說到文件上傳我們要做到：
1.引入兩個包：commons-fileupload-1.2.1.jar和commons-io-1.3.2.jar
2.將form改為上傳文件模式：enctype="multipart/form-data"
3.開始編寫相關代碼
這裡會用到幾個關鍵的類：磁盤文件工廠DiskFileItemFactory ； 創建servlet文件上傳類：ServletFileUpload
還有幾個重要的方法：DiskFileItemFactory類用於將以臨時文件形式保存在磁盤上的存放目錄的方法setRepository；
ServletFileUpload類得到表單中所有的數據，得到form表單中所有的元素方法：parseRequest
下面看具體代碼：
說明以這種方式上傳文件是保存在服務器端的！
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
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.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.io.FileUtils;
public class UploadServlet extends HttpServlet {
/**
* Constructor of the object.
*/
public UploadServlet() {
super();
}
/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}
/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}
/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
DiskFileItemFactory sf= new DiskFileItemFactory();//實例化磁盤被文件列表工廠
String path = request.getRealPath("/upload");//得到上傳文件的存放目錄
sf.setRepository(new File(path));//設置文件存放目錄
sf.setSizeThreshold(1024*1024);//設置文件上傳小於1M放在內存中
String rename = "";//文件新生成的文件名
String fileName = "";//文件原名稱
String name = "";//普通field字段
//從工廠得到servletupload文件上傳類
ServletFileUpload sfu = new ServletFileUpload(sf);
try {
List<FileItem> lst = sfu.parseRequest(request);//得到request中所有的元素
for (FileItem fileItem : lst) {
if(fileItem.isFormField()){
if("name".equals(fileItem.getFieldName())){
name = fileItem.getString("UTF-8");
}
}else{
//獲得文件名稱
fileName = fileItem.getName();
fileName = fileName.substring(fileName.lastIndexOf("\\")+1);
String houzhui = fileName.substring(fileName.lastIndexOf("."));
rename = UUID.randomUUID()+houzhui;
fileItem.write(new File(path, rename));
}
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("普通字段"+name);
System.out.println("文件名稱"+fileName);
System.out.println("修改後生成的文件名稱"+rename);
response.sendRedirect("ok.jsp");
out.flush();
out.close();
}
/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
}
}
index.jsp頁面：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>文件測試界面</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">
</head>
<body>
<div align="center">
<form action="UploadServlet" enctype="multipart/form-data" method="post">
名稱：<input name="name" /> <br>
圖片：<input name="img" type="file"/><br>
<input type="submit" value="提交" />
<input type="reset" value="重置" />
</form>
</div>
</body>
</html>
ok.jsp頁面：
<body> <h1 align="center">上傳文件成功!</h1> </body>
實現效果就不截圖了，有需要自己那過去用！
以上這篇java文件上傳Demo(必看篇)就是小編分享給大家的全部內容了，希望能給大家一個參考，也希望大家多多支持。
