Apache commons fileupload文件上传实例讲解

POOPE

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
复制代码 代码如下:

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。
复制代码 代码如下:

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

3 获取上传文件，进行分析（不是必须）
复制代码 代码如下:

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>
     <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

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