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 {
 
  
  public UploadServlet() {
    super();
  }
 
  
  public void destroy() {
    super.destroy(); // Just puts "destroy" string in log
    // Put your code here
  }
 
  
  public void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
 
    this.doPost(request, response);
  }
 
  
  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 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();
  }
 
  
  public void init() throws ServletException {
    // Put your code here
  }
 
}

index.jsp页面：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>


   
  
  
  
    
  
  
 
 
  
  
  
 

ok.jsp页面：

  
上传文件成功!
 

实现效果就不截图了，有需要自己那过去用！

以上这篇java文件上传Demo(必看篇)就是小编分享给大家的全部内容了，希望能给大家一个参考，也希望大家多多支持考高分网。