文件上传之Apache commons fileupload使用

　　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

　　接下来我们看下他的用法。

　　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="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