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下面步骤中主要讲解如何实现文件上传,关于SSM的详细配置见

项目的相关结构如下

1）导入相应的maven依赖

<properties>    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>    <maven.compiler.source>1.7</maven.compiler.source>    <maven.compiler.target>1.7</maven.compiler.target>    <spring.version>4.3.7.RELEASE</spring.version>  </properties>  <dependencies>    <dependency>      <groupId>junit</groupId>      <artifactId>junit</artifactId>      <version>4.11</version>      <scope>test</scope>    </dependency>    <!-- 1.日志 -->    <!-- 实现slf4j接口并整合 -->    <dependency>      <groupId>ch.qos.logback</groupId>      <artifactId>logback-classic</artifactId>      <version>1.2.1</version>    </dependency>    <!-- 3.Servlet web -->    <dependency>      <groupId>taglibs</groupId>      <artifactId>standard</artifactId>      <version>1.1.2</version>    </dependency>    <dependency>      <groupId>jstl</groupId>      <artifactId>jstl</artifactId>      <version>1.2</version>    </dependency>    <dependency>      <groupId>com.fasterxml.jackson.core</groupId>      <artifactId>jackson-databind</artifactId>      <version>2.8.7</version>    </dependency>    <dependency>      <groupId>javax.servlet</groupId>      <artifactId>javax.servlet-api</artifactId>      <version>3.1.0</version>    </dependency>    <!-- 4.Spring -->    <!-- 1)Spring核心 -->    <dependency>      <groupId>org.springframework</groupId>      <artifactId>spring-core</artifactId>      <version>${
   spring.version}</version>    </dependency>    <dependency>      <groupId>org.springframework</groupId>      <artifactId>spring-beans</artifactId>      <version>${
   spring.version}</version>    </dependency>    <dependency>      <groupId>org.springframework</groupId>      <artifactId>spring-context</artifactId>      <version>${
   spring.version}</version>    </dependency>    <!-- 2)Spring DAO层 -->    <dependency>      <groupId>org.springframework</groupId>      <artifactId>spring-jdbc</artifactId>      <version>${
   spring.version}</version>    </dependency>    <dependency>      <groupId>org.springframework</groupId>      <artifactId>spring-tx</artifactId>      <version>${
   spring.version}</version>    </dependency>    <!-- 3)Spring web -->    <dependency>      <groupId>org.springframework</groupId>      <artifactId>spring-web</artifactId>      <version>${
   spring.version}</version>    </dependency>    <dependency>      <groupId>org.springframework</groupId>      <artifactId>spring-webmvc</artifactId>      <version>${
   spring.version}</version>    </dependency>    <!-- 4)Spring test -->    <dependency>      <groupId>org.springframework</groupId>      <artifactId>spring-test</artifactId>      <version>${
   spring.version}</version>    </dependency>    <!-- Map工具类 -->    <dependency>      <groupId>commons-collections</groupId>      <artifactId>commons-collections</artifactId>      <version>3.2</version>    </dependency>    <!-- https://mvnrepository.com/artifact/commons-fileupload/commons-fileupload -->    <dependency>      <groupId>commons-fileupload</groupId>      <artifactId>commons-fileupload</artifactId>      <version>1.3.2</version>    </dependency>  </dependencies>

2）SpringMvc的相关配置

spring-web.xml

<?xml version="1.0" encoding="UTF-8"?><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-3.2.xsd">    <!--开启SpringMvc注解模式-->    <mvc:annotation-driven/>    <!--静态资源默认servlet配置    (1)加入对静态资源的处理:js,gif,png    (2)允许使用"/"做整体映射-->    <mvc:resources mapping="/resources/**" location="/resources/"/>    <mvc:default-servlet-handler/>    <!--定义视图解析器-->    <bean id="viewResolver"          class="org.springframework.web.servlet.view.InternalResourceViewResolver">        <property name="prefix" value="/WEB-INF/html/"></property>        <property name="suffix" value=".html"></property>    </bean>    <!--文件上传解析器-->    <bean id="multipartResolver"          class="org.springframework.web.multipart.commons.CommonsMultipartResolver">        <property name="defaultEncoding" value="utf-8"></property>        <property name="maxUploadSize" value="10485760000"></property><!-- 最大上传文件大小 -->        <property name="maxInMemorySize" value="10960"></property>    </bean>    <!-- 在spring-mvc.xml文件中加入这段配置后，spring返回给页面的都是utf-8编码了 -->    <bean            class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">        <property name="messageConverters">            <list>                <bean                        class="org.springframework.http.converter.StringHttpMessageConverter">                    <property name="supportedMediaTypes">                        <list>                            <value>text/html;charset=UTF-8</value>                        </list>                    </property>                </bean>            </list>        </property>    </bean>    <!-- 4.扫描web相关的bean(相关的Controller类) -->    <context:component-scan base-package="com.sakura.web" /></beans>

web.xml

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee                      http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"         version="3.1" metadata-complete="true">  <display-name>Archetype Created Web Application</display-name>  <servlet>    <servlet-name>spring-dispatcher</servlet-name>    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>    <init-param>      <param-name>contextConfigLocation</param-name>      <param-value>classpath:spring/spring-*.xml</param-value>    </init-param>  </servlet>  <servlet-mapping>    <servlet-name>spring-dispatcher</servlet-name>    <!--默认匹配所有的请求-->    <url-pattern>/</url-pattern>  </servlet-mapping></web-app>

3）前台页面upload.html和download.html

upload.html

<!DOCTYPE html><html lang="en"><head>    <meta charset="UTF-8">    <title>文件上传</title></head><body><span id="warn" style="color: red"></span><br><input type="file" id="file"><br><input type="button" id="submit" value="上传"></body><script type="text/javascript" src="../resources/js/jquery-3.3.1.min.js"></script><script>    $(function () {
           var url = "/file/upload";        $('#submit').click(function () {
               //获取上传的文件流            var file = $('#file')[0].files[0];            if (file==''||!file){
                   $('#warn').text('请选择文件');            } else {
                   var formData = new FormData();                formData.append("file",file);                $.ajax({
                       url:url,                    type:'POST',                    data:formData,                    contentType:false,                    processData:false,                    success:function (data) {
                           if (data.success){
                               $('#warn').text('');                            alert(data.errMsg);                        } else {
                               $('#warn').text(data.errMsg);                        }                    }                })            }        })    })</script></html>

download.html

<!DOCTYPE html><html lang="en"><head>    <meta charset="UTF-8">    <title>Title</title></head><body><a href="/file/download?fileName=file.txt">file.txt</a></body></html>

4)后台Controller层中的FrontendController.java和FileUploadController.java

FrontendController.java

@Controller@RequestMapping("/frontend")public class FrontendController {
       /**     * 文件上传页面     * @return     */    @RequestMapping(value = "/upload",method = RequestMethod.GET)    public String FileUpload(){
           return "file/upload";    }    /**     * 文件下载页面     * @return     */    @RequestMapping(value = "/download",method = RequestMethod.GET)    public String FikeDownload(){
           return "file/download";    }}

FileUploadController.java

@Controller@RequestMapping("/file")public class FileUploadController {
       /**     * 文件上传     */    @ResponseBody    @RequestMapping(value = "/upload",method = RequestMethod.POST)    public HashMap<String,Object> fileUpload(HttpServletRequest request){
           HashMap<String,Object> modelMap = new HashMap<>();        //获取文件输入流        MultipartHttpServletRequest multipartHttpServletRequest = null;        CommonsMultipartFile file = null;        CommonsMultipartResolver resolver = new CommonsMultipartResolver(request.getSession().getServletContext());        //判断是否上传了文件        if (resolver.isMultipart(request)){
               multipartHttpServletRequest = (MultipartHttpServletRequest) request;            file = (CommonsMultipartFile) multipartHttpServletRequest.getFile("file");            //获取上传文件的原始名称            String originalFilename = file.getOriginalFilename();            //设置上传文件的保存地址目录(这里我设置在本地D盘中)            System.out.println("request.getServletContext().getRealPath(\"/upload\"):"+request.getServletContext().getRealPath("/upload"));            String dirPath = "d:/Sakura/upload/";            //如果保存文件的地址不存在,就先创建目录            File filePath = new File(dirPath);            if (!filePath.exists()){
                   filePath.mkdirs();            }            //使用UUID从命名上传的文件名称            String newFilename = UUID.randomUUID() + "_" + originalFilename;            try {
                   //使用CommonsMultipartFile完成文件上传到指定位置                file.transferTo(new File(dirPath+newFilename));            } catch (IOException e) {
                   modelMap.put("success",false);                modelMap.put("errMsg",e.getMessage());                return modelMap;            }            modelMap.put("success",true);            modelMap.put("errMsg","文件上传成功");        }else {
               modelMap.put("success",false);            modelMap.put("errMsg","未上传文件");        }        return modelMap;    }    @RequestMapping(value = "/download",method = RequestMethod.GET)    public ResponseEntity<byte[]> fileDownload(HttpServletRequest request, HttpServletResponse response,String fileName) throws Exception {
           //若传入的文件名有中文等非英文字符则直接报错：由于被认为是客户端对错误（例如：畸形的请求语法、无效的请求信息帧或者虚拟的请求路由），服务器无法或不会处理当前请求。        //所以，要假定在浏览器发出的下载请求(就是由用户点击超链接而引起)，传入的fileName参数的值不能含中文等字符。        System.out.println(fileName);        //这里下载的文件在我电脑中的D:/Sakura/upload/file.txt中        String dirPath = "D:"+File.separator+"Sakura"+File.separator+"upload";        //创建该文件对象        File file = new File(dirPath+File.separator+fileName);        System.out.println(file.toString()+" "+file.exists());        if (!file.exists()){
               request.setAttribute("theMessage", "<script>alert('文件已不存在！');</script>");            request.getRequestDispatcher("download.jsp").forward(request, response);            return null;        } else {
               // 对文件名编码，防止中文文件乱码            fileName = this.getFilename(request, fileName);            // 设置响应头            HttpHeaders headers = new HttpHeaders();            // 通知浏览器以下载的方式打开文件            headers.setContentDispositionFormData("attachment", fileName);            // 定义以流的形式下载返回文件数据            headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);            // 使用Spring MVC框架的ResponseEntity对象封装返回下载数据            return new ResponseEntity<byte[]>(FileUtils.readFileToByteArray(file), headers, HttpStatus.OK); // HttpStatus.OK 是200        }    }    /**     * 根据浏览器的不同进行编码设置，返回编码后的文件名     */    public String getFilename(HttpServletRequest request, String fileName) throws Exception {
           // IE不同版本User-Agent中出现的关键词        String[] IEBrowserKeyWords = {
   "MSIE", "Trident", "Edge"};        // 获取请求头代理信息        String userAgent = request.getHeader("User-Agent");        for (String keyWord : IEBrowserKeyWords) {
               if (userAgent.contains(keyWord)) {
                   //IE内核浏览器，统一为UTF-8编码显示                return URLEncoder.encode(fileName, "UTF-8");            }        }        //火狐等其它浏览器统一为ISO-8859-1编码显示        return new String(fileName.getBytes("UTF-8"), "ISO-8859-1");    }}

运行效果(开启Tomcat)

文件上传

文件下载