JSP用common-fileupload实现文件上传下载

我就是我 2023-10-16 22:49 2阅读 0赞

一、 commons-fileupload是个组件,为jsp应用添加文件上传功能。

common-fileupload组件是apache的一个开源项目之一，可以从[http://jakarta.apache.org/commons/fileupload/][http_jakarta.apache.org_commons_fileupload]下载。

**1）上传页面 upload.jsp**

<form method="post" action="doUp2.jsp" name="frm" enctype="multipart/form-data">
    		<table border="0" width="342" height="136" align="center">
    			<tbody>
    				<tr>
    					<td> 说明:</td>
    					<td> <input type="text" name="ucontent">
    					</td>
    				</tr>
    				<tr>
    					<td> 照片1：</td>
    					<td> <input type="file" name="pic1">
    					</td>
    				</tr>
    				<tr>
    					<td> 照片2：</td>
    					<td> <input type="file" name="pic2">
    					</td>
    				</tr>
    				<tr>
    					<td> 照片3：</td>
    					<td> <input type="file" name="pic3">
    					</td>
    				</tr>
    				<tr>
    					<td> </td>
    					<td><input type="submit" value="上传" name="button1"> <br>
    					</td>
    				</tr>
    			</tbody>
    		</table>
    		<br>
    	</form>

**2)处理页面 doUp2.jsp**

<%
    		//1.指定服务器的路径
    		//D:\apache-tomcat-8.0.12\webapps\jsp3_downup_20151230
    		String paths = request.getSession().getServletContext()
    				.getRealPath("/upload");
    		System.out.println(paths);
    
    		//2.创建文件夹
    		File file = new File(paths);
    		//3.判断不存在，创建文件夹
    		if (!file.exists()) {
    			file.mkdir();
    		}
    
    		/** 3.
    		 * 首先判断form的enctype是不是multipart/form-data 
    		 * 同时也判断了form的提交方式是不是post 
    		 * 方法：isMultipartContent(request) 
    		 */
    		if (ServletFileUpload.isMultipartContent(request)) {
    
    			//4. 实例化一个硬盘文件工厂,用来配置上传组件ServletFileUpload   
    			DiskFileItemFactory factory = new DiskFileItemFactory();
    
    			//5.创建ServletFileUpload对象  
    			ServletFileUpload upload = new ServletFileUpload(factory);
    
    			
    			//设置单个文件最大值byte   100kb
    			upload.setFileSizeMax(100 * 1024);
    
    			//所有上传文件的总和最大值byte  160kb
    			upload.setSizeMax(160 * 1024);
    
    			//
    
    			//6.获得文件上传列表
    			List<FileItem> list = null;
    			
    			
    			//保存上传的文件名
    			List<String> fileNames=new ArrayList<String>();
    
    			try {
    
    				//文件列表允许上传的文件格式
    				List<String> types = Arrays.asList("jpg", "gif", "txt");
    
    				list = upload.parseRequest(request);
    
    				//遍历数据
    				for (FileItem item : list) {
    					//1.是否是普通字段
    					if (item.isFormField()) {
    						System.out.println(item.getFieldName() + "="
    								+ item.getString("utf-8"));
    					} else {
    						//上传文件名
    						String upFile = item.getName();
    
    						//Kaola.jpg/
    						//取扩展名.jpg,.txt
    						String ext = upFile.substring(upFile
    								.lastIndexOf(".") + 1);
    
    						//判断
    						if (!types.contains(ext)) {
    							out.println("上传的文件《"+upFile+"》格式不正确！文件格式必须是"
    									+ types.toString()+"<p/>");
    						} else {
    
                                   //保存文件到集合中
                                   fileNames.add(upFile);
                          
    							//保存文件
    							// @param   parent  The parent abstract pathname
    							//* @param   child   The child pathname string
    							File saveFile = new File(file, upFile);
    
    							//写入
    							item.write(saveFile);
    
    							//查看
    							out.println(upFile + "的大小是：" + item.getSize()
    									+ "字节数！<p/>");
    
    						}
    					
    
    					}
    
    				}
    				
    				//跳转
    			   request.setAttribute("fileNames",fileNames);  
                              request.getRequestDispatcher("download.jsp").forward(request, response);  
    
    			} catch (FileUploadBase.SizeLimitExceededException ee0) {
    				out.println("所有文件大小最大是:" + upload.getSizeMax() + "字节！");
    			} catch (FileSizeLimitExceededException ee1) {
    				out.println("单个文件大小最大是:" + upload.getFileSizeMax() + "字节！");
    			} catch (FileUploadException ex) {
    				ex.printStackTrace();
    			}
    
    		} else {
    			out.println("上传的格式属性不正确！");
    
    		}
    	%>

**3)下载页面down.jsp**

<br>  
         --------------直接下载------------  
         <br>  
          <%  
            List<String> fileNames = (List<String> )request.getAttribute("fileNames");   
            for(String fileName : fileNames) {  
          %>  
           
            <form action="doDown.jsp" method="get">  
                <input type="hidden" name="fileName" value="<%=fileName %>" />  
                <input type="submit" value="下载:<%=fileName %>" />  
            </form>  
         <%  
            }  
         %>  
         <br>  
          --------------直接打开---------  
         <%   
           for(String fileName : fileNames) {  
          %>  
            <form action="doDown.jsp" method="get">  
                <input type="hidden" name="fileName" value="<%=fileName %>" />  
                <input type="hidden" name="online" value="yes" />  
                <input type="submit" value="打开:<%=fileName %>" />  
            </form>  
         <%  
            }  
         %>  
         </br>

**4)处理下载页面 doDown.jsp**

<%
    		//指定服务器路径
    		String fileDir = request.getSession().getServletContext()
    				.getRealPath("/upload");
    
    		//中文处理
    		request.setCharacterEncoding("utf-8");
    
    		//表单请求的值
    		String aFileName = request.getParameter("fileName");
    		String online = request.getParameter("online");
    
    		//输入流
    		FileInputStream in = null;
    		//输出流
    		ServletOutputStream outs = null;
    
    		//判断是否占线
    		boolean isOnLine = online != null ? true : false;
    		try {
    
    			if (isOnLine) {
    				URL u = new URL("file:///" + fileDir + aFileName);
    				//设置头信息
    				response.setContentType(u.openConnection().getContentType());
    				response.setHeader("Content-Disposition",
    						"inline; filename=" + aFileName);
    			} else {
    				///设置内容类型和头信息
    				response.setContentType("application/x-msdownload");
    				response.setHeader("Content-Disposition",
    						"attachment; filename=" + aFileName);
    			}
    
    			in = new FileInputStream(fileDir + "\\" + aFileName);
    			outs = response.getOutputStream();
    			outs.flush();
    
    			//读取
    			int aRead = 0;
    			while ((aRead = in.read()) != -1 & in != null) {
    				outs.write(aRead); //写入
    			}
    			outs.flush(); //刷新
    			
    		//发生异常：java.lang.IllegalStateException: getOutputStream() has already been called for this response
    			   out.clear();
    			   out = pageContext.pushBody();
    			
    			///
    			
    			
    
    		} catch (Throwable e) {
    			e.printStackTrace();
    		} finally {
    			try { //关闭
    				in.close();
    				outs.close();
    			} catch (Throwable e) {
    				e.printStackTrace();
    			}
    		}
    		
    		
    	%>

总结：通过 common-fileupload 组件实现了上传和下载功能。

上传功能：可以上传一个或多个文件，可以控制单个上传文件的大小，也可以控制所有文件上传的总大小，还可以限制上传 文件的格式。

下载功能：可以直接下载，也可以直接打开内容。

[http_jakarta.apache.org_commons_fileupload]: http://jakarta.apache.org/commons/fileupload/