JAVAWEB之文件的上传下载

文件上传下载

文件上传:

本篇文章使用的文件上传的例子使用的都是原生技术，servelt+jdbc+fileupload插件，这也是笔者的习惯，当接触到某些从未接触过的东西时，总是喜欢用最原始的东西将他们表达出来。下面是具体的步骤，大家可以跟着我一步一步的用apache的fileupload插件来完成文件的上传下载。

1.创建一个web工程，我们这里取名为fileupload

2.导入相关jar包，，数据源使用的是apache-c3p0数据源，以及上传下载插件包，goson库，以及mysql驱动包，大家可以去https://mvnrepository.com/自行下载，系在前请核实jar版本，防止jar冲突。

3.src目录下创建upload.properties文件，用于配置文件上传的限制参数。

exts=pptx,docx,doc
file.max.size=1048576
total.file.max.size=5242880

4.创建工程包结构， 

5.创建读取upload.properties的监听器类，初始化上传文件的限制参数，具体代码如下:

package com.sunyard.listener;

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.sunyard.utils.FileUploadAppProperties;

/**
 * <p>初始化上传文件限制参数的监听器</p>
 * @author:774346810@qq.com
 * @date:2017-6-16
 */
public class FileUploadAppListener implements ServletContextListener{

    @Override
    public void contextDestroyed(ServletContextEvent arg0) {
        
    }

    @Override
    public void contextInitialized(ServletContextEvent arg0) {
        InputStream in = this.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();
        }
    }

}

 6.配置web.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0" 
    xmlns="http://java.sun.com/xml/ns/javaee" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
    http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
  <display-name></display-name>    
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
  
  <!-- 初始化监听器 -->
  <listener>
      <listener-class>com.sunyard.listener.FileUploadAppListener</listener-class>
  </listener>
  
  <!-- 注册上传servlet -->
  <servlet>
      <servlet-name>upload</servlet-name>
      <servlet-class>com.sunyard.servlet.FileUploadServlet</servlet-class>
  </servlet>
  <servlet-mapping>
      <servlet-name>upload</servlet-name>
      <url-pattern>/upload</url-pattern>
  </servlet-mapping>
  
  <!-- 注册下载servlet -->
  <servlet>
     <servlet-name>download</servlet-name>
     <servlet-class>com.sunyard.servlet.DownLoadServlet</servlet-class>
  </servlet>
  <servlet-mapping>
      <servlet-name>download</servlet-name>
      <url-pattern>/download</url-pattern>
  </servlet-mapping>
  
</web-app>

配置监听器，以及文件上传servlet和文件下载servlet。

6.完善工程所需要的类，

1）创建上传下载实体，FileUploadBean

package com.sunyard.bean;

/**
 * <p>文件上传实体</p>
 * @author:774346810@qq.com
 * @date:2017-6-16
 */
public class FileUploadBean {
    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(Integer id, String fileName, String filePath,
            String fileDesc) {
        this.id = id;
        this.fileName = fileName;
        this.filePath = filePath;
        this.fileDesc = fileDesc;
    }

    public FileUploadBean() {
        
    }
}

2）dao操作自定义异常类

package com.sunyard.db;

public class DBException extends Exception {

    /**
     * 
     */
    private static final long serialVersionUID = -1547402862446161034L;
    
    public DBException() {
    }
    
    public DBException(String msg) {
        super(msg);
    }
    
    public DBException(String msg, Exception ex) {
        super(msg, ex);
    }
}

3）JDBC连接工具类

package com.sunyard.db;

import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

public class JDBCUtils {
    public static void release(ResultSet rs, 
            Statement statement, Connection conn) {
        if(rs != null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        
        
        if (statement != null) {
            try {
                statement.close();
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }

        if (conn != null) {
            try {
                conn.close();
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }
    }
    
    /**
     * 关闭 Statement 和 Connection
     * @param statement
     * @param conn
     */
    public static void release(Statement statement, Connection conn) {
        if (statement != null) {
            try {
                statement.close();
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }

        if (conn != null) {
            try {
                conn.close();
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }
    }

    /**
     * 1. 获取连接的方法. 通过读取配置文件从数据库服务器获取一个连接.
     * 
     * @return
     * @throws Exception
     */
    public static Connection getConnection() throws Exception {
        // 1. 准备连接数据库的 4 个字符串.
        // 1). 创建 Properties 对象
        Properties properties = new Properties();

        // 2). 获取 jdbc.properties 对应的输入流
        InputStream in = JDBCUtils.class.getClassLoader().getResourceAsStream(
                "jdbc.properties");

        // 3). 加载 2） 对应的输入流
        properties.load(in);

        // 4). 具体决定 user, password 等4 个字符串.
        String user = properties.getProperty("user");
        String password = properties.getProperty("password");
        String jdbcUrl = properties.getProperty("jdbcUrl");
        String driver = properties.getProperty("driver");

        // 2. 加载数据库驱动程序(对应的 Driver 实现类中有注册驱动的静态代码块.)
        Class.forName(driver);

        // 3. 通过 DriverManager 的 getConnection() 方法获取数据库连接.
        return DriverManager.getConnection(jdbcUrl, user, password);
    }
}

5）文件上传下载的dao层方法

package com.sunyard.db;

import java.sql.Connection;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

import com.mysql.jdbc.PreparedStatement;
import com.mysql.jdbc.Statement;
import com.sunyard.bean.FileUploadBean;

/**
 * <p>文件上传下载dao</p>
 * @author:774346810@qq.com
 * @date:2017-6-25
 */
public class UploadFileDao {
    
    /**
     * 查询所有文件信息
     * @return
     */
    public List<FileUploadBean> getFiles(){
        Connection conn = null;
        Statement statement = null;
        ResultSet rs = null;
        
        List<FileUploadBean> beans = new ArrayList<FileUploadBean>();
        
        try {
            conn = JDBCUtils.getConnection();
            String sql = "SELECT id, file_name fileName, file_path filePath, " +
                    "file_desc fileDesc FROM upload_files";
            statement = (Statement) conn.createStatement();
            rs = statement.executeQuery(sql);
            
            while(rs.next()){
                Integer id = rs.getInt("id");
                String fileName = rs.getString("file_name");
                String filePath = rs.getString("file_path");
                String fileDesc = rs.getString("file_desc");
                
                FileUploadBean bean = new FileUploadBean(id, fileName, filePath, fileDesc);
                beans.add(bean);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally{
            JDBCUtils.release(rs, statement, conn);
        }
        
        return beans;
    } 
    
    /**
     * 将已经上传的文件存放数据库中
     * @param uploadFiles
     */
    public void save(List<FileUploadBean> uploadFiles){
        
        Connection conn = null;
        PreparedStatement preparedStatement = null;
        
        try {
            conn = JDBCUtils.getConnection();
            String sql = "INSERT INTO upload_files (file_name, file_path, file_desc) VALUES " +
                    "(?, ?, ?)";
            preparedStatement = (PreparedStatement) conn.prepareStatement(sql);
            
            for(int i = 0;i < uploadFiles.size();i++){
                FileUploadBean fileUploadBean = uploadFiles.get(i);
                preparedStatement.setString(1, fileUploadBean.getFileName());
                preparedStatement.setString(2, fileUploadBean.getFilePath());
                preparedStatement.setString(3, fileUploadBean.getFileDesc());
                preparedStatement.executeUpdate();
            }
            
        } catch (Exception e) {
            e.printStackTrace();
        } finally{
            JDBCUtils.release(null, preparedStatement, conn);
        }
        
    }
}

6）自定义异常类

package com.sunyard.exception;

public class InvalidExtNameException extends RuntimeException{

    /**
     * 
     */
    private static final long serialVersionUID = -1478119693559275850L;
    
    public InvalidExtNameException(String msg){
        super(msg);
    }
}

7）处理文件上传的servlet

package com.sunyard.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.sunyard.bean.FileUploadBean;
import com.sunyard.db.UploadFileDao;
import com.sunyard.exception.InvalidExtNameException;
import com.sunyard.utils.FileUploadAppProperties;

public class FileUploadServlet extends HttpServlet{

    private static final long serialVersionUID = 6227133615299280663L;
    
    private static final String FILE_PATH = "/WEB-INF/files/";//类路径
    
    private static final String TEMP_DIR = "d:\tempDirectory";//文件临时存储路径
    
    UploadFileDao uploadFileDao = new UploadFileDao();

    @Override
    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);
            
            path = "/app/success.jsp";
        } catch (Exception e) {
            e.printStackTrace();
        }
        
        request.getRequestDispatcher(path).forward(request, response);
    }
    
    private void saveBeans(List<FileUploadBean> beans) {
        uploadFileDao.save(beans);
    }

    /**
     * 进行文件上传操作
     * @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); 
    }

    /**
     * 校验文件扩展名是否合法
     * @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<FileUploadBean>();
        
        Map<String, String> descs = new HashMap<String, String>();
        
        //处理普通的表单体
        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);
            }
        }
        
        //处理文件表单体
        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;
    }

    /**
     * 获取 ServletFileUpload 对象. 
     * @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;
    }
    
}

8）用于存储文件上传的单例工具类FileUploadAppProperties

package com.sunyard.utils;

import java.util.HashMap;
import java.util.Map;

/**
 * <p>上传下载参数单例类</p>
 * @author:774346810@qq.com
 * @date:2017-6-16
 */
public class FileUploadAppProperties {
    
    private Map<String, String> properties = new HashMap<String, String>();
    
    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);
    }
}

9）JDBC连接数据库的参数properties文件

#driver=oracle.jdbc.driver.OracleDriver
#jdbcUrl=jdbc:oracle:thin:@localhost:1521:orcl
#user=scott
#password=java

driver=com.mysql.jdbc.Driver
jdbcUrl=jdbc:mysql://localhost:3306/upload
user=root
password=123456

10）jQuery开发的静态资源文件

11）文件上传的页面upload.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'upload.jsp' starting page</title>
    
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->
    <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="upload" 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>

将项目部署服务器，启动，访问http://127.0.0.1:8080/fileupload/app/upload.jsp后出现下面的页面

点击上传，就可以完成文件上传的功能。

可以去服务器和数据库中查看是否上传成功，如下：

 

至此，文件上传功能完成。

 

***************************************************************

文件下载：

为了演示，我们将需要下载的文件内容写死，处理下载的servlet代码如下。

package com.sunyard.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;

import com.sunyard.db.UploadFileDao;

/**
 * <p>下载servlet</p>
 * @author:774346810@qq.com
 * @date:2017-6-18
 */
public class DownLoadServlet extends HttpServlet{
    
    private static final long serialVersionUID = -1409324086440387753L;
    
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("application/x-msdownload");
        
        String fileName = "文件下载.docx";
        response.setHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8"));
        
        OutputStream out = response.getOutputStream();
        String pptFileName = "D:\apache-tomcat-6.0.16\webapps\fileupload\WEB-INF\files\149837444825180585.docx";
        
        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();
    }
    
}

同样，开启服务，打开浏览器访问

既可以得到需要你下载的文件。

至此，文件上传下载的小案例都在这里了。需要下载demo的同学我已经把工程放在我的百度网盘上大家可以自行下载：

http://pan.baidu.com/s/1pLc6Icb