java 文件上传 下载 总结

首先引入2个jar
![](http://images2017.cnblogs.com/blog/1128666/201711/1128666-20171101145630498-2084371020.png)

package uploaddownload;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.sql.Savepoint;
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.FileUploadBase;
import org.apache.commons.fileupload.ProgressListener;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
/**
 *
 * @ClassName UploadBoost
 * @Description TODO(这里用一句话描述这个类的作用)
 * @Author pengzh humi
 * @Date 2017年11月1日 上午10:38:36
 */
public class UploadBoost extends HttpServlet{

	private static final long serialVersionUID = 1L;

	@Override
	public void init() throws ServletException {
		System.out.println("UploadBoost init ...");
	}
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		System.out.println("DO Get method ...");
		String saveFile = this.getServletContext().getRealPath("/WEB-INF/upload");
		String tempPath = this.getServletContext().getRealPath("/WEB-INF/temp");
		File tempFile = new File(tempPath);
		if(!tempFile.exists()){
			tempFile.mkdir();
		}
		//消息提示
		String message="";
		InputStream in =null;
		FileOutputStream out = null;

		try {
			DiskFileItemFactory factory = new DiskFileItemFactory();
			factory.setSizeThreshold(1024*1024*5);//5k缓存
			factory.setRepository(tempFile);//临时保存路径
			ServletFileUpload upload = new ServletFileUpload(factory);//创建文件解析器
			upload.setProgressListener(new ProgressListener() {//上传进度
				public void update(long finished, long total, int rate) {
					// TODO Auto-generated method stub
					System.out.println("文件上传进度"+finished+"/"+total+"|"+Math.floor((double)(finished*100/total))+"% rate="+rate);
				}
			});
			upload.setHeaderEncoding("utf-8");//解决文件名乱码
			if(!ServletFileUpload.isMultipartContent(req)){
				message = "非媒体文件上传";
				return;
			}
			upload.setFileSizeMax(1024*1024*5);//设置单个文件上传最大为5M
			upload.setSizeMax(1024*1024*10);//设置上传文件总量最大值为5M

			List<FileItem> fileList = upload.parseRequest(req);
			for (FileItem item : fileList) {
				if(item.isFormField()){
					System.out.println("表单数据：name="+item.getFieldName()+" value="+item.getString("utf-8"));
				}else{
					String fileName =item.getName();
					if(fileName==null||fileName.trim().equals("")){
						continue;
					}
					System.out.println("上传的文件名："+fileName);
					fileName = getFileName(fileName.substring(fileName.lastIndexOf("\\")+1));//得到唯一文件名
					String fileExtName=fileName.substring(fileName.lastIndexOf(".")+1);//得到后缀名
					String dir = getPaht(fileName, saveFile);
					System.out.println("唯一文件名："+fileName+"\n文件扩展名"+fileExtName+"\n保存路径名："+saveFile+"\n哈希路径："+dir);
					in = item.getInputStream();
					out = new FileOutputStream(dir+"\\"+fileName);
					byte[] buff= new byte[1024];//字节流 1k缓冲
					int length=0;//文件标记位
					while((length=in.read(buff, 0, length))>0){
						out.write(buff, 0, length);
					}
				message="文件上传成功";
				}
			}
		}catch (FileUploadBase.FileSizeLimitExceededException  e) {
			System.out.println("上传失败   "+e.getMessage());
			message="上传失败   "+e.getMessage();
		}catch (FileUploadBase.SizeLimitExceededException e) {
			System.out.println("上传失败   "+e.getMessage());
			message="上传失败   "+e.getMessage();
		}catch (Exception e) {
			System.out.println("上传失败   "+e.getMessage());
			message="上传失败   "+e.getMessage();
		}finally{
			//关闭流 并置空 让JVM去回收
			out.close();out=null;
			in.close();in=null;
			//消息提示
			System.out.println("message="+message);
			req.setAttribute("message", message);
			req.getRequestDispatcher("/message.jsp").forward(req, resp);
		}

	}

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		System.out.println("Do Post method ...");
		doGet(req, resp);
	}
	/**
	 *
	 * @param name
	 * @return 唯一文件名
	 */
	public String getFileName(String name){
		return UUID.randomUUID().toString()+"_"+name;
	}
	/**
	 *
	 * @param name
	 * @param path
	 * @return 得到哈希路径
	 */
	public String getPaht(String name,String path){
		int hashcode = name.hashCode();
		int dir1 = hashcode&0xf;
		int dir2 = dir1>>4;
//		System.out.println("hashcode="+hashcode+"\ndir1="+dir1+"\ndir2="+dir2);
		String dir = path +"\\"+dir1+"\\"+dir2;
		File file = new File(dir);
		if(!file.exists()){
			file.mkdirs();
//			System.out.println("file==="+file+"   "+file.toURI());
		}
		return dir;
	}
}

===============================================================

package uploaddownload;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URLEncoder;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 *
 * @ClassName DownLoadServlet
 * @Description 文件下载
 * @Author pengzh humi
 * @Date 2017年11月2日 下午8:10:20
 */
public class DownLoadServlet extends HttpServlet{

	private static final long serialVersionUID = 1L;

	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		String realPaht= this.getServletContext().getRealPath("/WEB-INF/upload");
		String fileName =req.getParameter("filename");
		String filePath =findFileBySavePath(fileName, realPaht);
		File file = new File(filePath+"\\"+fileName);//得到需要下载的文件
		System.out.println("文件下载 DownLoadServlet 路径"+filePath+"\\"+fileName);
		if(!file.exists()){
			req.setAttribute("message", "你要下载的文件已删除");
			req.getRequestDispatcher("/message.jsp").forward(req, resp);
			return;
		}
		fileName = fileName.substring(fileName.lastIndexOf('_')+1);
		 //设置响应头，控制浏览器下载该文件
		resp.setHeader("content-disposition", "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8"));
		OutputStream out=resp.getOutputStream();
		FileInputStream in = new FileInputStream(file);
		int len =0;
		byte[] buff= new byte[1024];
		System.out.println("将下载  DownLoadServlet: "+fileName);
		while((len=in.read(buff))>0){
			out.write(buff, 0, len);
		}
	}

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		doGet(req, resp);
	}
	/**
	 *
	 * @param fileName 	文件名
	 * @param savePath	下载后保存的路径
	 * @return
	 */
	public String findFileBySavePath(String fileName,String savePath){
		int hashCode = fileName.hashCode();
		int dir1 = hashCode&0xf;
		int dir2 = dir1>>4;
		String dir = savePath+"\\"+dir1+"\\"+dir2;
		System.out.println("保存目录处理：dir1="+dir1+"  dir2="+dir2+" dir="+dir);
		File file = new File(dir);
		if(!file.exists()){
			file.mkdirs();
		}
		return dir;
	}
}