JavaWeb(九)：上传和下载

表单

进行文件上传时, 表单需要做的准备:

1). 请求方式为 POST: <form action="uploadServlet" method="post" ... >
2). 使用 file 的表单域: <input type="file" name="file"/>
3). 使用 multipart/form-data 的请求编码方式: <form action="uploadServlet" method="post" enctype="multipart/form-data">

<form action="uploadServlet" method="post" enctype="multipart/form-data">

    File: <input type="file" name="file"/>

    <input type="submit" value="Submit"/>

</form>

会自动生成一个输入框和一个按钮，输入框可供用户填写本地文件的文件名和路径名，按钮可以让浏览器打开一个文件选择框供用户选择文件：

4). 关于 enctype:

> application/x-www-form-urlencoded：表单 enctype 属性的默认值。这种编码方案使用有限的字符集，当使用了非字母和数字时，必须用”%HH”代替(H 代表十六进制数字)。对于大容量的二进制数据或包含非 ASCII 字符的文本来说，这种编码不能满足要求。

> multipart/form-data：form 设定了enctype=“multipart/form-data”属性后，表示表单以二进制传输数据

服务端

1). 不能再使用 request.getParameter() 等方式获取请求信息. 获取不到, 因为请求的编码方式已经改为 multipart/form-data, 以二进制的方式来提交请求信息，下面的Servlet请求不到

    <form action="uploadServlet" method="post" enctype="multipart/form-data">

        File: <input type="file" name="file" />

        <br>

        <br>

        Desc: <input type="text" name="desc" />

        <br>

        <br>

        <input type="submit" value="Submit" />

    </form>

Servlet

public class UploadServlet extends HttpServlet{

    private static final long serialVersionUID = 1L;

    @Override

    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        // 1. 获取请求信息

        String file = req.getParameter("file");

    }

}

2). 可以使用输入流的方式来获取. 但不建议这样做

package com.aidata.web;

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.io.Reader;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class UploadServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    @Override

    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        InputStream in = req.getInputStream();

        Reader reader = new InputStreamReader(in);

        BufferedReader bufferedReader = new BufferedReader(reader);

        String str = null;

        while ((str = bufferedReader.readLine()) != null) {

            System.out.println(str);

        }

    }

}

使用 commons-fileupload 组件

具体使用 commons-fileupload 组件来完成文件的上传操作

搭建环境

加入 jar包
commons-fileupload-1.2.1.jar
commons-io-2.0.jar

基本思想:

> commons-fileupload 可以解析请求，得到一个 FileItem 对象组成的 List
> commons-fileupload 把所有的请求信息都解析为 FileItem 对象，无论是一个一般的文本域还是一个文件域
> 可以调用 FileItem 的 isFormField() 方法来判断是一个表单域或不是表单域(即是一个文件域)
> 再来进一步获取信息
表单域

if (item.isFormField()) {

    String name = item.getFieldName();

    String value = item.getString();

    ...

}

文件域

if (!item.isFormField()) {

    String fieldName = item.getFieldName();

    String fileName = item.getName();

    String contentType = item.getContentType();

    boolean isInMemory = item.isInMemory();

    long sizeInBytes = item.getSize();

    InputStream uploadedStream = item.getInputStream();

    ...

    uploadedStream.close();

}

如何得到 List<FileItem> 对象.

> 简单的方式

// Create a factory for disk-based file items

FileItemFactory factory = new DiskFileItemFactory();

// Create a new file upload handler

ServletFileUpload upload = new ServletFileUpload(factory);

// Parse the request

List /* FileItem */ items = upload.parseRequest(request);

> 复杂的方式

可以为文件的上传加入一些限制条件和其他的属性

// Create a factory for disk-based file items

DiskFileItemFactory factory = new DiskFileItemFactory();

//设置内存中最多可以存放的上传文件的大小, 若超出则把文件写到一个临时文件夹中. 以 byte 为单位

factory.setSizeThreshold(yourMaxMemorySize);

//设置那个临时文件夹

factory.setRepository(yourTempDirectory);

// Create a new file upload handler

ServletFileUpload upload = new ServletFileUpload(factory);

//设置上传文件的总的大小. 也可以设置单个文件的大小.

upload.setSizeMax(yourMaxRequestSize);

// Parse the request

List /* FileItem */ items = upload.parseRequest(request);

下面是简单的上传Servlet

package com.aidata.web;

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.util.List;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;

import org.apache.commons.fileupload.FileUploadException;

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

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

public class UploadServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    protected void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        // 1. 得到 FileItem 的集合 items

        // Create a factory for disk-based file items

        DiskFileItemFactory factory = new DiskFileItemFactory();

        // FileCleaningTracker fileCleaningTracker =

        // FileCleanerCleanup.getFileCleaningTracker(getServletContext());

        // factory.setFileCleaningTracker(fileCleaningTracker);

        // Set factory constraints

        factory.setSizeThreshold(1024 * 500);

        File tempDirectory = new File("d:\\tempDirectory");

        factory.setRepository(tempDirectory);

        // Create a new file upload handler

        ServletFileUpload upload = new ServletFileUpload(factory);

        // Set overall request size constraint

        upload.setSizeMax(1024 * 1024 * 5);

        // Parse the request

        try {

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

            // 2. 遍历 items:

            for (FileItem item : items) {

                // 若是一个一般的表单域, 打印信息

                if (item.isFormField()) {

                    String name = item.getFieldName();

                    String value = item.getString();

                    System.out.println(name + ": " + value);

                }

                // 若是文件域则把文件保存到 d:\\files 目录下.

                else {

                    String fieldName = item.getFieldName();

                    String fileName = item.getName();

                    String contentType = item.getContentType();

                    long sizeInBytes = item.getSize();

                    System.out.println(fieldName);

                    System.out.println(fileName);

                    System.out.println(contentType);

                    System.out.println(sizeInBytes);

                    InputStream in = item.getInputStream();

                    byte[] buffer = new byte[1024];

                    int len = 0;

                    fileName = "d:\\files\\" + fileName;

                    System.out.println(fileName);

                    OutputStream out = new FileOutputStream(fileName);

                    while ((len = in.read(buffer)) != -1) {

                        out.write(buffer, 0, len);

                    }

                    out.close();

                    in.close();

                }

            }

        } catch (FileUploadException e) {

            e.printStackTrace();

        }

    }

}

案例

使用 fileupload 组件完成文件的上传应用

1). 需求:

上传

> 在 upload.jsp 页面上使用 jQuery 实现 "新增一个附件"，"删除附件"，但至少需要保留一个.。

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

    pageEncoding="UTF-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>Insert title here</title>

<script type="text/javascript" src="${pageContext.request.contextPath }/scripts/jquery-1.7.2.js"></script>

<script type="text/javascript">

    $(function(){

        var i = 2;

        $("#addFile").click(function(){

            $(this).parent().parent().before("<tr class='file'><td>File"

                    + i + ":</td><td><input type='file' name='file"

                    + i + "'/></td></tr>"

                    + "<tr class='desc'><td>Desc"

                    + i + ":</td><td><input type='text' name='desc"

                    + i + "'/><button id='delete"

                    + i + "'>删除</button></td></tr>");

            i++;

            //获取新添加的删除按钮

            $("#delete" + (i-1)).click(function(){

                var $tr = $(this).parent().parent();

                $tr.prev("tr").remove();

                $tr.remove();

                //对 i 重写排序

                $(".file").each(function(index){

                    var n = index + 1;

                    $(this).find("td:first").text("File" + n);

                    $(this).find("td:last input").attr("name", "file" + n);

                });

                $(".desc").each(function(index){

                    var n = index + 1;

                    $(this).find("td:first").text("Desc" + n);

                    $(this).find("td:last input").attr("name", "desc" + n);

                });

                i = i - 1;

            });

            return false;

        });

    });

</script>

</head>

<body>

    <font color="red">${message }</font>

    <br><br>

    <form action="fileuploadservlet" method="post" enctype="multipart/form-data">

        <table>

            <tr class="file">

                <td>File1:</td>

                <td><input type="file" name="file1"/></td>

            </tr>

            <tr class="desc">

                <td>Desc1:</td>

                <td><input type="text" name="desc1"/></td>

            </tr>

            <tr>

                <td><input type="submit" id="submit" value="提交"/></td>

                <td><button id="addFile">新增一个附件</button></td>

            </tr>

        </table>

    </form>

</body>

</html>

> 对文件的扩展名和文件的大小进行验证。以下的规则是可配置的，而不是写死在程序中的。

>> 文件的扩展名必须为 pptx, docx, doc
>> 每个文件的大小不能超过 1 M
>> 总的文件大小不能超过 5 M.

upload.properties

exts=pptx,docx,doc

file.max.size=1048576

total.file.max.size=5242880

package com.atguigu.fileupload.app.listener;

import java.io.File;

import java.io.IOException;

import java.io.InputStream;

import java.util.Map;

import java.util.Properties;

import javax.servlet.ServletContextEvent;

import javax.servlet.ServletContextListener;

import com.atguigu.fileupload.app.utils.FileUploadAppProperties;

/**

 * Application Lifecycle Listener implementation class FileUploadAppListener

 *

 */

public class FileUploadAppListener implements ServletContextListener {

    /**

     * Default constructor.

     */

    public FileUploadAppListener() {

        // TODO Auto-generated constructor stub

    }

    /**

     * @see ServletContextListener#contextInitialized(ServletContextEvent)

     */

    public void contextInitialized(ServletContextEvent arg0) {

        InputStream in = getClass().getClassLoader().getResourceAsStream("/upload.properties");

        Properties properties = new Properties();

        try {

            properties.load(in);

            for(Map.Entry<Object, Object> prop: properties.entrySet()){

                String propertyName = (String) prop.getKey();

                String propertyValue = (String) prop.getValue();

                FileUploadAppProperties.getInstance().addProperty(propertyName, propertyValue);

            }

        } catch (IOException e) {

            e.printStackTrace();

        }

    }

    /**

     * @see ServletContextListener#contextDestroyed(ServletContextEvent)

     */

    public void contextDestroyed(ServletContextEvent arg0) {

        // TODO Auto-generated method stub

    }

}

package com.atguigu.fileupload.app.utils;

import java.util.HashMap;

import java.util.Map;

public class FileUploadAppProperties {

    private Map<String, String> properties = new HashMap<>();

    private FileUploadAppProperties(){}

    private static FileUploadAppProperties instance = new FileUploadAppProperties();

    public static FileUploadAppProperties getInstance() {

        return instance;

    }

    public void addProperty(String propertyName, String propertyValue){

        properties.put(propertyName, propertyValue);

    }

    public String getProperty(String propertyName){

        return properties.get(propertyName);

    }

}

> 若验证失败, 则在 upload.jsp 页面上显示错误消息:

>> 若某一个文件不符合要求: xxx 文件扩展名不合法或 xxx 文件大小超过 1 M
>> 总的文件大小不能超过 5 M.

> 若验证通过, 则进行文件的上传操作

>> 文件上传, 并给一个不能和其他文件重复的名字, 但扩展名不变
>> 在对应的数据表中添加一条记录.

id file_name file_path file_desc

package com.atguigu.fileupload.app.beans;

import java.util.ArrayList;

import java.util.List;

import com.google.gson.Gson;

public class FileUploadBean {

    public static void main(String[] args) {

        FileUploadBean bean = new FileUploadBean("ABC", "e:\\abc.txt", "aabbcc");

        Gson gson = new Gson();

        String jsonStr = gson.toJson(bean);

        System.out.println(jsonStr);

        List<FileUploadBean> beans = new ArrayList<>();

        beans.add(bean);

        beans.add(new FileUploadBean("def", "e:\\def.txt", "ddeeff"));

        jsonStr = gson.toJson(beans);

        System.out.println(jsonStr);

    }

    private Integer id;

    // 文件名

    private String fileName;

    // 文件的路径

    private String filePath;

    // 文件的描述

    private String fileDesc;

    public Integer getId() {

        return id;

    }

    public void setId(Integer id) {

        this.id = id;

    }

    public String getFileName() {

        return fileName;

    }

    public void setFileName(String fileName) {

        this.fileName = fileName;

    }

    public String getFilePath() {

        return filePath;

    }

    public void setFilePath(String filePath) {

        this.filePath = filePath;

    }

    public String getFileDesc() {

        return fileDesc;

    }

    public void setFileDesc(String fileDesc) {

        this.fileDesc = fileDesc;

    }

    public FileUploadBean(String fileName, String filePath, String fileDesc) {

        super();

        this.fileName = fileName;

        this.filePath = filePath;

        this.fileDesc = fileDesc;

    }

    public FileUploadBean() {

        // TODO Auto-generated constructor stub

    }

}

package com.atguigu.fileupload.app.servlet;

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.io.UnsupportedEncodingException;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import java.util.Random;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;

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

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

import com.atguigu.fileupload.app.beans.FileUploadBean;

import com.atguigu.fileupload.app.db.UploadFileDao;

import com.atguigu.fileupload.app.exception.InvalidExtNameException;

import com.atguigu.fileupload.app.utils.FileUploadAppProperties;

import com.atguigu.fileupload.app.utils.FileUtils;

public class FileUploadServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    private static final String FILE_PATH = "/WEB-INF/files/";

    private static final String TEMP_DIR = "d:\\tempDirectory";

    private UploadFileDao dao = new UploadFileDao();

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        request.setCharacterEncoding("UTF-8");

        String path = null;

        //获取 ServletFileUpload 对象.

        ServletFileUpload upload = getServletFileUpload();

        try {

            //把需要上传的 FileItem 都放入到该 Map 中

            //键: 文件的待存放的路径, 值: 对应的 FileItem 对象

            Map<String, FileItem> uploadFiles = new HashMap<String, FileItem>();

            //解析请求, 得到 FileItem 的集合.

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

            //1. 构建 FileUploadBean 的集合, 同时填充 uploadFiles

            List<FileUploadBean> beans = buildFileUploadBeans(items, uploadFiles);

            //2. 校验扩展名:

            vaidateExtName(beans);

            //3. 校验文件的大小: 在解析时, 已经校验了, 我们只需要通过异常得到结果. 

            //4. 进行文件的上传操作.

            upload(uploadFiles);

            //5. 把上传的信息保存到数据库中

            saveBeans(beans);

            //6. 删除临时文件夹的临时文件

            FileUtils.delAllFile(TEMP_DIR);

            path = "/app/success.jsp";

        } catch (Exception e) {

            e.printStackTrace();

            path = "/app/upload.jsp";

            request.setAttribute("message", e.getMessage());

        }

        request.getRequestDispatcher(path).forward(request, response);

    }

    private void saveBeans(List<FileUploadBean> beans) {

        dao.save(beans);

    }

    /**

     * 文件上传前的准备工作. 得到 filePath 和 InputStream

     * @param uploadFiles

     * @throws IOException

     */

    private void upload(Map<String, FileItem> uploadFiles) throws IOException {

        for(Map.Entry<String, FileItem> uploadFile: uploadFiles.entrySet()){

            String filePath = uploadFile.getKey();

            FileItem item = uploadFile.getValue();

            upload(filePath, item.getInputStream());

        }

    }

    /**

     * 文件上传的 IO 方法.

     *

     * @param filePath

     * @param inputStream

     * @throws IOException

     */

    private void upload(String filePath, InputStream inputStream) throws IOException {

        OutputStream out = new FileOutputStream(filePath);

        byte [] buffer = new byte[1024];

        int len = 0;

        while((len = inputStream.read(buffer)) != -1){

            out.write(buffer, 0, len);

        }

        inputStream.close();

        out.close();

        System.out.println(filePath);

    }

    /**

     * 校验扩展名是否合法

     * @param beans:

     */

    private void vaidateExtName(List<FileUploadBean> beans) {

        String exts = FileUploadAppProperties.getInstance().getProperty("exts");

        List<String> extList = Arrays.asList(exts.split(","));

        System.out.println(extList);

        for(FileUploadBean bean: beans){

            String fileName = bean.getFileName();

            System.out.println(fileName.indexOf(".")); 

            String extName = fileName.substring(fileName.lastIndexOf(".") + 1);

            System.out.println(extName); 

            if(!extList.contains(extName)){

                throw new InvalidExtNameException(fileName + "文件的扩展名不合法");

            }

        }

    }

    /**

     * 利用传入的 FileItem 的集合, 构建 FileUploadBean 的集合, 同时填充 uploadFiles

     *

     * FileUploadBean 对象封装了: id, fileName, filePath, fileDesc

     * uploadFiles: Map<String, FileItem> 类型, 存放文件域类型的  FileItem. 键: 待保存的文件的名字 ,值: FileItem 对象

     *

     * 构建过程:

     * 1. 对传入 FileItem 的集合进行遍历. 得到 desc 的那个 Map. 键: desc 的 fieldName(desc1, desc2 ...).

     * 值: desc 的那个输入的文本值

     *

     * 2. 对传入 FileItem 的集合进行遍历. 得到文件域的那些 FileItem 对象, 构建对应的 key (desc1 ....) 来获取其 desc.

     * 构建的 FileUploadBean 对象, 并填充 beans 和 uploadFiles

     *

     * @param items

     * @param uploadFiles

     * @return

     * @throws UnsupportedEncodingException

     */

    private List<FileUploadBean> buildFileUploadBeans(List<FileItem> items, Map<String, FileItem> uploadFiles) throws UnsupportedEncodingException {

        List<FileUploadBean> beans = new ArrayList<>();

        Map<String, String> descs = new HashMap<>();

        for(int i = 0; i < items.size(); i++){

            FileItem item = items.get(i);

            if(item.isFormField()){

                //desc1 或 desc2 ...

                String fieldName = item.getFieldName();

                String desc = item.getString("UTF-8");

                descs.put(fieldName, desc);

            }

        }

        for(int i = 0; i < items.size(); i++){

            FileItem item = items.get(i);

            FileUploadBean bean = null;

            if(!item.isFormField()){

                String fieldName = item.getFieldName();

                String descName = "desc" + fieldName.substring(fieldName.length() - 1);

                String desc = descs.get(descName); 

                //对应文件名

                String fileName = item.getName();

                String filePath = getFilePath(fileName);

                bean = new FileUploadBean(fileName, filePath, desc);

                beans.add(bean);

                uploadFiles.put(bean.getFilePath(), item);

            }

        }

        return beans;

    }

    /**

     * 根据跟定的文件名构建一个随机的文件名

     * 1. 构建的文件的文件名的扩展名和给定的文件的扩展名一致

     * 2. 利用 ServletContext 的 getRealPath 方法获取的绝对路径

     * 3. 利用了 Random 和 当前的系统时间构建随机的文件的名字

     *

     * @param fileName

     * @return

     */

    private String getFilePath(String fileName) {

        String extName = fileName.substring(fileName.lastIndexOf("."));

        Random random = new Random();

        String filePath = getServletContext().getRealPath(FILE_PATH) + "\\" + System.currentTimeMillis() + random.nextInt(100000) + extName;

        return filePath;

    }

    /**

     * 构建 ServletFileUpload 对象

     * 从配置文件中读取了部分属性, 用户设置约束.

     * 该方法代码来源于文档.

     * @return

     */

    private ServletFileUpload getServletFileUpload() {

        String fileMaxSize = FileUploadAppProperties.getInstance().getProperty("file.max.size");

        String totalFileMaxSize = FileUploadAppProperties.getInstance().getProperty("total.file.max.size");

        DiskFileItemFactory factory = new DiskFileItemFactory();

        factory.setSizeThreshold(1024 * 500);

        File tempDirectory = new File(TEMP_DIR);

        factory.setRepository(tempDirectory);

        ServletFileUpload upload = new ServletFileUpload(factory);

        upload.setSizeMax(Integer.parseInt(totalFileMaxSize));

        upload.setFileSizeMax(Integer.parseInt(fileMaxSize));

        return upload;

    }

}

package com.atguigu.fileupload.app.db;

import java.sql.Connection;

import java.sql.SQLException;

import javax.sql.DataSource;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class JDBCUtils {

    private static DataSource dataSource = null;

    static{

        dataSource = new ComboPooledDataSource("javawebapp");

    }

    public static Connection getConnection(){

        try {

            return dataSource.getConnection();

        } catch (SQLException e) {

            e.printStackTrace();

            throw new DBException("");

        }

    }

    public static void release(Connection connection) {

        try {

            if(connection != null){

                connection.close();

            }

        } catch (SQLException e) {

            e.printStackTrace();

            throw new DBException("");

        }

    }

}

package com.atguigu.fileupload.app.db;

import java.lang.reflect.ParameterizedType;

import java.lang.reflect.Type;

import java.sql.Connection;

import java.sql.SQLException;

import java.util.List;

import org.apache.commons.dbutils.QueryRunner;

import org.apache.commons.dbutils.handlers.ArrayHandler;

import org.apache.commons.dbutils.handlers.BeanHandler;

import org.apache.commons.dbutils.handlers.BeanListHandler;

public class DAO<T>{

    public static QueryRunner runner = new QueryRunner();

    private Class<T> clazz;

    public DAO() {

        Type type = getClass().getGenericSuperclass();

        if(type instanceof ParameterizedType){

            ParameterizedType pt = (ParameterizedType) type;

            Type [] parameterArgs = pt.getActualTypeArguments();

            if(parameterArgs != null && parameterArgs.length > 0){

                if(parameterArgs[0] instanceof Class){

                    clazz = (Class<T>) parameterArgs[0];

                }

            }

        }

    }

    protected void update(Connection conn, String sql, Object ... args) throws SQLException{

        runner.update(conn, sql, args);

    }

    protected T get(Connection conn, String sql, Object ... args) throws SQLException{

        return runner.query(conn, sql, new BeanHandler<>(clazz), args);

    }

    protected List<T> getForList(Connection conn, String sql, Object ... args) throws SQLException{

        return runner.query(conn, sql, new BeanListHandler<>(clazz), args);

    }

    protected <E> E getValue(Connection conn, String sql, Object ... args) throws SQLException{

        E result = null;

        result = (E) runner.query(conn, sql, new ArrayHandler(), args)[0];

        return result;

    }

}

package com.atguigu.fileupload.app.db;

import java.sql.Connection;

import java.util.List;

import com.atguigu.fileupload.app.beans.FileUploadBean;

public class UploadFileDao extends DAO<FileUploadBean>{

    public List<FileUploadBean> getFiles(){

        Connection conn = null;

        try {

            conn = JDBCUtils.getConnection();

            String sql = "SELECT id, file_name fileName, file_path filePath, " +

                    "file_desc fileDesc FROM upload_files";

            return getForList(conn, sql);

        } catch (Exception e) {

            e.printStackTrace();

        } finally{

            JDBCUtils.release(conn);

        }

        return null;

    } 

    public void save(List<FileUploadBean> uploadFiles){

        Connection conn = null;

        try {

            conn = JDBCUtils.getConnection();

            String sql = "INSERT INTO upload_files (file_name, file_path, file_desc) VALUES " +

                    "(?, ?, ?)";

            for(FileUploadBean file: uploadFiles){

                update(conn, sql, file.getFileName(), file.getFilePath(), file.getFileDesc());

            }

        } catch (Exception e) {

            e.printStackTrace();

        } finally{

            JDBCUtils.release(conn);

        }

    }

}

package com.atguigu.fileupload.app.db;

public class DBException extends RuntimeException {

    /**

     *

     */

    private static final long serialVersionUID = 1L;

    public DBException() {

        // TODO Auto-generated constructor stub

    }

    public DBException(String msg) {

        super(msg);

    }

    public DBException(String msg, Exception ex) {

        super(msg, ex);

    }

}

下载

问题: 如何清除上传文件临时文件夹的文件.

文件的下载:

1). 步骤:

I. 设置 contentType 响应头: 设置响应的类型是什么 ? 通知浏览器是个下载的文件

response.setContentType("application/x-msdownload");

II. 设置 Content-Disposition 响应头: 通知浏览器不再有浏览器来自行处理(或打开)要下载的文件, 而由用户手工完成

response.setHeader("Content-Disposition", "attachment;filename=abc.txt");

III. 具体的文件: 可以调用 response.getOutputStream 的方式, 以 IO 流的方式发送给客户端.

OutputStream out = response.getOutputStream();

String pptFileName = "C:\\Users\\Think Pad\\Desktop\\__正在上课__\\11.尚硅谷_JavaWEB_监听器.pptx";

InputStream in = new FileInputStream(pptFileName);

byte [] buffer = new byte[1024];

int len = 0;

while((len = in.read(buffer)) != -1){

out.write(buffer, 0, len);

}

in.close();

package com.atguigu.download.servlet;

import java.io.FileInputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.net.URLEncoder;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 * Servlet implementation class DownloadServlet

 */

public class DownloadServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    /**

     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)

     */

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        response.setContentType("application/x-msdownload"); 

        String fileName = "文件下载.pptx";

        response.setHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8"));

        OutputStream out = response.getOutputStream();

        String pptFileName = "C:\\Users\\Think Pad\\Desktop\\__正在上课__\\11.尚硅谷_JavaWEB_监听器.pptx";

        InputStream in = new FileInputStream(pptFileName);

        byte [] buffer = new byte[1024];

        int len = 0;

        while((len = in.read(buffer)) != -1){

            out.write(buffer, 0, len);

        }

        in.close();

    }

}

巴特西

JavaWeb(九)：上传和下载

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