Jsp+Servlet实现文件上传下载 文件上传（一）（jsp+servlet follow）怎么可以错过

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadBase;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.ProgressListener;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Calendar;
import java.util.Iterator;
import java.util.List;
import java.util.UUID;

@WebServlet(“/UploadServlet”)
public class UploadServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//设置文件上传基本路径
String savePath=this.getServletContext().getRealPath(“/WEB-INF/uploadFiles”);
//设置临时文件路径
String tempPath=this.getServletContext().getRealPath(“/WEB-INF/tempFiles”);
File tempFile=new File(tempPath);
if (!tempFile.exists()) {
tempFile.mkdir();
}

//定义异常消息
String errorMessage=””;
//创建file items工厂
DiskFileItemFactory factory=new DiskFileItemFactory();
//设置缓冲区大小
factory.setSizeThreshold(1024 * 100);
//设置临时文件路径
factory.setRepository(tempFile);
//创建文件上传处理器
ServletFileUpload upload=new ServletFileUpload(factory);
//监听文件上传进度
ProgressListener progressListener=new ProgressListener() {
public void update(long pBytesRead, long pContentLength, int pItems) {
System.out.println(“正在读取文件： ” + pItems);
if (pContentLength==-1) {
System.out.println(“已读取： ” + pBytesRead + ” 剩余0″);
} else {
System.out.println(“文件总大小：” + pContentLength + ” 已读取：” + pBytesRead);
}
}
};
upload.setProgressListener(progressListener);

//解决上传文件名的中文乱码
upload.setHeaderEncoding(“UTF-8″);
//判断提交上来的数据是否是上传表单的数据
if (!ServletFileUpload.isMultipartContent(request)) {
//按照传统方式获取数据
return;
}

//设置上传单个文件的大小的最大值，目前是设置为1024*1024字节，也就是1MB
upload.setFileSizeMax(1024 * 1024);
//设置上传文件总量的最大值，最大值=同时上传的多个文件的大小的最大值的和，目前设置为10MB
upload.setSizeMax(1024 * 1024 * 10);

try {
//使用ServletFileUpload解析器解析上传数据，解析结果返回的是一个List<FileItem>集合，每一个FileItem对应一个Form表单的输入项
List<FileItem> items=upload.parseRequest(request);
Iterator<FileItem> iterator=items.iterator();
while (iterator.hasNext()) {
FileItem item=iterator.next();

//判断jsp提交过来的是不是文件
if (item.isFormField()) {
errorMessage=”请提交文件！”;
break;
} else {
//文件名
String fileName=item.getName();
if (fileName==null || fileName.trim()==””) {
System.out.println(“文件名为空！”);
}
//处理不同浏览器提交的文件名带路径问题
fileName=fileName.substring(fileName.lastIndexOf(“\”) + 1);
//文件扩展名
String fileExtension=fileName.substring(fileName.lastIndexOf(“.”) + 1);
//判断扩展名是否合法
if (!validExtension(fileExtension)) {
errorMessage=”上传文件非法！”;
item.delete();
break;
}
//获得文件输入流
InputStream in=item.getInputStream();
//得到保存文件的名称
String saveFileName=createFileName(fileName);
//得到文件保存路径
String realFilePath=createRealFilePath(savePath, saveFileName);
//创建文件输出流
FileOutputStream out=new FileOutputStream(realFilePath);
//创建缓冲区
byte buffer[]=new byte[1024];
int len=0;
while ((len=in.read(buffer)) > 0) {
//写文件
out.write(buffer, 0, len);
}
//关闭输入流
in.close();
//关闭输出流
out.close();
//删除临时文件 TODO
item.delete();
//将上传文件信息保存到附件表中 TODO
}

}

} catch (FileUploadBase.FileSizeLimitExceededException e) {
e.printStackTrace();
request.setAttribute(“errorMessage”, “单个文件超出最大值！！！”);
request.getRequestDispatcher(“pages/upload/upload.jsp”).forward(request, response);
return;
} catch (FileUploadBase.SizeLimitExceededException e) {
e.printStackTrace();
request.setAttribute(“errorMessage”, “上传文件的总的大小超出限制的最大值！！！”);
request.getRequestDispatcher(“pages/upload/upload.jsp”).forward(request, response);
return;
} catch (FileUploadException e) {
e.printStackTrace();
request.setAttribute(“errorMessage”, “文件上传失败！！！”);
request.getRequestDispatcher(“pages/upload/upload.jsp”).forward(request, response);
return;
}

request.setAttribute(“errorMessage”, errorMessage);
request.getRequestDispatcher(“pages/upload/upload.jsp”).forward(request, response);

}

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}

private boolean validExtension(String fileExtension) {
String[] exts=