在java项目中使用Demo如何实现一个文件上传功能？相信很多没有经验的人对此束手无策，为此本文总结了问题出现的原因和解决方法，通过这篇文章希望你能解决这个问题。
说到文件上传我们要做到：
1.引入两个包：commons-fileupload-1.2.1.jar和commons-io-1.3.2.jar
2.将form改为上传文件模式：enctype="multipart/form-data"
3.开始编写相关代码
这里会用到几个关键的类：磁盘文件工厂DiskFileItemFactory ； 创建servlet文件上传类：ServletFileUpload
还有几个重要的方法：DiskFileItemFactory类用于将以临时文件形式保存在磁盘上的存放目录的方法setRepository；
ServletFileUpload类得到表单中所有的数据，得到form表单中所有的元素方法：parseRequest
下面看具体代码：
说明以这种方式上传文件是保存在服务器端的！
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();//实例化磁盘被文件列表工厂
String path = request.getRealPath("/upload");//得到上传文件的存放目录
sf.setRepository(new File(path));//设置文件存放目录
sf.setSizeThreshold(1024*1024);//设置文件上传小于1M放在内存中
String rename = "";//文件新生成的文件名
String fileName = "";//文件原名称
String name = "";//普通field字段
//从工厂得到servletupload文件上传类
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{
//获得文件名称
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("文件名称"+fileName);
System.out.println("修改后生成的文件名称"+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页面：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>文件测试界面</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">
名称：<input name="name" /> <br>
图片：<input name="img" type="file"/><br>
<input type="submit" value="提交" />
<input type="reset" value="重置" />
</form>
</div>
</body>
</html>ok.jsp页面：
<body> <h2 align="center">上传文件成功!</h2> </body>
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