文件的上传和下载(upload)

private List<String> fileTypes=new ArrayList<String>();//定义一个集合,里面是文件类型的字符串

public void init() throws ServletException {
		String contenttype=this.getInitParameter("contenttype");
		String[] contenttypes=contenttype.split(";");
		for(String ct:contenttypes){
			fileTypes.add(ct);
		}
	}

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		try {
			response.setContentType("text/html;charset=utf-8");
			PrintWriter out=response.getWriter();
			// Check that we have a file upload request
			// 检查我们有一个文件上传请求
			boolean isMultipart = ServletFileUpload.isMultipartContent(request);
			if(isMultipart){
				//说明request中有一个文件
				// Create a factory for disk-based file items
				//创建一个磁盘文件条目工厂,工厂生产对象
				DiskFileItemFactory factory = new DiskFileItemFactory();
				// Create a new file upload handler
				ServletFileUpload upload = new ServletFileUpload(factory);
				// Parse the request
				//把request中的数据,转换成list集合,元素类型为fileItem
				List<FileItem> items = upload.parseRequest(request);
				// Process the uploaded items
				//处理上传的条目
				Iterator<FileItem> iter = items.iterator();
				while (iter.hasNext()) {
				    FileItem item = iter.next();
				    if (item.isFormField()) {
				    	//是非文件域,除了文件之外的input
				        String name=item.getFieldName();//<input name>
				        String value=item.getString();//<input value>
				        System.out.println(name+" "+value);
				        if("note".equals(name)){
				        	String noteValue=item.getString();
				        }
				    } else {
				    	//是文件域<input type="file"processUploadFile(item)
				    	String fieldName=item.getFieldName();
				    	String fileName=item.getName();//获取真实文件名
				    	String contentType=item.getContentType();//获取文件内容类型
				    	boolean isInMemory=item.isInMemory();//是否在内存中
				    	long sizeInBytes=item.getSize();//获取文件的长度
				    	System.out.println(fieldName+" "+fileName+" "+contentType+" "+isInMemory+" "+sizeInBytes);
				    	//处理获取真实的文件名,因为浏览器的差异,导致文件名前带有路径,用此功能去掉路径
				    	if(fileName!=null){
				    		fileName=FilenameUtils.getName(fileName);
				    	}
				    	if(fileTypes.contains(contentType)){
				    		if(sizeInBytes<4194304){
				    		//准备上传文件在服务器的存储路径
					    	String realPath=this.getServletContext().getRealPath("/upload");
					    	System.out.println(realPath);
					    	File file=new File(realPath);
					    	if(!file.exists()){
					    		file.mkdir();
					    	}
					    	//把文件上传到upload文件夹
					    	File uploadFile=new File(file,fileName);
					    	item.write(uploadFile);//把文件写到具体路径
					    	out.println("<div sty='color:red;'>上传文件成功</div>");
				    		}else{
				    			out.println("<div sty='color:red;'>文件太大</div>");
				    		}
				    	}else{
				    		out.println("<div sty='color:red;'>文件类型不匹配</div>");
				    	}
				    	
				    }
				    
				}
			}
			out.flush();
			out.close();
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//获取要下载的文件名
		String fileName=request.getParameter("fileName");
		//检测文件在服务器中是否存在
		String realPath=this.getServletContext().getRealPath("/upload");
		//拼装一个完整的路径
		String allPath=realPath+File.separator+fileName;
		System.out.println("allPath="+allPath);
		File file=new File(allPath);
		if(file.exists()){
			//文件存在可以下载
			//要想下载文件,必须给response对象设置一个消息头
			response.setHeader("Content-Disposition", "attachment;filename="+new String(fileName.getBytes("utf-8"),"ISO8859-1"));
			//开始下载文件
			OutputStream os=response.getOutputStream();
			//先从服务器本地把文件读入到内存中
			InputStream is=new FileInputStream(file);
			byte[] buf=new byte[1024];
			int len=-1;
			while((len=is.read(buf))!=-1){
				os.write(buf,0,len);
			}
			os.flush();
			os.close();
			is.close();
		}
	}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.setContentType("text/x-msdownload");
		response.setHeader("Content-Disposition", "attachment;filename=download.csv");
		OutputStream os=response.getOutputStream();
		String csvText="";
		for(int i=0;i<10;i++){
			for(int j=0;j<10;j++){
				csvText+=i*j+",";
			}
			csvText+="\n";
		}
		os.write(csvText.getBytes(),0,csvText.length());
		os.flush();
		os.close();
	}