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java文件上传Demo(必看篇)

2019年07月22日  | 移动技术网IT编程  | 我要评论

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>
  <h1 align="center">上传文件成功!</h1>
 </body>

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移动技术网。

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