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

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