文件上传的时候文件变小了还打不开，，求解释啊。。大神进 - 黑马程序员技术交流社区

package zhiwei.deng.web.servlet.util;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.List;
import java.util.UUID;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import zhiwei.deng.web.servlet.domain.User;
import zhiwei.deng.web.servlet.exception.NoFileUpException;
import zhiwei.deng.web.servlet.exception.UpFileSizeException;
import zhiwei.deng.web.servlet.exception.UpFileTypeException;
public class UploadUtil {
//设置文件上传的临时目录
public static String tempPath = "/WEB-INF/temp";
public static String uploadPath = "/WEB-INF/upload";
//
public static void doSave(User user,String uploadPath) throws Exception{
//得到上传的文件
List<FileItem> fileItemList = user.getFileItemList();
for(FileItem fileItem : fileItemList){
BufferedInputStream bis = new BufferedInputStream(fileItem.getInputStream());
//取得uuid文件名
String realFileName = fileItem.getName();
realFileName = UploadUtil.realFileName(realFileName);
String uuidFileName = UploadUtil.makeUuidFileName(realFileName);
//取得uuid文件路径
String uuidFilePath = UploadUtil.makeUuidFilePath(uploadPath, realFileName);
//复制
UploadUtil.doSave(bis, uuidFilePath, uuidFileName);
//删除临时目录
fileItem.delete();
}
}
//将上传文件封装到一个javabean中
public static User doUpload(HttpServletRequest request) throws Exception{
User user = new User();
//得到一个文件上传的工厂
DiskFileItemFactory factory = new DiskFileItemFactory();
//设置缓存的大小，默认是10K
factory.setSizeThreshold(100*1024);
String tempPath = request.getSession().getServletContext().getRealPath(UploadUtil.tempPath);
factory.setRepository(new File(tempPath));
//文件上传的核心
ServletFileUpload upload = new ServletFileUpload(factory);
//设置文件上传的编码方式
upload.setHeaderEncoding("utf-8");
//判断上传的是否是MIME协议
boolean flag = upload.isMultipartContent(request);
if(flag){
//如果是MIME协议的话
List<FileItem> list = upload.parseRequest(request);
List<FileItem> fileItemList = new ArrayList<FileItem>();
for(FileItem fileItem : list){
//判断是否是普通(窗体)字段,只有两种情况，要不然就是上传字段
if(fileItem.isFormField()){
//如果是普通字段
String fieldName = fileItem.getFieldName();
String fieldValue = fileItem.getString("utf-8");
//把用户的名称放进javaBean中
user.setUsername(fieldValue);
}else{
//必定是上传字段了
//没有上传文件
if(fileItem.getSize()==0){
throw new NoFileUpException();
}
if(!UploadUtil.realFileName(fileItem.getName()).endsWith(".jpg")){
fileItem.delete();
throw new UpFileTypeException();
}
if(fileItem.getSize()> 200 * 1024){
fileItem.delete();
throw new UpFileSizeException();
}
//user.setFileItem(fileItem);
//fileItemList.add(fileItem);
user.getFileItemList().add(fileItem);
}
}
}else{
throw new ServletException();
}
return user;
}
//复制文件
public static void doSave(BufferedInputStream bis,String uuidFilePath,String uuidFileName){
BufferedOutputStream bos = null;
try {
bos = new BufferedOutputStream(new FileOutputStream(uuidFilePath+"/"+uuidFileName));
int len=0;
byte[] buf = new byte[1024];
while((len=bis.read())>0){
bos.write(buf, 0, len);
}
}catch(Exception e){
e.printStackTrace();
}finally{
if(bis!=null){
try {
bis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(bos!=null){
try {
bos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
//获取真实路径
public static String realFileName(String realFileName){
int index = realFileName.lastIndexOf("\\");
if(index>=0){
realFileName = realFileName.substring(index+1);
}
return realFileName;
}
//设置得到uuid的文件路径
public static String makeUuidFilePath(String uploadPath, String uuidFileName) {
String uuidFilePath = null;
int code = uuidFileName.hashCode();//打印文件名的hashcode码，
int dir1 = code & 0xF;//设置一级目录
int dir2 = code>>4 & 0xF;
File file = new File(uploadPath+"/"+dir1+"/"+dir2);
if(!file.exists()){
//如果目录不存在，一次性创建
file.mkdirs();
}
uuidFilePath = file.getPath();
return uuidFilePath;
}
//设置得到uuId的文件名称
public static String makeUuidFileName(String realFileName) {
return UUID.randomUUID().toString()+"_"+realFileName;
}
}

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package zhiwei.deng.web.servlet.upload;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.List;
import java.util.UUID;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import zhiwei.deng.web.servlet.domain.User;
import zhiwei.deng.web.servlet.exception.NoFileUpException;
import zhiwei.deng.web.servlet.exception.UpFileSizeException;
import zhiwei.deng.web.servlet.exception.UpFileTypeException;
import zhiwei.deng.web.servlet.util.UploadUtil;
public class UploadServlet extends HttpServlet {
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
try {
User user = UploadUtil.doUpload(request);
//得到上传的临时路径
String uploadPath = this.getServletContext().getRealPath(UploadUtil.uploadPath);
UploadUtil.doSave(user, uploadPath);
request.setAttribute("message", "上传成功");
request.getRequestDispatcher("/WEB-INF/message.jsp").forward(request, response);
}catch(UpFileSizeException e){
request.setAttribute("message", "上传的文件的大小超过200K");
request.getRequestDispatcher("/WEB-INF/message.jsp").forward(request, response);
}catch(UpFileTypeException e){
request.setAttribute("message","上传文件格式不对，只能为JPG格式的");
request.getRequestDispatcher("/WEB-INF/message.jsp").forward(request, response);
}catch(NoFileUpException e){
request.setAttribute("message", "没有上传文件");
request.getRequestDispatcher("/WEB-INF/message.jsp").forward(request, response);
}catch (Exception e) {
e.printStackTrace();
request.setAttribute("message","上传失败");
request.getRequestDispatcher("/WEB-INF/message.jsp").forward(request, response);
}
}
}

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jsp的代码
<%@ page language="java" pageEncoding="utf-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<script type="text/javascript">
var count = 0;
function addFile(addButton){
var divElement = document.createElement("div");
var inputElement1 = document.createElement("input");
inputElement1.type="file";
inputElement1.name="upfile";
var inputElement2 = document.createElement("input");
inputElement2.type="button";
inputElement2.value="删除";
//针对删除按钮添加一个事件监听
inputElement2.onclick=function(){
var OutIdDivElement = this.parentNode.parentNode;
OutIdDivElement.removeChild(this.parentNode);
count--;
if(count<5){
addButton.disabled=false;
}
}
//依次将他们联系起来
divElement.appendChild(inputElement1);
divElement.appendChild(inputElement2);
var outIdDivElement = document.getElementById("outId");
outIdDivElement.appendChild(divElement);
//判断5次生效的情况
count++;
if(count==5){
addButton.disabled=true;
}
}
</script>
<body>
<form action="${pageContext.request. contextPath}/UploadServlet" method="post" enctype="multipart/form-data">
<table border="1px" align="center">
<caption>上传文件</caption>
<tr>
<th>用户名:</th>
<td><input type="text" name="username"/></td>
</tr>
<tr>
<th>文件名:</th>
<td><input type="file" name="upfile"/>
<input type="button" value="删除"/>
</td>
</tr>
<td colspan="2" align="center">
<div id="outId">
<%--<div>
<input type="file" name="upfile"/>
<input type="button" name="删除"/>
</div> --%>
</div>
</td>
<tr>
<td colspan="2" align="center">
<input type="button" value="添加上传文件" onclick="addFile(this)"/>
</td>
</tr>
<tr>
<td align="center"><input type="submit" value="上传"/></td>
<td align="center"><a href="${pageContext.request.contextPath}/ListFileServlet">下载列表</a></td>
</tr>
</table>
</form>
</body>
</html>

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