fileupload 为什么InputStream getInputStream()方法无法获取临时文件里的文件

Question

package com.wgh.servlet;

import java.io.*;
import java.util.*;

import org.apache.commons.fileupload.*;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

import javax.servlet.*;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
@WebServlet("/UploadServlet")
public class UploadServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    doPost(request,response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    String uploadPath=getServletContext().getRealPath("/")+"upload";          //定义上传文件的地址 
    System.out.println(uploadPath);

    File folder = new File(uploadPath);
    if(!folder.exists())
        folder.mkdirs();
    String message=null;
    String content=null;
    String dtme=null;
    if(ServletFileUpload.isMultipartContent(request)){  //判断是否获取的是文件

        System.out.print("是文件");
        DiskFileItemFactory disk=new DiskFileItemFactory();
        disk.setSizeThreshold(20*1024);                 //设置内存可存字节数
        disk.setRepository(disk.getRepository());       //设置临时文件目录
        ServletFileUpload up=new ServletFileUpload(disk);
        int maxsize=2*1024*1024;
        List list=null;
        try{
            list=up.parseRequest(request);              //获取上传列表
        }
        catch(Exception e){
            e.printStackTrace();
        }
        Iterator i=list.iterator();                     //创建列表的迭代器
        while(i.hasNext()){
            FileItem fm=(FileItem)i.next();             //遍历列表

            if(!fm.isFormField()){
                String filePath = fm.getName(); //获取文件全路径名
                String fileName="";
                int startIndex = filePath.lastIndexOf("\\");
                if(startIndex!=-1){                     //对文件名进行截取
                    fileName = filePath.substring(startIndex+1);
                }else{
                    fileName=filePath;
                }
                if(fm.getSize()>maxsize){
                    message="文件太大了，不要超过2MB";
                    break;
                }
                String fileSize=new Long(fm.getSize()).toString();
                if((fileName==null)||(fileName.equals(""))&&(fileSize.equals("0"))){
                    message="文件名不能为空，文件大小也不能为零！";
                    break;
                }
                File saveFile=new File(uploadPath,fileName);
                System.out.println(uploadPath);
                try{
                    fm.write(saveFile);                //向文件中写入数据
                    message="文件上传成功！";
                    <span style="color: #FF0000;">InputStream  inStream=fm.getInputStream();</span>//这行报错
                    System.out.println("hhhhhh");
                }
                catch(Exception e1){
                    e1.printStackTrace();
                }
            }
            else{
                String foename=fm.getFieldName();     //获取表单元素名
                String con=fm.getString("UTF-8");       //获取表单内容，注意编码方式
                //表单元素
                if(foename.equals("upDe")){
                     content = con;
                     System.out.println("ok1");
                }
                else if(foename.equals("uptime")){
                     dtme = con;
                     System.out.println("ok2");
                }
            }
        }
    }
    else
    {
        System.out.println("不是文件");
    }
    request.setAttribute("result",message);
    request.setAttribute("upDe",content);
    request.setAttribute("dtme",dtme);
    RequestDispatcher rd=request.getRequestDispatcher("message.jsp");
    rd.forward(request, response);
}

public void init(ServletConfig config) throws ServletException {
    super.init(config);
}

}

当文件超过20k时就会报错，

java.io.FileNotFoundException: C:\Users\wsn\AppData\Local\Temp\upload__1c3b5e7d_1476c27ed8a__7fff_00000006.tmp (系统找不到指定的文件。)

到底是怎样读取临时文件的文件流呢

这是index.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML>

通过commons-fileupload获取其他表单元素
<br> table{<br> font-size: 13px;</p> <pre><code> } input{ font-size: 12px; } &lt;/style&gt; </code></pre> <p></head></p> <p><body><br> &lt;%! <br> Date now=new Date();<br> String form=String.format(&quot;%tF&quot;,now);<br> %&gt;<br> <form method="post" action="UploadServlet" enctype="multipart/form-data"><br> <table background="bg.jpg" width="400" height="200"><br> <tr><br> <td height="20" colspan="2"></td><br><br> </tr><br> <tr><br> <td align="center" colspan="2">【应用Commons-FileUpload获取其他表单元素】</td><br><br> </tr><br> <tr><br> <td height="20" colspan="2"></td><br><br> </tr><br> <tr><br> <td align="right">选择文件：</td><br><br> <td > <input type="file" name="file1"></td><br> </tr><br> <tr><br> <td align="right">文件描述：</td><br> <td > <input type="text" name="upDe" ></td><br> </tr><br> <tr><br> <td align="right">上传时间：</td><br> <td > <input type="text" name="uptime" value=<%=form%>&gt;</td><br> </tr><br> <tr><br> <td align="center"></td><br> <td > <input type="submit" value="开始上传"></td></p> <pre><code>&lt;/tr&gt; &lt;tr&gt; &lt;td height=&quot;40&quot; colspan=&quot;2&quot;&gt;&lt;/td&gt; &lt;/tr&gt; &lt;/table&gt; &lt;/form&gt; </code></pre> <p></body><br> </html></p>

Answer 1

我在机器上试了。

1、你的这一行报错，InputStream inStream=fm.getInputStream();读不到文件，是应为fm是临时文件，上传成功后已经不存在了，所以你试图读取时报找不到文件的错误。

2、如果你想读文件流 ，可以这样读[code="java"]InputStream inStream = new FileInputStream(saveFile);[/code]