java ee页面上如何上传下载和展示文件？
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这篇文章主要讲解了“java ee页面上如何上传下载和展示文件?”，文中的讲解内容简单清晰，易于学习与理解，下面请大家跟着小编的思路慢慢深入，一起来研究和学习“java ee页面上如何上传下载和展示文件?”吧! 接着上一篇讲： Jsp+Servlet实现文件上传下载(一)--文件上传 本章来实现一下上传文件列表展示，同时优化了一下第一章中的代码。 废话少说，上代码 mysql创建附件表 DROP TABLE tbl_accessory; CREATE TABLE tbl_accessory ( id INT AUTO_INCREMENT PRIMARY KEY, file_name VARCHAR(500), file_size DOUBLE(10,2), file_ext_name VARCHAR(100), file_path VARCHAR(2000) ) ; SELECT * FROM tbl_accessory; DELETE FROM tbl_accessory; 创建附件实体类 package entity.upload; /** * 附件实体类 * * @author xusucheng * @create 2017-12-29 **/ public class EntityAccessory { private int id; private String fileName; private double fileSize; private String file_ext_name; private String filePath; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getFileName() { return fileName; } public void setFileName(String fileName) { this.fileName = fileName; } public double getFileSize() { return fileSize; } public void setFileSize(double fileSize) { this.fileSize = fileSize; } public String getFile_ext_name() { return file_ext_name; } public void setFile_ext_name(String file_ext_name) { this.file_ext_name = file_ext_name; } public String getFilePath() { return filePath; } public void setFilePath(String filePath) { this.filePath = filePath; } } 创建DBUtil工具类 package util; import java.sql.*; import java.io.InputStream; import java.util.Properties; /** * 数据库工具类 * * @author xusucheng * @create 2017-11-18 **/ public class DBUtil { //定义链接所需要的变量 private static Connection con = null; private static PreparedStatement ps = null; private static ResultSet rs = null; //定义链接数据库所需要的参数 private static String url = ""; private static String username = ""; private static String driver=""; private static String password=""; //定义读取配置文件所需要的变量 private static Properties pp = null; private static InputStream fis = null; /** * 加载驱动 */ static { try { //从dbinfo.properties配置文件中读取配置信息 pp = new Properties(); fis = DBUtil.class.getClassLoader().getResourceAsStream("db.properties"); pp.load(fis); url = pp.getProperty("url"); username = pp.getProperty("username"); driver=pp.getProperty("driver"); password=pp.getProperty("password"); //加载驱动 Class.forName(driver); } catch (Exception e) { System.out.println("驱动加载失败!"); e.printStackTrace(); } finally { try { fis.close(); } catch (Exception e) { e.printStackTrace(); } fis = null; //垃圾回收自动处理 } } /** * 得到Connection链接 * @return Connection */ public static Connection getConnection() { try { //建立连接 con = DriverManager.getConnection(url, username, password); } catch (Exception e) { System.out.println("数据库链接失败!"); e.printStackTrace(); } return con; } /*public DBUtil(String sql){ try { ps = getConnection().prepareStatement(sql);//准备执行语句 } catch (Exception e) { e.printStackTrace(); } } public void close() { try { con.close(); ps.close(); } catch (SQLException e) { e.printStackTrace(); } }*/ /** * 统一的资源关闭函数 * @param rs * @param ps * @param con */ public static void close(ResultSet rs,Statement ps, Connection con){ if(rs != null) { try { rs.close(); } catch (Exception e) { e.printStackTrace(); } } if(ps != null) { try { ps.close(); } catch (Exception e) { e.printStackTrace(); } } if(con != null) { try { con.close(); } catch (Exception e) { e.printStackTrace(); } } } } 创建附件实体DAO类 package dao.upload; import entity.upload.EntityAccessory; import util.DBUtil; import java.math.BigDecimal; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.ArrayList; import java.util.List; /** * 附件上传DAO * * @author xusucheng * @create 2017-12-29 **/ public class AccessoryDao { public static void add(EntityAccessory entity) { Connection conn = DBUtil.getConnection(); String sql = "insert into tbl_accessory(file_name,file_size,file_ext_name,file_path) values(?,?,?,?)"; try { PreparedStatement ps = conn.prepareStatement(sql); ps.setString(1, entity.getFileName()); ps.setDouble(2, entity.getFileSize()); ps.setString(3, entity.getFile_ext_name()); ps.setString(4, entity.getFilePath()); ps.execute(); //conn.commit(); DBUtil.close(null, ps, conn); } catch (SQLException e) { e.printStackTrace(); } } public static List Connection conn = DBUtil.getConnection(); String sql = "select id,file_name,file_size,file_ext_name,file_path from tbl_accessory"; List try { PreparedStatement ps = conn.prepareStatement(sql); ResultSet rs = ps.executeQuery(); while (rs.next()) { EntityAccessory entity = new EntityAccessory(); entity.setId(rs.getInt("id")); entity.setFileName(rs.getString("file_name")); entity.setFileSize(new BigDecimal(rs.getDouble("file_size") / 1024).setScale(2, BigDecimal.ROUND_HALF_UP).doubleValue()); entity.setFile_ext_name(rs.getString("file_ext_name")); entity.setFilePath(rs.getString("file_path")); accessoryList.add(entity); } DBUtil.close(rs, ps, conn); } catch (SQLException e) { e.printStackTrace(); } return accessoryList; } public static void remove(int id) { Connection conn = DBUtil.getConnection(); String sql = "delete from tbl_accessory where id=?"; try { PreparedStatement ps = conn.prepareStatement(sql); ps.setInt(1,id); ps.execute(); //conn.commit(); mysql默认开启了autocommit DBUtil.close(null,ps,conn); } catch (SQLException e) { e.printStackTrace(); } } } 创建list.jsp列表页面
文件列表
创建展示列表Servlet:listUploadedFilesServlet package servlet.upload; import dao.upload.AccessoryDao; import entity.upload.EntityAccessory; 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 java.io.IOException; import java.util.List; /** * 返回已上传文件列表 * * @author xusucheng * @create 2017-12-29 **/ @WebServlet("/listUploadedFiles") public class listUploadedFilesServlet extends HttpServlet { @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //获取文件列表 List request.setAttribute("accessoryList", accessoryList); request.getRequestDispatcher("pages/upload/list.jsp").forward(request, response); } @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request, response); } } 增加error.jsp显示上传失败信息 <%@ page contentType="text/html;charset=UTF-8" language="java" %> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
上传失败：
<%----%>
${errorMessage}
优化了第一章中的上传控制器 package servlet.upload; import dao.upload.AccessoryDao; import entity.upload.EntityAccessory; import org.apache.commons.fileupload.FileItem; import org.apache.commons.fileupload.FileUploadBase; import org.apache.commons.fileupload.FileUploadException; import org.apache.commons.fileupload.ProgressListener; import org.apache.commons.fileupload.disk.DiskFileItemFactory; import org.apache.commons.fileupload.servlet.ServletFileUpload; 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 java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.util.Calendar; import java.util.Iterator; import java.util.List; import java.util.UUID; /** * 处理文件上传 * * @author xusucheng * @create 2017-12-27 **/ @WebServlet("/UploadServlet") public class UploadServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //设置文件上传基本路径 String savePath = this.getServletContext().getRealPath("/WEB-INF/uploadFiles"); //设置临时文件路径 String tempPath = this.getServletContext().getRealPath("/WEB-INF/tempFiles"); File tempFile = new File(tempPath); if (!tempFile.exists()) { tempFile.mkdir(); } //定义异常消息 String errorMessage = ""; //创建file items工厂 DiskFileItemFactory factory = new DiskFileItemFactory(); //设置缓冲区大小 factory.setSizeThreshold(1024 * 100); //设置临时文件路径 factory.setRepository(tempFile); //创建文件上传处理器 ServletFileUpload upload = new ServletFileUpload(factory); //监听文件上传进度 ProgressListener progressListener = new ProgressListener() { public void update(long pBytesRead, long pContentLength, int pItems) { System.out.println("正在读取文件： " + pItems); if (pContentLength == -1) { System.out.println("已读取： " + pBytesRead + " 剩余0"); } else { System.out.println("文件总大小：" + pContentLength + " 已读取：" + pBytesRead); } } }; upload.setProgressListener(progressListener); //解决上传文件名的中文乱码 upload.setHeaderEncoding("UTF-8"); //判断提交上来的数据是否是上传表单的数据 if (!ServletFileUpload.isMultipartContent(request)) { //按照传统方式获取数据 return; } //设置上传单个文件的大小的最大值，目前是设置为1024*1024字节，也就是1MB //upload.setFileSizeMax(1024 * 1024); //设置上传文件总量的最大值，最大值=同时上传的多个文件的大小的最大值的和，目前设置为10MB upload.setSizeMax(1024 * 1024 * 10); try { //使用ServletFileUpload解析器解析上传数据，解析结果返回的是一个List List Iterator while (iterator.hasNext()) { FileItem item = iterator.next(); //判断jsp提交过来的是不是文件 if (item.isFormField()) { errorMessage = "请提交文件!"; break; } else { //文件名 String fileName = item.getName(); if (fileName == null || fileName.trim() == "") { System.out.println("文件名为空!"); } //处理不同浏览器提交的文件名带路径问题 fileName = fileName.substring(fileName.lastIndexOf("\\") + 1); //文件大小 Long fileSize = item.getSize(); //文件扩展名 String fileExtension = fileName.substring(fileName.lastIndexOf(".") + 1); //判断扩展名是否合法 if (!validExtension(fileExtension)) { errorMessage = "上传文件非法!"; item.delete(); break; } //获得文件输入流 InputStream in = item.getInputStream(); //得到保存文件的名称 String saveFileName = createFileName(fileName); //得到文件保存路径 String realFilePath = createRealFilePath(savePath, saveFileName); //创建文件输出流 FileOutputStream out = new FileOutputStream(realFilePath); //创建缓冲区 byte buffer[] = new byte[1024]; int len = 0; while ((len = in.read(buffer)) > 0) { //写文件 out.write(buffer, 0, len); } //关闭输入流 in.close(); //关闭输出流 out.close(); //删除临时文件 item.delete(); //将上传文件信息保存到附件表中 EntityAccessory entity = new EntityAccessory(); entity.setFileName(fileName); entity.setFileSize(fileSize); entity.setFile_ext_name(fileExtension); entity.setFilePath(realFilePath); AccessoryDao.add(entity); } } } catch (FileUploadBase.FileSizeLimitExceededException e) { e.printStackTrace(); errorMessage = "单个文件超出最大值!!!"; } catch (FileUploadBase.SizeLimitExceededException e) { e.printStackTrace(); errorMessage = "上传文件的总的大小超出限制的最大值!!!"; } catch (FileUploadException e) { e.printStackTrace(); errorMessage = "文件上传失败!!!"; } finally { if (!"".equals(errorMessage)) { request.setAttribute("errorMessage", errorMessage); request.getRequestDispatcher("pages/upload/error.jsp").forward(request, response); } else { response.sendRedirect("listUploadedFiles"); } } } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } private boolean validExtension(String fileExtension) { String[] exts = {"jpg", "txt", "doc", "pdf"}; for (int i = 0; i < exts.length; i++) { if (fileExtension.equals(exts[i])) { return true; } } return false; } private String createFileName(String fileName) { return UUID.randomUUID().toString() + "_" + fileName; } /** * 根据基本路径和文件名称生成真实文件路径，基本路径\\年\\月\\fileName * * @param basePath * @param fileName * @return */ private String createRealFilePath(String basePath, String fileName) { Calendar today = Calendar.getInstance(); String year = String.valueOf(today.get(Calendar.YEAR)); String month = String.valueOf(today.get(Calendar.MONTH) + 1); String upPath = basePath + File.separator + year + File.separator + month + File.separator; File uploadFolder = new File(upPath); if (!uploadFolder.exists()) { uploadFolder.mkdirs(); } String realFilePath = upPath + fileName; return realFilePath; } } 测试效果截图
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