text" name="username"><br>
    文件<input type="file" name="uploadFile1"><br>
    文件<input type="file" name="uploadFile2"><br>
    文件<input type="submit" value="提交"><br>
</form>

配置文件上传解析器
在spring-mvc.xml中加入

   <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
       <!--上传文件编码类型-->
        <property name="defaultEncoding" value="UTF-8"></property>
       <!--单文件总大小-->
        <property name="maxUploadSize" value="500000"></property>
        <!--文件总大小-->
        <property name="maxUploadSizePerFile" value="1044000"></property>
    </bean>

这里上传到webapp下

@RequestMapping(value = "/quick22")
    @ResponseBody //不进行页面跳转不进行数据回写响应体为空
    public void save22(String username, MultipartFile uploadFile1, MultipartFile uploadFile2) throws IOException {
        System.out.println(username);
        //
        String originalFilename1 = uploadFile1.getOriginalFilename();
        String originalFilename2 = uploadFile2.getOriginalFilename();
        //获取servletContext对象
        WebApplicationContext webApplicationContext = ContextLoader.getCurrentWebApplicationContext();
        ServletContext servletContext = 
//获取真实路径
webApplicationContext.getServletContext();
        String realPath = servletContext.getRealPath("/");
        //上传到哪儿
        uploadFile1.transferTo(new File(realPath+originalFilename1));
        uploadFile2.transferTo(new File(realPath+originalFilename2));
    }

多文件上传
前台

<form action="${pageContext.request.contextPath}/user/quick23" method="post" enctype="multipart/form-data">
    名称<input type="text" name="username"><br>
    文件<input type="file" name="uploadFile"><br>
    文件<input type="file" name="uploadFile"><br>
    文件<input type="submit" value="提交"><br>
</form>

客户端用数组接循环存储就行

    @RequestMapping(value = "/quick23")
    @ResponseBody //不进行页面跳转不进行数据回写响应体为空
    public void save23(String username, MultipartFile[] uploadFile) throws IOException {
    
        System.out.println(username);
        WebApplicationContext webApplicationContext = ContextLoader.getCurrentWebApplicationContext();
        ServletContext servletContext = webApplicationContext.getServletContext();
        String realPath = servletContext.getRealPath("/");
        
        for (MultipartFile multipartFile : uploadFile) {
            String originalFilename = multipartFile.getOriginalFilename();
            multipartFile.transferTo(new File(realPath+originalFilename
            ));
        }
    }

2，springMVC拦截器
类似Servlet开发中的过滤器Filter 用于处理器的预处理和后处理
不会拦截js，css html jsp
1)创建MyInterceptorl一个类实现implements HandlerInterceptor
有三个方法

//在目标方法值前
  @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
 return flase;//放不放行
 }
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
      //再返回视图时执行
     }

//在返回视图后执行
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
}   

    <!--配置拦截器-->
    <mvc:interceptors>
        <mvc:interceptor>
            <!--对所有的目标方法都拦截-->
            <mvc:mapping path="/**"/>
            <bean class="com.flatly.interceptor.MyInterceptorl"/>
        </mvc:interceptor>
    </mvc:interceptors>

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

preHandle方法返回true才会执行目标方法
postHandle可以修改视图modelAndView

测试
携带参数param是yes放行index不然重定向error

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

在目标方法中存储name

    modelAndView.addObject("name","flatly");

返回试图前执行postHandle

        @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
      //再返回视图时执行
       modelAndView.addObject("name","flatlypostuppd");
        System.out.println("postHandle");
    }

在页面上取${name}为flatlypostuppd
配置多个拦截器
顺序（先过去再执行）
1preHandle 2preHandle 目标 postHandle2 postHandle1 afterCompletion2 afterCompletion1

3 异常处理机制
1spring提供简单异常处理机制SimpleMappingExceptionResolver
在spring-mvc.xml

   <!--配置异常处理器-->
    <bean class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
      <--这是默认的跳转页面视图-->
        <property name="defaultErrorView" value="error"/>
        <--异常类型与之匹配-->
        property name="exceptionMappings">
            <map>
                <entry key="java.lang.ClassCastException" value="error1"/>
                <entry key="com.itheima.exception.MyException" value="error2"/>
            </map>
        </property>
    </bean>

2自定义异常处理步骤
实现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;
    }
}

在前端取数据${info}

   <!--自定义异常处理器-->
    <bean class="com.itheima.resolver.MyExceptionResolver"/>