Apache commons fileupload文件上传实例讲解

文件上传的方法主要目前有两个常用的，一个是SmartUpload，一个是Apache的Commons fileupload.

我们这里主要介绍下第二个的用法，首先要上传文件，注意几个问题：

1 form表单内，要添加空间<input type="file" name="myfile">

2 form表单的内容格式要定义成multipart/form-data格式

3 需要类库：1 commons-io.jar 2commons-fileupload-1.3.1.jar

接下来我们看下用法。

首先阅读Apache commons fileupload的官方文档可以发现下面几个常用的函数：

1 创建文件解析对象

DiskFileUpload diskFileUpload = new DiskFileUpload();

2 进行文件解析后放在List中，因为这个类库支持多个文件上传，因此把结果会存在List中。

List<FileItem> list = diskFileUpload.parseRequest(request);

3 获取上传文件，进行分析（不是必须）

File remoteFile = new File(new String(fileItem.getName().getBytes(),"UTF-8"));

4 创建新对象，进行流拷贝

file1 = new File(this.getServletContext().getRealPath("attachment"),remoteFile.getName());
           file1.getParentFile().mkdirs();
           file1.createNewFile();

InputStream ins = fileItem.getInputStream();
           OutputStream ous = new FileOutputStream(file1);

try{
             byte[] buffer = new byte[1024];
             int len = 0;
             while((len = ins.read(buffer)) > -1)
               ous.write(buffer,0,len);
             out.println("以保存文件"+file1.getAbsolutePath()+"<br/>");
           }finally{
             ous.close();
             ins.close();
           }

这样我们就完成了文件的上传。

fileUpload.html

<form action="servlet/UploadServlet" method="post" enctype="multipart/form-data">
   <div align="center">
     <fieldset style="width:80％">
       <legend>上传文件</legend><br/>
         <div align="left">上传文件1</div>
         <div align="left">
           <input type="file" name="file1"/>
         </div>
         <div align="left">上传文件2</div>
         <div align="left">
           <input type="file" name="file2"/>
         </div>
         <div>
           <div align='left'>上传文件说明1</div>
           <div align='left'><input type="text" name="description1"/></div>
         </div>
         <div>
           <div align='left'>上传文件说明2</div>
           <div align='left'><input type="text" name="description2"/></div>
         </div>
         <div>
           <div align='left'>
             <input type='submit' value="上传文件"/>
           </div>
         </div>
     </fieldset>
   </div>
 </form>

web.xml

<servlet>
 <servlet-name>UploadServlet</servlet-name>
 <servlet-class>com.test.hello.UploadServlet</servlet-class>
</servlet>
<servlet-mapping>
 <servlet-name>UploadServlet</servlet-name>
 <url-pattern>/servlet/UploadServlet</url-pattern>
</servlet-mapping>

UploadServlet.java

package com.test.hello;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.DiskFileUpload;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;

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 {

response.setCharacterEncoding("UTF-8");
   response.getWriter().println("请以POST方式上传文件");
 }

/**
  * 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
  */
 @SuppressWarnings({ "unchecked", "deprecation" })
 public void doPost(HttpServletRequest request, HttpServletResponse response)
     throws ServletException, IOException {
   File file1 = null,file2=null;
   String description1 = null,description2 = null;
   response.setCharacterEncoding("UTF-8");
   request.setCharacterEncoding("UTF-8");
   response.setContentType("text/html");
   PrintWriter out = response.getWriter();

DiskFileUpload diskFileUpload = new DiskFileUpload();
   try{
     List<FileItem> list = diskFileUpload.parseRequest(request);

out.println("遍历所有的FileItem...<br/>");
     for(FileItem fileItem : list){
       if(fileItem.isFormField()){
         if("description1".equals(fileItem.getFieldName())){
           out.println("遍历到description1 ... <br/>");
           description1 = new String(fileItem.getString().getBytes(),"UTF-8");
         }
         if("description2".equals(fileItem.getFieldName())){
           out.println("遍历到description2 ... <br/>");
           description2 = new String(fileItem.getString().getBytes(),"UTF-8");
         }
       }else{
         if("file1".equals(fileItem.getFieldName())){
           File remoteFile = new File(new String(fileItem.getName().getBytes(),"UTF-8"));
           out.println("遍历到file1...<br/>");
           out.println("客户端文件位置："+remoteFile.getAbsolutePath()+"<br/>");

file1 = new File(this.getServletContext().getRealPath("attachment"),remoteFile.getName());
           file1.getParentFile().mkdirs();
           file1.createNewFile();

InputStream ins = fileItem.getInputStream();
           OutputStream ous = new FileOutputStream(file1);

try{
             byte[] buffer = new byte[1024];
             int len = 0;
             while((len = ins.read(buffer)) > -1)
               ous.write(buffer,0,len);
             out.println("以保存文件"+file1.getAbsolutePath()+"<br/>");
           }finally{
             ous.close();
             ins.close();
           }
         }
         if("file2".equals(fileItem.getFieldName())){
           File remoteFile = new File(new String(fileItem.getName().getBytes(),"UTF-8"));
           out.println("遍历到file2...<br/>");
           out.println("客户端文件位置："+remoteFile.getAbsolutePath()+"<br/>");

file2 = new File(this.getServletContext().getRealPath("attachment"),remoteFile.getName());
           file2.getParentFile().mkdirs();
           file2.createNewFile();

InputStream ins = fileItem.getInputStream();
           OutputStream ous = new FileOutputStream(file2);

try{
             byte[] buffer = new byte[1024];
             int len = 0;
             while((len = ins.read(buffer)) > -1)
               ous.write(buffer,0,len);
             out.println("以保存文件"+file2.getAbsolutePath()+"<br/>");
           }finally{
             ous.close();
             ins.close();
           }
         }
       }
       out.println("Request 解析完毕<br/><br/>");
     }
   }catch(FileUploadException e){}

out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
   out.println("<HTML>");
   out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");
   out.println(" <BODY>");

if(file1 != null){
     out.println("<div>");
     out.println(" <div align='left'>file1;</div>");
     out.println(" <div align='left'><a href='"+request.getContextPath()+"/attachment/"+
         file1.getName()+"'target=_blank>"+file1.getName()+"</a>");
     out.println("</div>");
     out.println("</div>");
   }
   if(file2 != null){
     out.println("<div>");
     out.println(" <div align='left'>file2;</div>");
     out.println(" <div align='left'><a href='"+request.getContextPath()+"/attachment/"+
         file2.getName()+"'target=_blank>"+file2.getName()+"</a>");
     out.println("</div>");
     out.println("</div>");
   }
   out.println("<div>");
   out.println(" <div align='left'>description1:</div>");
   out.println(" <div align='left'>");
   out.println(description1);
   out.println("</div>");
   out.println("</div>");

out.println("<div>");
   out.println(" <div align='left'>description2:</div>");
   out.println(" <div align='left'>");
   out.println(description2);
   out.println("</div>");
   out.println("</div>");

out.println(" </BODY>");
   out.println("</HTML>");
   out.flush();
   out.close();
 }

/**
  * Initialization of the servlet. <br>
  *
  * @throws ServletException if an error occurs
  */
 public void init() throws ServletException {
   // Put your code here
 }

}

运行示例