18 SpringMVC 文件上传和异常处理

2022-10-05 20:30:26

1.文件上传的必要前提

(1)form 表单的 enctype 取值必须是：multipart/form-data
(默认值是:application/x-www-form-urlencoded) enctype:是表单请求正文的类型
(2)method 属性取值必须是 Post
(3)提供一个文件选择域<input type=”file” />

2.文件上传环境搭建

(1)项目结构

(2)部分重要代码

<1>web.xml

<!DOCTYPE web-app PUBLIC

 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"

 "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>

  <display-name>Archetype Created Web Application</display-name>

  <!--配置前端控制器，让前端控制器去加载resources包下的springmvc.xml配置文件-->

  <servlet>

    <servlet-name>dispatcherServlet</servlet-name>

    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>

    <!--全局的初始化参数-->

    <init-param>

      <param-name>contextConfigLocation</param-name>

      <param-value>classpath:springmvc.xml</param-value>

    </init-param>

  </servlet>

  <servlet-mapping>

    <servlet-name>dispatcherServlet</servlet-name>

    <url-pattern>/</url-pattern>

  </servlet-mapping>

  <!--配置解决中文乱码的过滤器-->

  <filter>

    <filter-name>characterEncodingFilter</filter-name>

    <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>

    <init-param>

      <param-name>encoding</param-name>

      <param-value>UTF-8</param-value>

    </init-param>

  </filter>

  <filter-mapping>

    <filter-name>characterEncodingFilter</filter-name>

    <url-pattern>/*</url-pattern>

  </filter-mapping>

</web-app>

<2>spirngmvc.xml

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

       xmlns:mvc="http://www.springframework.org/schema/mvc"

       xmlns:context="http://www.springframework.org/schema/context"

       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

       xsi:schemaLocation="

        http://www.springframework.org/schema/beans

        http://www.springframework.org/schema/beans/spring-beans.xsd

        http://www.springframework.org/schema/mvc

        http://www.springframework.org/schema/mvc/spring-mvc.xsd

        http://www.springframework.org/schema/context

        http://www.springframework.org/schema/context/spring-context.xsd">

    <!-- 开启注解扫描 -->

    <context:component-scan base-package="lucky"/>

    <!-- 视图解析器对象 -->

    <bean id="internalResourceViewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">

        <!--配置控制器方法中return返回的字符串对应的同名文件所在目录-->

        <property name="prefix" value="/WEB-INF/pages/"/>

        <!--配置文件的后缀名-->

        <property name="suffix" value=".jsp"/>

    </bean>

    <!-- 开启SpringMVC框架注解的支持 -->

    <mvc:annotation-driven/>

</beans>

<3>index.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<html>

<head>

    <title>Title</title>

</head>

<body>

    <h3>文件上传</h3>

    <form action="/day19_fileupload/user/fileUploadTest01" method="post" enctype="multipart/form-data">

        选择文件：<input type="file" name="upload"><br>

        <input type="submit" value="上传">

    </form>

</body>

</html>

3.传统方式上传文件

package lucky.controller;

import org.apache.commons.fileupload.FileItem;

import org.apache.commons.fileupload.disk.DiskFileItemFactory;

import org.apache.commons.fileupload.servlet.ServletFileUpload;

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.RequestMapping;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.io.File;

import java.util.List;

import java.util.UUID;

@Controller

@RequestMapping(path = "/user")

public class UserController {

    //传统方式上传文件

    @RequestMapping(path = "/fileUploadTest01")

    public String fileUploadTest01(HttpServletRequest request, HttpServletResponse response) throws Exception{

        System.out.println("文件上传");

        // 使用fileupload组件完成文件上传

        // 上传的位置

        String path = request.getSession().getServletContext().getRealPath("/uploads/");

        System.out.println(path);  //查看文件上传的路径

        // 判断，该路径是否存在

        File file = new File(path);

        if(!file.exists()){

            // 创建该文件夹

            file.mkdirs();

        }

        // 解析request对象，获取上传文件项

        DiskFileItemFactory factory = new DiskFileItemFactory();

        ServletFileUpload upload = new ServletFileUpload(factory);

        // 解析request

        List<FileItem> items = upload.parseRequest(request);

        // 遍历

        for(FileItem item:items){

            // 进行判断，当前item对象是否是上传文件项

            if(item.isFormField()){

                // 说明普通表单向

            }else{

                // 说明上传文件项

                // 获取上传文件的名称

                String filename = item.getName();

                // 把文件的名称设置唯一值，uuid

                String uuid = UUID.randomUUID().toString().replace("-", "");

                filename = uuid+"_"+filename;

                // 完成文件上传

                item.write(new File(path,filename));

                // 删除临时文件

                item.delete();

            }

        }

        return "success";

    }

}

4.Springmvc方式文件上传

原理分析图：

package lucky.controller;

import org.apache.commons.fileupload.FileItem;

import org.apache.commons.fileupload.disk.DiskFileItemFactory;

import org.apache.commons.fileupload.servlet.ServletFileUpload;

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.multipart.MultipartFile;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.io.File;

import java.util.List;

import java.util.UUID;

@Controller

@RequestMapping(path = "/user")

public class UserController {

    /**

     * springmvc方式上传文件

     * 注意：请求参数MultipartFile upload 的名称upload必须与index.jsp中input标签的属性名一致，否则会造成空指针异常

     * @return

     */

    @RequestMapping(path = "/fileUploadTest02")

    public String fileUploadTest02(HttpServletRequest request, MultipartFile upload) throws Exception{

        System.out.println("springmvc文件上传");

        // 使用fileupload组件完成文件上传

        // 上传的位置

        String path = request.getSession().getServletContext().getRealPath("/uploads/");

        System.out.println(path);  //查看文件上传的路径

        // 判断，该路径是否存在

        File file = new File(path);

        if(!file.exists()){

            // 创建该文件夹

            file.mkdirs();

        }

        // 说明上传文件项

        // 获取上传文件的名称

        String filename = upload.getOriginalFilename();

        // 把文件的名称设置唯一值，uuid

        String uuid = UUID.randomUUID().toString().replace("-", "");

        filename = uuid+"_"+filename;

        // 完成文件上传

        upload.transferTo(new File(path,filename));

        return "success";

    }

}

5.Springmvc异常处理

原理分析图：

(1)项目结构

(2)部分重要代码

<1>控制器类：UserController.java

package lucky.controller;

import lucky.exception.CustomException;

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.RequestMapping;

@Controller

@RequestMapping(path = "/user")

public class UserController {

    @RequestMapping(path = "/testException")

    public String testException() throws CustomException {

        System.out.println("testException执行了");

        try {

            //模拟异常

            int a=10/0;

        } catch (Exception e) {

            //抛出自定义异常

            throw new CustomException("被除数有问题");

        }

        return "success";

    }

}

<2>自定义异常类

package lucky.exception;

/**

 * 自定义异常类

 */

public class CustomException extends Exception{

    //存储提示信息

    private String message;

    public String getMessage() {

        return message;

    }

    public void setMessage(String message) {

        this.message = message;

    }

    public CustomException(String message) {

        this.message = message;

    }

}

<3>异常处理器：CustomExceptionResolver.java

package lucky.exception;

import org.springframework.web.servlet.HandlerExceptionResolver;

import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 * 异常处理器

 */

public class CustomExceptionResolver implements HandlerExceptionResolver {

    /**

     *处理异常的业务逻辑

     */

    @Override

    public ModelAndView resolveException(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) {

        //获取异常对象

        CustomException customException=null;

        if(e instanceof CustomException){

            customException= (CustomException) e;

        }else {

            customException=new CustomException("系统正在维护。。。");

        }

        //创建ModelAndView

        ModelAndView mv=new ModelAndView();

        mv.addObject("errormsg",e.getMessage());

        mv.setViewName("error");

        return mv;

    }

}

<4>springmvc.xml文件中配置异常处理器

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

       xmlns:mvc="http://www.springframework.org/schema/mvc"

       xmlns:context="http://www.springframework.org/schema/context"

       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

       xsi:schemaLocation="

        http://www.springframework.org/schema/beans

        http://www.springframework.org/schema/beans/spring-beans.xsd

        http://www.springframework.org/schema/mvc

        http://www.springframework.org/schema/mvc/spring-mvc.xsd

        http://www.springframework.org/schema/context

        http://www.springframework.org/schema/context/spring-context.xsd">

    <!-- 开启注解扫描 -->

    <context:component-scan base-package="lucky"/>

    <!-- 视图解析器对象 -->

    <bean id="internalResourceViewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">

        <!--配置控制器方法中return返回的字符串对应的同名文件所在目录-->

        <property name="prefix" value="/WEB-INF/pages/"/>

        <!--配置文件的后缀名-->

        <property name="suffix" value=".jsp"/>

    </bean>

    <!--配置异常处理器-->

    <bean id="customExceptionResolver" class="lucky.exception.CustomExceptionResolver"/>

    <!-- 开启SpringMVC框架注解的支持 -->

    <mvc:annotation-driven/>

</beans>

<6>相关jsp页面

index.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<html>

<head>

    <title>Title</title>

</head>

<body>

    <h3>异常处理</h3>

    <a href="/day19_exception/user/testException">异常处理</a>

</body>

</html>

error.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>

<html>

<head>

    <title>Title</title>

</head>

<body>

    <h3>error.jsp</h3>

    ${errormsg}

</body>

</html>

(3)执行效果图

码农公寓

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