处理文件上传与下载

package com.loaderman.demo;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URLEncoder;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.UUID;

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.FileItemFactory;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

/**
 * 处理文件上传与下载
 * @author Jie.Yuan
 *
 */
public class FileServlet extends HttpServlet {

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

        // 获取请求参数： 区分不同的操作类型
        String method = request.getParameter("method");
        if ("upload".equals(method)) {
            // 上传
            upload(request,response);
        }

        else if ("downList".equals(method)) {
            // 进入下载列表
            downList(request,response);
        }

        else if ("down".equals(method)) {
            // 下载
            down(request,response);
        }
    }


    /**
     * 1. 上传
     */
    private void upload(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        try {
            // 1. 创建工厂对象
            FileItemFactory factory = new DiskFileItemFactory();
            // 2. 文件上传核心工具类
            ServletFileUpload upload = new ServletFileUpload(factory);
            // 设置大小限制参数
            upload.setFileSizeMax(10*1024*1024);    // 单个文件大小限制
            upload.setSizeMax(50*1024*1024);        // 总文件大小限制
            upload.setHeaderEncoding("UTF-8");        // 对中文文件编码处理

            // 判断
            if (upload.isMultipartContent(request)) {
                // 3. 把请求数据转换为list集合
                List<FileItem> list = upload.parseRequest(request);
                // 遍历
                for (FileItem item : list){
                    // 判断：普通文本数据
                    if (item.isFormField()){
                        // 获取名称
                        String name = item.getFieldName();
                        // 获取值
                        String value = item.getString();
                        System.out.println(value);
                    }
                    // 文件表单项
                    else {
                        /******** 文件上传 ***********/
                        // a. 获取文件名称
                        String name = item.getName();
                        // ----处理上传文件名重名问题----
                        // a1. 先得到唯一标记
                        String id = UUID.randomUUID().toString();
                        // a2. 拼接文件名
                        name = id + "#" + name;

                        // b. 得到上传目录
                        String basePath = getServletContext().getRealPath("/upload");
                        // c. 创建要上传的文件对象
                        File file = new File(basePath,name);
                        // d. 上传
                        item.write(file);
                        item.delete();  // 删除组件运行时产生的临时文件
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }


    }


    /**
     * 2. 进入下载列表
     */
    private void downList(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        // 实现思路：先获取upload目录下所有文件的文件名，再保存；跳转到down.jsp列表展示

        //1. 初始化map集合Map<包含唯一标记的文件名, 简短文件名>  ;
        Map<String,String> fileNames = new HashMap<String,String>();

        //2. 获取上传目录，及其下所有的文件的文件名
        String bathPath = getServletContext().getRealPath("/upload");
        // 目录
        File file = new File(bathPath);
        // 目录下，所有文件名
        String list[] = file.list();
        // 遍历，封装
        if (list != null && list.length > 0){
            for (int i=0; i<list.length; i++){
                // 全名
                String fileName = list[i];
                // 短名
                String shortName = fileName.substring(fileName.lastIndexOf("#")+1);
                // 封装
                fileNames.put(fileName, shortName);
            }
        }

        // 3. 保存到request域
        request.setAttribute("fileNames", fileNames);
        // 4. 转发
        request.getRequestDispatcher("/downlist.jsp").forward(request, response);

    }


    /**
     *  3. 处理下载
     */
    private void down(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        // 获取用户下载的文件名称(url地址后追加数据,get)
        String fileName = request.getParameter("fileName");
        fileName = new String(fileName.getBytes("ISO8859-1"),"UTF-8");

        // 先获取上传目录路径
        String basePath = getServletContext().getRealPath("/upload");
        // 获取一个文件流
        InputStream in = new FileInputStream(new File(basePath,fileName));

        // 如果文件名是中文，需要进行url编码
        fileName = URLEncoder.encode(fileName, "UTF-8");
        // 设置下载的响应头
        response.setHeader("content-disposition", "attachment;fileName=" + fileName);

        // 获取response字节流
        OutputStream out = response.getOutputStream();
        byte[] b = new byte[1024];
        int len = -1;
        while ((len = in.read(b)) != -1){
            out.write(b, 0, len);
        }
        // 关闭
        out.close();
        in.close();


    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        this.doGet(request, response);
    }

}

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    
    <title>index</title>
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
  </head>

  <body>
  <a href="${pageContext.request.contextPath }/upload.jsp">文件上传</a> &nbsp;&nbsp;&nbsp;
  <a href="${pageContext.request.contextPath }/fileServlet?method=downList">文件下载</a>

  </body>

</html>

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    
    <title>下载列表</title>
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
  </head>
  
  <body>    
    <table border="1" align="center">
        <tr>
            <th>序号</th>
            <th>文件名</th>
            <th>操作</th>
        </tr>
        <c:forEach var="en" items="${requestScope.fileNames}" varStatus="vs">
            <tr>
                <td>${vs.count }</td>
                <td>${en.value }</td>
                <td>
                    <%--<a href="${pageContext.request.contextPath }/fileServlet?method=down&..">下载</a>--%>
                    <!-- 构建一个地址  -->
                    <c:url var="url" value="fileServlet">
                        <c:param name="method" value="down"></c:param>
                        <c:param name="fileName" value="${en.key}"></c:param>
                    </c:url>
                    <!-- 使用上面地址 -->
                    <a href="${url }">下载</a>
                </td>
            </tr>
        </c:forEach>
    </table>          
  </body>
</html>

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    
    <title>upload</title>
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
  </head>
  
  <body>    
       <form name="frm_test" action="${pageContext.request.contextPath }/fileServlet?method=upload" method="post" enctype="multipart/form-data">
            <%--<input type="hidden" name="method" value="upload">--%>
            
            用户名：<input type="text" name="userName">  <br/>
           文件：   <input type="file" name="file_img">   <br/>
           
           <input type="submit" value="提交">
        </form>
  </body>
</html>