JavaWeb09_文件上传下载

小咪咪 2022-10-27 15:58 233阅读 0赞

**文件上传下载**

**文件上传：**

在文件上传的 jsp 页面中的 form 表单提交方法需设置为post，enctype属性需设置为 multipart/form-data

测试上传文件：aaaa.txt

静夜思
    李白
    床前明月光，
    疑是地上霜。
    举头望明月，
    低头思故乡。

文件上传处理Servlet类

@WebServlet("/upload")
    public class upload extends HttpServlet { 
    	
    	@Override
    	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
    		InputStream inputStream = req.getInputStream();
    		InputStreamReader reader = new InputStreamReader(inputStream);
    		BufferedReader bufferedReader = new BufferedReader(reader);
    		String str = "";
    		while((str = bufferedReader.readLine())!=null) { 
    			System.out.println(str);
    		}
    		
    	}
    
    }

结果：

------WebKitFormBoundaryLYiNnAkdP2Nnf1hS
    Content-Disposition: form-data; name="image"; filename="aaaa.txt"
    Content-Type: text/plain
    
    静夜思
    李白
    床前明月光，
    疑是地上霜。
    举头望明月，
    低头思故乡。
    ------WebKitFormBoundaryLYiNnAkdP2Nnf1hS--

--------------------

**使用 fileupload 组件实现文件上传**

需要的 jar 包：**commons-fileupload-1.3.1.jar** 和 **commons-io-2.5.jar**

@WebServlet("/upload")
    public class upload extends HttpServlet { 
    	
    	@Override
    	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
    		
    		try { 
    			DiskFileItemFactory fileItemFactory = new DiskFileItemFactory();
    			ServletFileUpload servletFileUpload = new ServletFileUpload(fileItemFactory);
    			List<FileItem> list = servletFileUpload.parseRequest(req);
    			for(FileItem fileItem : list) { 
    				//文件名（如果上传的不是文件则为null）
    				System.out.println(fileItem.getName());
    				//表单input中的name参数
    				System.out.println(fileItem.getFieldName());
    				if(fileItem.isFormField()) { 
    					//如果不是文件
    					String name = fileItem.getFieldName();
    					String value = fileItem.getString("UTF-8");
    					System.out.println(name+":"+value);
    				}else { 
    					//如果是文件
    					String fileName = fileItem.getName();
    					long size = fileItem.getSize();
    					System.out.println(fileName+":"+size+"Byte");
    					InputStream inputStream = fileItem.getInputStream();
    					String path = req.getServletContext().getRealPath("uploadFolder/"+fileName);
    					OutputStream outputStream = new FileOutputStream(path);
    					int temp = 0;
    					while((temp = inputStream.read())!=-1) { 
    						outputStream.write(temp);
    					}
    					outputStream.close();
    					inputStream.close();
    					System.out.println("上传成功！");
    				}
    			}
    		} catch (FileUploadException e) { 
    			e.printStackTrace();
    		}
    	}
    
    }

--------------------

**文件下载：**

@WebServlet("/download")
    public class DownloadServlet extends HttpServlet { 
    	
    	@Override
    	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
    		//设置响应方式
    		resp.setContentType("application/x-msdownload");
    		//设置文件名
    		String fileName = "buer.jpg";
    		resp.setHeader("Content-Disposition", "attachment;filename="+fileName);
    		//获取输出流
    		OutputStream outputStream = resp.getOutputStream();
    		String path = req.getServletContext().getRealPath("static/image/buer.jpg");
    		System.out.println(path);
    		InputStream inputStream = new FileInputStream(path);
    		int temp = 0;
    		while((temp=inputStream.read())!=-1) { 
    			outputStream.write(temp);
    		}
    		inputStream.close();
    		outputStream.close();
    	}
    
    }