web文件上传也是一种POST方式，特别之处在于，需设置FORM的enctype属性为multipart/form-data。
并且需要使用文件域。
servlet的代码比较关键是这几句：
// 使用 DiskFileUpload 对象解析 request
DiskFileUpload diskFileUpload = new DiskFileUpload();
// 将 解析的结果 放置在 List 中
List<FileItem> list = diskFileUpload.parseRequest(request);
package com.servlet; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.io.PrintWriter; import java.net.URLEncoder; 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.DiskFileUpload; import org.apache.commons.fileupload.FileItem; import org.apache.commons.fileupload.FileUploadException; @SuppressWarnings("deprecation") public class UploadServlet extends HttpServlet { private static final long serialVersionUID = 7523024737218332088L; public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setCharacterEncoding("UTF-8"); response.getWriter().println("请以 POST 方式上传文件"); } @SuppressWarnings("unchecked") public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { File file1 = null, file2 = null; String description1 = null, description2 = null; response.setCharacterEncoding("UTF-8"); response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">"); out.println("<HTML>"); out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>"); out.println(" <link rel='stylesheet' type='text/css' href='../css/style.css'>"); out.println(" <BODY>"); out.println("<div align=center><br/>"); out.println("<fieldset style='90%'><legend>上传文件</legend><br/>"); out.println(" <div class='line'>"); out.println(" <div align='left' class='leftDiv'>上传日志：</div>"); out.println(" <div align='left' class='rightDiv'>"); // 使用 DiskFileUpload 对象解析 request DiskFileUpload diskFileUpload = new DiskFileUpload(); try { // 将 解析的结果 放置在 List 中 List<FileItem> list = diskFileUpload.parseRequest(request); out.println("遍历所有的 FileItem ... <br/>"); // 遍历 list 中所有的 FileItem for(FileItem fileItem : list){ if(fileItem.isFormField()){ // 如果是 文本域 if("description1".equals(fileItem.getFieldName())){ // 如果该 FileItem 名称为 description1 out.println("遍历到 description1 ... <br/>"); description1 = new String(fileItem.getString().getBytes(), "UTF-8"); } if("description2".equals(fileItem.getFieldName())){ // 如果该 FileItem 名称为 description2 out.println("遍历到 description2 ... <br/>"); description2 = new String(fileItem.getString().getBytes(), "UTF-8"); } } else{ // 否则，为文件域 if("file1".equals(fileItem.getFieldName())){ // 客户端文件路径构建的 File 对象 File remoteFile = new File(new String(fileItem.getName().getBytes(), "UTF-8")); out.println("遍历到 file1 ... <br/>"); out.println("客户端文件位置: " + remoteFile.getAbsolutePath() + "<br/>"); // 服务器端文件，放在 upload 文件夹下 file1 = new File(this.getServletContext().getRealPath("attachment"), remoteFile.getName()); file1.getParentFile().mkdirs(); file1.createNewFile(); // 写文件，将 FileItem 的文件内容写到文件中 InputStream ins = fileItem.getInputStream(); OutputStream ous = new FileOutputStream(file1); try{ byte[] buffer = new byte[1024]; int len = 0; while((len=ins.read(buffer)) > -1) ous.write(buffer, 0, len); out.println("已保存文件" + file1.getAbsolutePath() + "<br/>"); }finally{ ous.close(); ins.close(); } } if("file2".equals(fileItem.getFieldName())){ // 客户端文件路径构建的 File 对象 File remoteFile = new File(new String(fileItem.getName().getBytes(), "UTF-8")); out.println("遍历到 file2 ... <br/>"); out.println("客户端文件位置: " + remoteFile.getAbsolutePath() + "<br/>"); // 服务器端文件，放在 upload 文件夹下 file2 = new File(this.getServletContext().getRealPath("attachment"), remoteFile.getName()); file2.getParentFile().mkdirs(); file2.createNewFile(); // 写文件，将 FileItem 的文件内容写到文件中 InputStream ins = fileItem.getInputStream(); OutputStream ous = new FileOutputStream(file2); try{ byte[] buffer = new byte[1024]; int len = 0; while((len=ins.read(buffer)) > -1) ous.write(buffer, 0, len); out.println("已保存文件" + file2.getAbsolutePath() + "<br/>"); }finally{ ous.close(); ins.close(); } } } } out.println("Request 解析完毕"); } catch (FileUploadException e) { // TODO Auto-generated catch block e.printStackTrace(); } out.println(" </div>"); out.println(" </div>"); if(file1 != null){ out.println(" <div class='line'>"); out.println(" <div align='left' class='leftDiv'>file1：</div>"); out.println(" <div align='left' class='rightDiv'>"); out.println(" <a href='" + request.getContextPath() + "/attachment/" + file1.getName() + "' target=_blank>" + file1.getName() + "</a>" ); out.println(" </div>"); out.println(" </div>"); } if(file2 != null){ out.println(" <div class='line'>"); out.println(" <div align='left' class='leftDiv'>file2：</div>"); out.println(" <div align='left' class='rightDiv'>"); out.println(" <a href='" + request.getContextPath() + "/attachment/" + URLEncoder.encode(file2.getName(), "UTF-8") + "' target=_blank>" + file2.getName() + "</a>" ); out.println(" </div>"); out.println(" </div>"); } out.println(" <div class='line'>"); out.println(" <div align='left' class='leftDiv'>description1：</div>"); out.println(" <div align='left' class='rightDiv'>"); out.println(description1); out.println(" </div>"); out.println(" </div>"); out.println(" <div class='line'>"); out.println(" <div align='left' class='leftDiv'>description2：</div>"); out.println(" <div align='left' class='rightDiv'>"); out.println(description2); out.println(" </div>"); out.println(" </div>"); out.println("</fieldset></div>"); out.println(" </BODY>"); out.println("</HTML>"); out.flush(); out.close(); } }
upload.html
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>上传文件</title> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="this is my page"> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> <link rel="stylesheet" type="text/css" href="css/style.css"> </head> <body> <form action="servlet/UploadServlet" method="post" enctype="multipart/form-data"> <div align="center"><br/> <fieldset style="90%"> <legend>上传文件</legend><br/> <div class='line'> <div align='left' class="leftDiv">上传文件一</div> <div align='left' class="rightDiv"> <input type="file" name="file1" class="text"> </div> </div> <div class='line'> <div align='left' class="leftDiv">上传文件二</div> <div align='left' class="rightDiv"> <input type="file" name="file2" class="text"> </div> </div> <div class='line'> <div align='left' class="leftDiv">上传文件说明一</div> <div align='left' class="rightDiv"><input type="text" name="description1" class="text"></div> </div> <div class='line'> <div align='left' class="leftDiv">上传文件说明二</div> <div align='left' class="rightDiv"><input type="text" name="description2" class="text"></div> </div> <div class='line'> <div align='left' class="leftDiv"></div> <div align='left' class="rightDiv"><br/> <input type="submit" value=" 上传文件 " class="button"> </div> </div> </fieldset> </div> </form> </body> </html>
