本人闲来无事，写了个servlet，实现上传下载功能。启动服务后，可以在一个局域网内当一个小小的文件服务器。
一、准备工作
下载两个jar包：
commons-fileupload-1.3.1.jar
commons-io-2.2.jar
二、创建一个web工程
我的工程名叫：z-upload
三、配置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" 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"> <display-name>z-upload</display-name> <servlet> <servlet-name>UploadService</servlet-name> <servlet-class>com.syz.servlet.UploadService</servlet-class> </servlet> <servlet-mapping> <servlet-name>UploadService</servlet-name> <url-pattern>/*</url-pattern> </servlet-mapping></web-app>
从以上配置可以看出，我的servlet类是UploadService，匹配的url是/*，意思是匹配所有访问url。
四、写servlet类
package com.syz.servlet;import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.io.PrintWriter;import java.text.SimpleDateFormat;import java.util.Date;import java.util.Iterator;import java.util.List;import javax.servlet.ServletContext;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.ProgressListener;import org.apache.commons.fileupload.disk.DiskFileItemFactory;import org.apache.commons.fileupload.servlet.ServletFileUpload;public class UploadService extends HttpServlet { public static final String LIST = "/list"; public static final String FORM = "/form"; public static final String HANDLE = "/handle"; public static final String DOWNLOAD = "/download"; public static final String DELETE = "/delete"; public static final String UPLOAD_DIR = "/upload"; private static final long serialVersionUID = 2170797039752860765L; public void execute(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { System.out.println("execute..."); System.out.println("------------begin---------------"); req.setCharacterEncoding("UTF-8"); String host = req.getRemoteHost(); System.out.println("host:" + host); String uri = req.getRequestURI(); System.out.println("uri:" + uri); ServletContext servletContext = this.getServletConfig() .getServletContext(); // 上传文件的基本路径 String basePath = servletContext.getRealPath(UPLOAD_DIR); // 上下文路径 String contextPath = servletContext.getContextPath(); System.out.println("contextPath:" + contextPath); // 截取上下文之后的路径 String action = uri.substring(contextPath.length()); System.out.println("action:" + action); // 依据action不同进行不同的处理 if (action.equals(FORM)) { form(contextPath, resp); } else if (action.equals(HANDLE)) { boolean isMultipart = ServletFileUpload.isMultipartContent(req); System.out.println("isMultipart:" + isMultipart); if (!isMultipart) { return; } DiskFileItemFactory factory = new DiskFileItemFactory(); File repository = (File) servletContext .getAttribute(ServletContext.TEMPDIR); System.out.println("repository:" + repository.getAbsolutePath()); System.out.println("basePath:" + basePath); factory.setSizeThreshold(1024 * 100); factory.setRepository(repository); ServletFileUpload upload = new ServletFileUpload(factory); // 创建监听 ProgressListener progressListener = new ProgressListener() { public void update(long pBytesRead, long pContentLength, int pItems) { System.out.println("当前文件大小:" + pContentLength + "/t已经处理:" + pBytesRead); } }; upload.setProgressListener(progressListener); List<FileItem> items = null; try { items = upload.parseRequest(req); System.out.println("items size:" + items.size()); Iterator<FileItem> ite = items.iterator(); while(ite.hasNext()){ FileItem item = ite.next(); if(item.isFormField()){ // handle FormField }else{ // handle file String fieldName = item.getFieldName(); String fileName = item.getName(); fileName = fileName.substring( fileName.lastIndexOf(File.separator) + 1); String contentType = item.getContentType(); boolean isInMemory = item.isInMemory(); long sizeInBytes = item.getSize(); System.out.println(fieldName + "/t" + fileName + "/t" + contentType + "/t" + isInMemory + "/t" + sizeInBytes); File file = new File( basePath + "/" + fileName + "_" + getSuffix()); // item.write(file); InputStream in = item.getInputStream(); OutputStream out = new FileOutputStream(file); byte[] b = new byte[1024]; int n = 0; while ((n = in.read(b)) != -1) { out.write(b, 0, n); } out.flush(); in.close(); out.close(); } } // 处理完后重定向到文件列表页面 String href1 = contextPath + LIST; resp.sendRedirect(href1); } catch (FileUploadException e) { e.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } } else if (action.equals(LIST)) { list(contextPath, basePath, resp); } else if (action.equals(DOWNLOAD)) { String id = req.getParameter("id"); System.out.println("id:" + id); if (id == null) { return; } File file = new File(basePath); File[] list = file.listFiles(); int len = list.length; boolean flag = false; for (int i = 0; i < len; i++) { File f = list[i]; String fn = f.getName(); if (f.isFile() && fn.lastIndexOf("_") > -1) { String fid = fn.substring(fn.lastIndexOf("_")); if (id.equals(fid)) { download(f, resp); flag = true; break; } } } if (!flag) { notfound(contextPath, resp); } } else if (action.equals(DELETE)) { String id = req.getParameter("id"); System.out.println("id:" + id); if (id == null) { return; } File file = new File(basePath); File[] list = file.listFiles(); int len = list.length; boolean flag = false; for (int i = 0; i < len; i++) { File f = list[i]; String fn = f.getName(); if (f.isFile() && fn.lastIndexOf("_") > -1) { String fid = fn.substring(fn.lastIndexOf("_")); if (id.equals(fid)) { f.delete(); flag = true; break; } } } if (flag) { // 处理完后重定向到文件列表页面 String href1 = contextPath + LIST; resp.sendRedirect(href1); } else { notfound(contextPath, resp); } } else { show404(contextPath, resp); } System.out.println("------------end---------------"); } private void show404(String contextPath, HttpServletResponse resp) throws IOException { resp.setContentType("text/html;charset=utf-8"); PrintWriter out = resp.getWriter(); String href1 = contextPath + LIST; out.write("<html>"); out.write("<head><title>404</title></thead>"); out.write("<body>"); out.write("<b>您所访问的页面不存在！<a href='" + href1 + "'>点击</a>返回文件列表</b>"); out.write("</body>"); out.write("</html>"); out.close(); } private void form(String contextPath, HttpServletResponse resp) throws IOException { resp.setContentType("text/html;charset=utf-8"); PrintWriter out = resp.getWriter(); String href1 = contextPath + LIST; out.write("<html>"); out.write("<head><title>form</title></thead>"); out.write("<body>"); out.write("<b><a href='" + href1 + "'>点击</a>返回文件列表</b>"); out.write( "<form action='handle' method='post' enctype='multipart/form-data' style='margin-top:20px;'>"); out.write("<input name='file' type='file'/><br>"); out.write("<input type='submit' value='上传'/><br>"); out.write("</form>"); out.write("</body>"); out.write("</html>"); out.close(); } private void notfound(String contextPath, HttpServletResponse resp) throws IOException { resp.setContentType("text/html;charset=utf-8"); PrintWriter out = resp.getWriter(); String href1 = contextPath + LIST; out.write("<html><body><b>操作失败！文件不存在或文件已经被删除！<a href='" + href1 + "'>点击</a>返回文件列表</b></body></html>"); out.close(); } private void download(File f, HttpServletResponse resp) throws IOException { String fn = f.getName(); String fileName = fn.substring(0, fn.lastIndexOf("_")); System.out.println("fileName:" + fileName); resp.reset(); resp.setContentType("application/octet-stream"); String encodingFilename = new String(fileName.getBytes("GBK"), "ISO8859-1"); System.out.println("encodingFilename:" + encodingFilename); resp.setHeader("content-disposition", "attachment;filename=" + encodingFilename); InputStream in = new FileInputStream(f); OutputStream out = resp.getOutputStream(); byte[] b = new byte[1024]; int n = 0; while ((n = in.read(b)) != -1) { out.write(b, 0, n); } out.flush(); in.close(); out.close(); } private void list(String contextPath, String basePath, HttpServletResponse resp) throws IOException { String href_u = contextPath + FORM; resp.setContentType("text/html;charset=utf-8"); PrintWriter out = resp.getWriter(); out.write("<html>"); out.write("<head><title>list</title></thead>"); out.write("<body>"); out.write("<b>我要<a href='" + href_u + "'>上传</a></b><br>"); out.write( "<table border='1' style='border-collapse:collapse;width:100%;margin-top:20px;'>"); out.write("<thead>"); out.write("<tr>"); out.write("<th>序号</th><th>文件名</th><th>操作</th>"); out.write("</tr>"); out.write("</thead>"); out.write("<tbody>"); File file = new File(basePath); File[] list = file.listFiles(); System.out .println("basePath:" + basePath + "/tlist.size:" + list.length); int len = list.length; int no = 1; for (int i = 0; i < len; i++) { File f = list[i]; System.out.println(i + "/t" + f.getName()); String fn = f.getName(); if (f.isFile() && fn.lastIndexOf("_") > -1) { String filename = fn.substring(0, fn.lastIndexOf("_")); String id = fn.substring(fn.lastIndexOf("_")); String href1 = contextPath + DOWNLOAD + "?id=" + id; String href2 = contextPath + DELETE + "?id=" + id; StringBuilder sb = new StringBuilder(); sb.append("<tr>"); sb.append("<td>"); sb.append(no++); sb.append("</td>"); sb.append("<td>"); sb.append(filename); sb.append("</td>"); sb.append("<td>"); sb.append("<a href='"); sb.append(href1); sb.append("'>下载</a> <a href='"); sb.append(href2); sb.append("' onclick='return confirm(/"您确定要删除吗？/");'>删除</a>"); sb.append("</td>"); sb.append("</tr>"); out.write(sb.toString()); } } out.write("</tbody>"); out.write("</table>"); out.write("</body>"); out.write("</html>"); out.close(); } public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { System.out.println("doGet..."); execute(req, resp); } public void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { System.out.println("doPost..."); execute(req, resp); } private String getSuffix() { Date date = new Date(); SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmssSSS"); String suffix = sdf.format(date); return suffix; }}其实UploadService类可以直接实现service方法，而不用实现doGet、doPost方法。
以上servlet我也不想多解释什么，自己看代码吧。
五、效果图
1.项目结构图
2.404页面
/*会匹配所有包括空字符，所以图片中的路径会匹配，在UploadService中的if判断中出现在else中，因为此时的action是空字符。
3.文件列表页面
4.上传表单页面
5.下载
6.删除
7.文件找不到，如果你点删除时，文件在服务器上已经不存在，那么会进入此页面
8.打包的源码工程和war包
其中z-upload是eclipse源码工程，z-upload.war是打好的war包
全工程就两个jar包，一个web.xml和一个servlet类，可以自己从文章中拷贝过去测试一下，如果是懒人，可以下载
http://download.csdn.net/detail/yunsyz/9569680，特别提醒，下载要1分哦。
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持武林网。