1.准备工作,下载apache的IO包和fileupload包,并将它们拷贝到web-inf下的lib目录里面,注意要在WebRoot下建一个upload的目录,用来保存上传的文件
2. 编写类FileUploadServlet
package org.liky.fileupload; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.util.List; import javax.servlet.RequestDispatcher; import javax.servlet.ServletConfig; 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 FileUploadServlet extends HttpServlet { private static final long serialVersionUID = 8088769669368270752L; // 如果文件的大小超过这个数值，将直接写入磁盘，而不会放在内存缓冲区 private int threshold = 0; // 服务器端临时文件上传目录 private String repository; // 单个上传文件大小的最大值 private long fileSizeMax; @SuppressWarnings("unchecked") @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); response.setCharacterEncoding("UTF-8"); DiskFileItemFactory factory = new DiskFileItemFactory(); // 设置内存缓冲区的大小 factory.setSizeThreshold(threshold); // 设置临时文件上传目录 factory.setRepository(new File(repository)); // 创建文件上出的实例 ServletFileUpload upload = new ServletFileUpload(factory); // 设置单个上传文件大小的最大值 upload.setFileSizeMax(fileSizeMax); try { List<FileItem> fileItems = upload.parseRequest(request); for (FileItem fileItem : fileItems) { if (fileItem.isFormField()) { // 获得普通表单项的名字 String name = fileItem.getFieldName(); // 获得普通表单项的值 String value = fileItem.getString(); System.out.println(name + ": " + value); // 将普通表单项放入request请求中继续向前转发,以进一步处理 request.setAttribute(name, value); } else { writeFiles(fileItem, request); } } } catch (FileUploadException e) { e.printStackTrace(); } RequestDispatcher formHandler = request .getRequestDispatcher("/formHandler.do"); if (null != formHandler) { formHandler.forward(request, response); System.out.println("****************** FormHandler *****************"); } else { throw new ServletException("Sorry, formHandler.do not found!"); } } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } /** * 将文件写入磁盘,注意为了提高效率, 我们没有直接调用FileItem.get()来读取文件内容, * 因为如果文件非常大的话,网络将承受不了,所以使用了缓冲区来读取, 如果上传的文件很小,则大可以使用这个方法 * * @param fileItem */ @SuppressWarnings("deprecation") private void writeFiles(FileItem fileItem, HttpServletRequest request) throws IOException { // 处理不同的浏览器上传文件时,文件名和路径的问题,有的浏览器只会显示文件名 // 但是有的浏览器却会将完整路径也加上,因此需要处理 String fileNameString = fileItem.getName(); int start = fileNameString.indexOf("//"); String fileName = fileNameString.substring(start + 1); // 获得当前web应用的根路径 String parent = request.getRealPath(repository); // 构造一个File对象,规则是当前web应用的根路径加上文件名 File file = new File(parent, fileName); // 设输出流一个缓冲区 byte[] buffer = new byte[1024]; // 获得实际能够有效读取的字节数组的长度 int length = 0; // 获得FileItem的文件输入流 InputStream is = fileItem.getInputStream(); // 构造一个文件输出流 FileOutputStream fos = new FileOutputStream(file); // 将字节流按顺序读入缓冲区,如果已经读到了字节输入流的末尾, // 也就是length小于或等于0时,读取结束 while ((length = is.read(buffer)) > 0) { fos.write(buffer, 0, length); } // 记得关闭输入和输出流 fos.close(); is.close(); } /** * 设置servlet的初始化参数 */ @Override public void init(ServletConfig config) throws ServletException { String thresholdParam = config.getInitParameter("threshold"); String repositoryParam = config.getInitParameter("repository"); String fileSizeMaxParam = config.getInitParameter("fileSizeMax"); if (null != thresholdParam) { this.threshold = Integer.parseInt(thresholdParam); } if (null != repositoryParam) { this.repository = repositoryParam; } if (null != repositoryParam) { this.fileSizeMax = Integer.parseInt(fileSizeMaxParam); } } }
3.编写类FormHandlerServlet
package org.liky.fileupload; import java.io.IOException; import javax.servlet.RequestDispatcher; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class FormHandlerServlet extends HttpServlet { private static final long serialVersionUID = -3433917547449179227L; public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); String username = request.getAttribute("username").toString(); String password = request.getAttribute("password").toString(); String ageParam = request.getAttribute("age").toString(); User user = new User(); user.setUsername(username); user.setPassword(password); if (null != ageParam) { user.setAge(Integer.parseInt(ageParam)); } System.out.println(user.getUsername()); System.out.println(user.getPassword()); System.out.println(user.getAge()); request.setAttribute("user", user); RequestDispatcher show = request.getRequestDispatcher("show.jsp"); if (null != show) { show.forward(request, response); } else { response.sendRedirect("/index.jsp"); } } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request,response); } }
4.编写类User
package org.liky.fileupload; public class User { private String username; private String password; private int age; public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } }
5.文件上传的JSP页面index.jsp
<%@ page language="java" contentType="text/html;charset=UTF-8"%> <%request.setCharacterEncoding("UTF-8"); %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>上传文件</title> </head> <body> <form action="fileUpload.do" name="FileForm" method="post" enctype="multipart/form-data"> 姓名：<input type="text" name="username"><br> 年龄：<input type="text" name="age"><br> 密码：<input type="password" name="password"><br> 文件：<input type="file" name="file"><br> <input type="submit" value="提交"> </form> </body> </html>
6.查看用户信息的JSP页面show.jsp
<%@ page language="java" contentType="text/html;charset=UTF-8"%> <%@ page import="org.liky.fileupload.User" %> <%request.setCharacterEncoding("UTF-8");%> <% User user = (User)request.getAttribute("user"); %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>显示用户信息</title> </head> <body> <h2>显示用户信息</h2> 姓名:<%=user.getUsername()%><br> 密码:<%=user.getPassword()%><br> 年龄:<%=user.getAge()%><br> </body> </html>
7.web.xml文件的配置
<?xml version="1.0" encoding="UTF-8"?> <web-app version="2.5" 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_2_5.xsd"> <servlet> <servlet-name>FileUploadServlet</servlet-name> <servlet-class> org.liky.fileupload.FileUploadServlet </servlet-class> <init-param> <!-- 上传文件内存缓冲区的大小,大于这个值将直接写入临时磁盘存储目录 --> <param-name>threshold</param-name> <param-value>1048576</param-value> </init-param> <init-param> <!-- 服务器端上传文件的临时磁盘存储目录 --> <param-name>repository</param-name> <param-value>/upload</param-value> </init-param> <init-param> <!-- 允许单个上传文件大小的最大值 --> <param-name>fileSizeMax</param-name> <param-value>10485760</param-value> </init-param> </servlet> <servlet> <servlet-name>FormHandlerServlet</servlet-name> <servlet-class>org.liky.fileupload.FormHandlerServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>FileUploadServlet</servlet-name> <url-pattern>/fileUpload.do</url-pattern> </servlet-mapping> <servlet-mapping> <servlet-name>FormHandlerServlet</servlet-name> <url-pattern>/formHandler.do</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>
