SSM框架-SpringMVC 实例文件上传下载

一、新建一个Web工程，导入相关的包

springmvc的包+commons-fileupload.jar+connom-io.jar+commons-logging,jar+jstl.jar+standard.jar

整个相关的包如下：

整个工程目录如下：

二、配置web.xml和SpringMVC文件

（1）web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    id="WebApp_ID" version="3.0">
    <!-- SpringMVC的前端控制器 -->
    <servlet>
        <servlet-name>MyDispatcher</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <!-- 设置自己定义的控制器xml文件 -->
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>/WEB-INF/springMVC-servlet.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <!-- Spring MVC配置文件结束 -->

    <!-- 拦截设置 -->
    <servlet-mapping>
        <servlet-name>MyDispatcher</servlet-name>
        <!-- 由SpringMVC拦截所有请求 -->
        <url-pattern>/</url-pattern>
    </servlet-mapping>

</web-app>

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    id="WebApp_ID" version="3.0">
    <!-- SpringMVC的前端控制器 -->
    <servlet>
        <servlet-name>MyDispatcher</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <!-- 设置自己定义的控制器xml文件 -->
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>/WEB-INF/springMVC-servlet.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <!-- Spring MVC配置文件结束 -->

    <!-- 拦截设置 -->
    <servlet-mapping>
        <servlet-name>MyDispatcher</servlet-name>
        <!-- 由SpringMVC拦截所有请求 -->
        <url-pattern>/</url-pattern>
    </servlet-mapping>

</web-app>

(2)springMVC-servlet.xml文件

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:util="http://www.springframework.org/schema/util"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"
     xmlns:mvc="http://www.springframework.org/schema/mvc"
    xsi:schemaLocation="
        http://www.springframework.org/schema/util
        http://www.springframework.org/schema/util/spring-util-3.0.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-3.0.xsd">

    <!-- 把标记了@Controller注解的类转换为bean -->
    <context:component-scan base-package="com.mucfc" />
    <!-- 对模型视图名称的解析，即在模型视图名称添加前后缀 -->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"
        p:prefix="/WEB-INF/views/" p:suffix=".jsp"/>

    <!-- 上传文件的设置 ，maxUploadSize=-1，表示无穷大。uploadTempDir为上传的临时目录 -->
   <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"
        p:defaultEncoding="UTF-8"
        p:maxUploadSize="5400000"
        p:uploadTempDir="fileUpload/temp"
     />

</beans>

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:util="http://www.springframework.org/schema/util"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"
     xmlns:mvc="http://www.springframework.org/schema/mvc"
    xsi:schemaLocation="
        http://www.springframework.org/schema/util
        http://www.springframework.org/schema/util/spring-util-3.0.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-3.0.xsd">

    <!-- 把标记了@Controller注解的类转换为bean -->
    <context:component-scan base-package="com.mucfc" />
    <!-- 对模型视图名称的解析，即在模型视图名称添加前后缀 -->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"
        p:prefix="/WEB-INF/views/" p:suffix=".jsp"/>

    <!-- 上传文件的设置 ，maxUploadSize=-1，表示无穷大。uploadTempDir为上传的临时目录 -->
   <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"
        p:defaultEncoding="UTF-8"
        p:maxUploadSize="5400000"
        p:uploadTempDir="fileUpload/temp"
     />

</beans>

三、单个文件上传

（1）控制器

@Controller
@RequestMapping("/file")
public class FileController {

    @RequestMapping("/toFile")
    public String toFileUpload() {
        return "fileUpload";
    }

    @RequestMapping("/toFile2")
    public String toFileUpload2() {
        return "fileUpload2";
    }

    /**
     * 方法一上传文件
     */
    @RequestMapping("/onefile")
    public String oneFileUpload(
            @RequestParam("file") CommonsMultipartFile file,
            HttpServletRequest request, ModelMap model) {

        // 获得原始文件名
        String fileName = file.getOriginalFilename();
        System.out.println("原始文件名:" + fileName);

        // 新文件名
        String newFileName = UUID.randomUUID() + fileName;

        // 获得项目的路径
        ServletContext sc = request.getSession().getServletContext();
        // 上传位置
        String path = sc.getRealPath("/img") + "/"; // 设定文件保存的目录

        File f = new File(path);
        if (!f.exists())
            f.mkdirs();
        if (!file.isEmpty()) {
            try {
                FileOutputStream fos = new FileOutputStream(path + newFileName);
                InputStream in = file.getInputStream();
                int b = 0;
                while ((b = in.read()) != -1) {
                    fos.write(b);
                }
                fos.close();
                in.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        System.out.println("上传图片到:" + path + newFileName);
        // 保存文件地址，用于JSP页面回显
        model.addAttribute("fileUrl", path + newFileName);
        return "fileUpload";
    }

    /**
     * 方法二上传文件，一次一张
     */
    @RequestMapping("/onefile2")
    public String oneFileUpload2(HttpServletRequest request,
            HttpServletResponse response) throws Exception {
        CommonsMultipartResolver cmr = new CommonsMultipartResolver(
                request.getServletContext());
        if (cmr.isMultipart(request)) {
            MultipartHttpServletRequest mRequest = (MultipartHttpServletRequest) (request);
            Iterator<String> files = mRequest.getFileNames();
            while (files.hasNext()) {
                MultipartFile mFile = mRequest.getFile(files.next());
                if (mFile != null) {
                    String fileName = UUID.randomUUID()
                            + mFile.getOriginalFilename();
                    String path = "d:/upload/" + fileName;

                    File localFile = new File(path);
                    mFile.transferTo(localFile);
                    request.setAttribute("fileUrl", path);
                }
            }
        }
        return "fileUpload";
    }
}

@Controller
@RequestMapping("/file")
public class FileController {

    @RequestMapping("/toFile")
    public String toFileUpload() {
        return "fileUpload";
    }

    @RequestMapping("/toFile2")
    public String toFileUpload2() {
        return "fileUpload2";
    }

    /**
     * 方法一上传文件
     */
    @RequestMapping("/onefile")
    public String oneFileUpload(
            @RequestParam("file") CommonsMultipartFile file,
            HttpServletRequest request, ModelMap model) {

        // 获得原始文件名
        String fileName = file.getOriginalFilename();
        System.out.println("原始文件名:" + fileName);

        // 新文件名
        String newFileName = UUID.randomUUID() + fileName;

        // 获得项目的路径
        ServletContext sc = request.getSession().getServletContext();
        // 上传位置
        String path = sc.getRealPath("/img") + "/"; // 设定文件保存的目录

        File f = new File(path);
        if (!f.exists())
            f.mkdirs();
        if (!file.isEmpty()) {
            try {
                FileOutputStream fos = new FileOutputStream(path + newFileName);
                InputStream in = file.getInputStream();
                int b = 0;
                while ((b = in.read()) != -1) {
                    fos.write(b);
                }
                fos.close();
                in.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        System.out.println("上传图片到:" + path + newFileName);
        // 保存文件地址，用于JSP页面回显
        model.addAttribute("fileUrl", path + newFileName);
        return "fileUpload";
    }

    /**
     * 方法二上传文件，一次一张
     */
    @RequestMapping("/onefile2")
    public String oneFileUpload2(HttpServletRequest request,
            HttpServletResponse response) throws Exception {
        CommonsMultipartResolver cmr = new CommonsMultipartResolver(
                request.getServletContext());
        if (cmr.isMultipart(request)) {
            MultipartHttpServletRequest mRequest = (MultipartHttpServletRequest) (request);
            Iterator<String> files = mRequest.getFileNames();
            while (files.hasNext()) {
                MultipartFile mFile = mRequest.getFile(files.next());
                if (mFile != null) {
                    String fileName = UUID.randomUUID()
                            + mFile.getOriginalFilename();
                    String path = "d:/upload/" + fileName;

                    File localFile = new File(path);
                    mFile.transferTo(localFile);
                    request.setAttribute("fileUrl", path);
                }
            }
        }
        return "fileUpload";
    }
}

（2）JSP,这个页面是用来上传又用来显示上传后的图片的页面fileUpload.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%>
<%
    String path = request.getContextPath();
    String basePath = request.getScheme() + "://"
            + request.getServerName() + ":" + request.getServerPort()
            + path + "/";
%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>用户上传图片页面</title>
 <base href="<%=basePath%>">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
    <center>
        <form action="file/onefile"
            method="post" enctype="multipart/form-data">
            <input type="file" name="file" />
            <input type="submit" value="上 传" />
        </form>
        <h5>上传结果：</h5>
        <img alt="暂无图片" src="${fileUrl}" />
    </center>
</body>
</html>

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%>
<%
    String path = request.getContextPath();
    String basePath = request.getScheme() + "://"
            + request.getServerName() + ":" + request.getServerPort()
            + path + "/";
%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>用户上传图片页面</title>
 <base href="<%=basePath%>">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
    <center>
        <form action="file/onefile"
            method="post" enctype="multipart/form-data">
            <input type="file" name="file" />
            <input type="submit" value="上 传" />
        </form>
        <h5>上传结果：</h5>
        <img alt="暂无图片" src="${fileUrl}" />
    </center>
</body>
</html>

现在运行后来看看效果，输入：http://localhost:8080/SpringMVCLearningChapter4_1/file/toFile

控制台输出结果，选择图片后

原始文件名:Chrysanthemum.jpg
上传图片到:E:workspace.metadata.pluginsorg.eclipse.wst.server.core mp0wtpwebappsSpringMVCLearningChapter4_1img/4eafc28c-4baa-4018-ac06-c4a5aec88d6cChrysanthemum.jpg

图片已被上传，可以在JSP中显示出来

来看看服务器的路径：E:workspace.metadata.pluginsorg.eclipse.wst.server.core mp0wtpwebappsSpringMVCLearningChapter4_1img

表明图片已经上传到服务器

方法二：

使用文件流的方式来上传

/**
 * 方法二上传文件，一次一张
 */
@RequestMapping("/onefile2")
public String oneFileUpload2(HttpServletRequest request,
        HttpServletResponse response) throws Exception {
    CommonsMultipartResolver cmr = new CommonsMultipartResolver(
            request.getServletContext());
    if (cmr.isMultipart(request)) {
        MultipartHttpServletRequest mRequest = (MultipartHttpServletRequest) (request);
        Iterator<String> files = mRequest.getFileNames();
        while (files.hasNext()) {
            MultipartFile mFile = mRequest.getFile(files.next());
            if (mFile != null) {
                String fileName = UUID.randomUUID()
                        + mFile.getOriginalFilename();
                String path = "d:/upload/" + fileName;

                File localFile = new File(path);
                mFile.transferTo(localFile);
                request.setAttribute("fileUrl", path);
            }
        }
    }
    return "fileUpload";
}

/**
 * 方法二上传文件，一次一张
 */
@RequestMapping("/onefile2")
public String oneFileUpload2(HttpServletRequest request,
        HttpServletResponse response) throws Exception {
    CommonsMultipartResolver cmr = new CommonsMultipartResolver(
            request.getServletContext());
    if (cmr.isMultipart(request)) {
        MultipartHttpServletRequest mRequest = (MultipartHttpServletRequest) (request);
        Iterator<String> files = mRequest.getFileNames();
        while (files.hasNext()) {
            MultipartFile mFile = mRequest.getFile(files.next());
            if (mFile != null) {
                String fileName = UUID.randomUUID()
                        + mFile.getOriginalFilename();
                String path = "d:/upload/" + fileName;

                File localFile = new File(path);
                mFile.transferTo(localFile);
                request.setAttribute("fileUrl", path);
            }
        }
    }
    return "fileUpload";
}

把

<center>
    <form action="file/onefile"
        method="post" enctype="multipart/form-data">
        <input type="file" name="file" />
        <input type="submit" value="上 传" />
    </form>
    <h5>上传结果：</h5>
    <img alt="暂无图片" src="${fileUrl}" />
</center>

<center>
    <form action="file/onefile"
        method="post" enctype="multipart/form-data">
        <input type="file" name="file" />
        <input type="submit" value="上 传" />
    </form>
    <h5>上传结果：</h5>
    <img alt="暂无图片" src="${fileUrl}" />
</center>

中的

<form action="file/onefile"

<form action="file/onefile"

改成

<form action="file/onefile2"

<form action="file/onefile2"

输入：http://localhost:8080/SpringMVCLearningChapter4_1/file/toFile

方法二指定上传到了本地E盘的upload文件夹

页面结果

四、多文件上传

（1）控制器

@RequestMapping("/toFile2")
public String toFileUpload2() {
    return "fileUpload2";
}

@RequestMapping("/toFile2")
public String toFileUpload2() {
    return "fileUpload2";
}

/**
 * 一次上传多张图片
 */
@RequestMapping("/threeFile")
public String threeFileUpload(
        @RequestParam("file") CommonsMultipartFile files[],
        HttpServletRequest request, ModelMap model) {

    List<String> list = new ArrayList<String>();
    // 获得项目的路径
    ServletContext sc = request.getSession().getServletContext();
    // 上传位置
    String path = sc.getRealPath("/img") + "/"; // 设定文件保存的目录
    File f = new File(path);
    if (!f.exists())
        f.mkdirs();

    for (int i = 0; i < files.length; i++) {
        // 获得原始文件名
        String fileName = files[i].getOriginalFilename();
        System.out.println("原始文件名:" + fileName);
        // 新文件名
        String newFileName = UUID.randomUUID() + fileName;
        if (!files[i].isEmpty()) {
            try {
                FileOutputStream fos = new FileOutputStream(path
                        + newFileName);
                InputStream in = files[i].getInputStream();
                int b = 0;
                while ((b = in.read()) != -1) {
                    fos.write(b);
                }
                fos.close();
                in.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        System.out.println("上传图片到:" + path + newFileName);
        list.add(path + newFileName);

    }
    // 保存文件地址，用于JSP页面回显
    model.addAttribute("fileList", list);
    return "fileUpload2";

}

/**
 * 一次上传多张图片
 */
@RequestMapping("/threeFile")
public String threeFileUpload(
        @RequestParam("file") CommonsMultipartFile files[],
        HttpServletRequest request, ModelMap model) {

    List<String> list = new ArrayList<String>();
    // 获得项目的路径
    ServletContext sc = request.getSession().getServletContext();
    // 上传位置
    String path = sc.getRealPath("/img") + "/"; // 设定文件保存的目录
    File f = new File(path);
    if (!f.exists())
        f.mkdirs();

    for (int i = 0; i < files.length; i++) {
        // 获得原始文件名
        String fileName = files[i].getOriginalFilename();
        System.out.println("原始文件名:" + fileName);
        // 新文件名
        String newFileName = UUID.randomUUID() + fileName;
        if (!files[i].isEmpty()) {
            try {
                FileOutputStream fos = new FileOutputStream(path
                        + newFileName);
                InputStream in = files[i].getInputStream();
                int b = 0;
                while ((b = in.read()) != -1) {
                    fos.write(b);
                }
                fos.close();
                in.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        System.out.println("上传图片到:" + path + newFileName);
        list.add(path + newFileName);

    }
    // 保存文件地址，用于JSP页面回显
    model.addAttribute("fileList", list);
    return "fileUpload2";

}

其实就是在单文件上传的方法一中来修改的，只不过弄成了个循环

（2）JSP显示页面fileUpload2.jsp

<%@ page language="java" import="java.util.*" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%
    String path = request.getContextPath();
    String basePath = request.getScheme() + "://"
            + request.getServerName() + ":" + request.getServerPort()
            + path + "/";
%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>用户上传图片页面</title>
<base href="<%=basePath%>">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
    <center>
        <form action="file/threeFile" method="post"
            enctype="multipart/form-data">
            <input type="file" name="file" /><br /> <input type="file"
                name="file" /><br /> <input type="file" name="file" /><br /> <input
                type="submit" value="上 传" />
        </form>
        <h5>上传结果：</h5>

        <c:forEach items="${fileList}" var="imagename">
                <img alt="暂无图片" src="${imagename}" /> <br/>
        </c:forEach>



    </center>
</body>
</html>

<%@ page language="java" import="java.util.*" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%
    String path = request.getContextPath();
    String basePath = request.getScheme() + "://"
            + request.getServerName() + ":" + request.getServerPort()
            + path + "/";
%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>用户上传图片页面</title>
<base href="<%=basePath%>">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
    <center>
        <form action="file/threeFile" method="post"
            enctype="multipart/form-data">
            <input type="file" name="file" /><br /> <input type="file"
                name="file" /><br /> <input type="file" name="file" /><br /> <input
                type="submit" value="上 传" />
        </form>
        <h5>上传结果：</h5>

        <c:forEach items="${fileList}" var="imagename">
                <img alt="暂无图片" src="${imagename}" /> <br/>
        </c:forEach>



    </center>
</body>
</html>

注意这里用了

</c:forEach>

</c:forEach>

表单，需要jstl.jar+standard.jar

（3）运行后输入：http://localhost:8080/SpringMVCLearningChapter4_1/file/toFile2（注意上面是单文件没有后面的数字2）

选择图片，然后点上传

控制台输出结果：

图片不清看文字 吧：

原始文件名:Desert.jpg
上传图片到:E:workspace.metadata.pluginsorg.eclipse.wst.server.core mp0wtpwebappsSpringMVCLearningChapter4_1img/2baccc77-43b6-4908-859d-507e86a04051Desert.jpg
原始文件名:Hydrangeas.jpg
上传图片到:E:workspace.metadata.pluginsorg.eclipse.wst.server.core mp0wtpwebappsSpringMVCLearningChapter4_1img/51ad04e0-82aa-4b2c-958d-f00651e9ed6bHydrangeas.jpg
原始文件名:Jellyfish.jpg
上传图片到:E:workspace.metadata.pluginsorg.eclipse.wst.server.core mp0wtpwebappsSpringMVCLearningChapter4_1img/dee340d8-9cc0-41ae-9959-f7fa47ff172bJellyfish.jpg

三张图片都可以显示出来了

来看看服务器，这就是刚刚上传的三张

五、上传文件列表显示

（1）控制器

/**
 * 列出所有的图片
 */
@RequestMapping("/listFile")
public String listFile(HttpServletRequest request,
        HttpServletResponse response) {
    // 获取上传文件的目录
    ServletContext sc = request.getSession().getServletContext();
    // 上传位置
    String uploadFilePath = sc.getRealPath("/img") + "/"; // 设定文件保存的目录
    // 存储要下载的文件名
    Map<String, String> fileNameMap = new HashMap<String, String>();
    // 递归遍历filepath目录下的所有文件和目录，将文件的文件名存储到map集合中
    listfile(new File(uploadFilePath), fileNameMap);// File既可以代表一个文件也可以代表一个目录
    // 将Map集合发送到listfile.jsp页面进行显示
    request.setAttribute("fileNameMap", fileNameMap);
    return "listFile";
}

/**
 * 列出所有的图片
 */
@RequestMapping("/listFile")
public String listFile(HttpServletRequest request,
        HttpServletResponse response) {
    // 获取上传文件的目录
    ServletContext sc = request.getSession().getServletContext();
    // 上传位置
    String uploadFilePath = sc.getRealPath("/img") + "/"; // 设定文件保存的目录
    // 存储要下载的文件名
    Map<String, String> fileNameMap = new HashMap<String, String>();
    // 递归遍历filepath目录下的所有文件和目录，将文件的文件名存储到map集合中
    listfile(new File(uploadFilePath), fileNameMap);// File既可以代表一个文件也可以代表一个目录
    // 将Map集合发送到listfile.jsp页面进行显示
    request.setAttribute("fileNameMap", fileNameMap);
    return "listFile";
}

（2）JSP文件listFile.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE HTML>
<html>
  <head>
    <title>下载文件显示页面</title>
  </head>

  <body>
      <!-- 遍历Map集合 -->
    <c:forEach var="me" items="${fileNameMap}">
        <c:url value="/file/downFile" var="downurl">
            <c:param name="filename" value="${me.key}"></c:param>
        </c:url>
        ${me.value}<a href="${downurl}">下载</a>
        <br/>
    </c:forEach>

  </body>
</html>

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE HTML>
<html>
  <head>
    <title>下载文件显示页面</title>
  </head>

  <body>
      <!-- 遍历Map集合 -->
    <c:forEach var="me" items="${fileNameMap}">
        <c:url value="/file/downFile" var="downurl">
            <c:param name="filename" value="${me.key}"></c:param>
        </c:url>
        ${me.value}<a href="${downurl}">下载</a>
        <br/>
    </c:forEach>

  </body>
</html>

（3）运行后输入：http://localhost:8080/SpringMVCLearningChapter4_1/file/listFile       

这些为刚刚上传到四张图片。

六、文件下载

（1）控制器

@RequestMapping("/downFile")
public void downFile(HttpServletRequest request,
        HttpServletResponse response) {
    System.out.println("1");
    // 得到要下载的文件名
    String fileName = request.getParameter("filename");
    System.out.println("2");
    try {
        fileName = new String(fileName.getBytes("iso8859-1"), "UTF-8");
        System.out.println("3");
        // 获取上传文件的目录
        ServletContext sc = request.getSession().getServletContext();
        System.out.println("4");
        // 上传位置
        String fileSaveRootPath = sc.getRealPath("/img");

        System.out.println(fileSaveRootPath + "\" + fileName);
        // 得到要下载的文件
        File file = new File(fileSaveRootPath + "\" + fileName);

        // 如果文件不存在
        if (!file.exists()) {
            request.setAttribute("message", "您要下载的资源已被删除！！");
            System.out.println("您要下载的资源已被删除！！");
            return;
        }
        // 处理文件名
        String realname = fileName.substring(fileName.indexOf("_") + 1);
        // 设置响应头，控制浏览器下载该文件
        response.setHeader("content-disposition", "attachment;filename="
                + URLEncoder.encode(realname, "UTF-8"));
        // 读取要下载的文件，保存到文件输入流
        FileInputStream in = new FileInputStream(fileSaveRootPath + "\" + fileName);
        // 创建输出流
        OutputStream out = response.getOutputStream();
        // 创建缓冲区
        byte buffer[] = new byte[1024];
        int len = 0;
        // 循环将输入流中的内容读取到缓冲区当中
        while ((len = in.read(buffer)) > 0) {
            // 输出缓冲区的内容到浏览器，实现文件下载
            out.write(buffer, 0, len);
        }
        // 关闭文件输入流
        in.close();
        // 关闭输出流
        out.close();
    } catch (Exception e) {

    }
}

@RequestMapping("/downFile")
public void downFile(HttpServletRequest request,
        HttpServletResponse response) {
    System.out.println("1");
    // 得到要下载的文件名
    String fileName = request.getParameter("filename");
    System.out.println("2");
    try {
        fileName = new String(fileName.getBytes("iso8859-1"), "UTF-8");
        System.out.println("3");
        // 获取上传文件的目录
        ServletContext sc = request.getSession().getServletContext();
        System.out.println("4");
        // 上传位置
        String fileSaveRootPath = sc.getRealPath("/img");

        System.out.println(fileSaveRootPath + "\" + fileName);
        // 得到要下载的文件
        File file = new File(fileSaveRootPath + "\" + fileName);

        // 如果文件不存在
        if (!file.exists()) {
            request.setAttribute("message", "您要下载的资源已被删除！！");
            System.out.println("您要下载的资源已被删除！！");
            return;
        }
        // 处理文件名
        String realname = fileName.substring(fileName.indexOf("_") + 1);
        // 设置响应头，控制浏览器下载该文件
        response.setHeader("content-disposition", "attachment;filename="
                + URLEncoder.encode(realname, "UTF-8"));
        // 读取要下载的文件，保存到文件输入流
        FileInputStream in = new FileInputStream(fileSaveRootPath + "\" + fileName);
        // 创建输出流
        OutputStream out = response.getOutputStream();
        // 创建缓冲区
        byte buffer[] = new byte[1024];
        int len = 0;
        // 循环将输入流中的内容读取到缓冲区当中
        while ((len = in.read(buffer)) > 0) {
            // 输出缓冲区的内容到浏览器，实现文件下载
            out.write(buffer, 0, len);
        }
        // 关闭文件输入流
        in.close();
        // 关闭输出流
        out.close();
    } catch (Exception e) {

    }
}

这里就是通过文件流的方式来下载图片的。

然后就可以自己选择下载的地方了。

终于讲完了，花了大半天啊！