今天了解了一下javaweb的上传与下载的简单功能的实现。通过这个小demo可以实现将本地的文件下载至sever服务器的指定文件夹中。以及将项目文件夹里的指定文件下载至本计算机中。具体界面如下图所示，点击提交可以上传图片，点击图片这个超链接可实现图片的下载
具体代码如下：
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>Insert title here</title> </head> <body> <!-如果上传文件表单的提交方式必须为post,且form中必须有enctype="multipart/form-data" -> <form action="UploadServlet" method="post" enctype="multipart/form-data"> 学号:<input type="text" name="sno"/><br/> 姓名:<input type="text" name="sno"/><br/> 上传照片:<input type="file" name="spicture"/><br/> <input type="submit" value="提交"/> </form> <a href="DownloadServlet?filename=图片.png">图片</a> </body> </html>
package studentServlet; import java.io.IOException; import java.io.InputStream; import java.net.URLEncoder; import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Servlet implementation class DownloadServlet */ @WebServlet("/DownloadServlet") public class DownloadServlet extends HttpServlet { private static final long serialVersionUID = 1L; /** * @see HttpServlet#HttpServlet() */ public DownloadServlet() { super(); // TODO Auto-generated constructor stub } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //获取需要下载的文件名 String fileName = request.getParameter("filename");//form ,a href ,servlet?a=b //下载文件徐设置消息头 response.addHeader("content-Type", "aspplication/octet/stream");//MIME类型：二进制类型的(所有的内容都可以下载) response.addHeader("content-Disposition", "attachment;filename="+URLEncoder.encode(fileName,"UTF-8")); //Servlet通过文件的地址将文件转为输入流读到Servlet中 InputStream in = getServletContext().getResourceAsStream("/res/图片.png"); //通过输出流，将刚刚已转为输入流的文件输出给用户 ServletOutputStream out = response.getOutputStream(); byte[] bs = new byte[10]; int len=-1; while((len=in.read(bs))!=-1) { out.write(bs,0,len); } out.close(); in.close(); } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub doGet(request, response); } }
package studentServlet; import java.io.File; import java.io.IOException; import java.util.Iterator; import java.util.List; 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 org.apache.commons.fileupload.FileItem; import org.apache.commons.fileupload.FileItemFactory; import org.apache.commons.fileupload.FileUploadBase; import org.apache.commons.fileupload.FileUploadException; import org.apache.commons.fileupload.disk.DiskFileItemFactory; import org.apache.commons.fileupload.servlet.ServletFileUpload; /** * Servlet implementation class UploadServlet */ @WebServlet("/UploadServlet") public class UploadServlet extends HttpServlet { private static final long serialVersionUID = 1L; /** * @see HttpServlet#HttpServlet() */ public UploadServlet() { super(); // TODO Auto-generated constructor stub } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("utf-8");//设置请求编码 response.setCharacterEncoding("utf-8");//设置响应编码 response.setContentType("text/html; charset=UTF-8");//设置响应界面编码 boolean isMultiPart = ServletFileUpload.isMultipartContent(request); try { if(isMultiPart) {//判断前台form是否有enctype="multipart/form-data"字段 DiskFileItemFactory factory = new DiskFileItemFactory(); ServletFileUpload upload = new ServletFileUpload(factory); String temppath = request.getSession().getServletContext().getRealPath("loadtemp"); factory.setSizeThreshold(20480);//设置临时缓冲区文件大小 factory.setRepository(new File(temppath)); //控制单个文件的大小 upload.setSizeMax(40960);//字节B //通过ParseRequest解析form中的所有请求字段，并保存到items集合当中 List<FileItem> items = upload.parseRequest(request); //遍历items中的数据 Iterator<FileItem> iter = items.iterator(); while(iter.hasNext()) { FileItem item = iter.next(); String itemName = item.getFieldName(); int sno = -1; String sname = null; if(item.isFormField()) {//判断前台字段是普通form表单字段还是文件字段 if(itemName.equals("sno")) { sno = Integer.parseInt(item.getString("UTF-8")); }else if(itemName.equals("sname")) { sname = item.getString("UTF-8"); }else { System.out.println("其他字段。。。"); } }else { //文件上传 //文件名getFieldName是获取普通表单字段的name的值 //getName()是获取文件名 String fileName = item.getName(); String ext = fileName.substring(fileName.indexOf(".")+1); if(!(ext.equals("png")||ext.equals("jpg")||ext.equals("gif"))) { System.out.println("照片格式有误，只能是png,jpg,gif格式"); return; } //获取文件内容并上传 //定义文件路径：指定上传位置 //获取服务器路径: String path = request.getSession().getServletContext().getRealPath("load"); File file = new File(path,fileName); item.write(file); System.out.println("上传成功!!!"); return; } } } }catch (FileUploadBase.SizeLimitExceededException e) { System.out.println("文件超出最大传输范围，不能超过40kb"); } catch (FileUploadException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub doGet(request, response); } }
其中index.jsp是页面的代码，DownloadServlet是下载的servlet代码，UploadServlet是上传的代码。
今天的学习就到这里，明天打算学习一下javaweb的EL以及jstl。