package util; import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement; public class DB {    private DB() {     }     static {       try {           Class.forName("oracle.jdbc.OracleDriver");       } catch (ClassNotFoundException e) {           e.printStackTrace();       }    }     public static Connection getConnection() {       Connection con = null;       try {           con = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:orcl","wt", "wt");       } catch (SQLException e) {           e.printStackTrace();       }       return con;    }     public static void closeConnection(Connection con) {       if (con != null) {           try {              con.close();              con = null;           } catch (SQLException e) {              e.printStackTrace();           }       }    }        public static Statement getStatement(Connection con){       Statement statement=null;       try {           statement=con.createStatement();       } catch (SQLException e) {           e.printStackTrace();       }       return statement;    }       public static void closeStatement(Statement statement) {       if (statement != null) {           try {              statement.close();              statement = null;           } catch (SQLException e) {              e.printStackTrace();           }       }    }        public static PreparedStatement getPreparedStatement(Connection con,String sql){       PreparedStatement preparedStatement=null;       try {           preparedStatement=con.prepareStatement(sql);       } catch (SQLException e) {           e.printStackTrace();       }       return preparedStatement;    }       /*     * isGeneratedKey:是否获得记录的主键     * Statement.RETURN_GENERATED_KEYS:是否获得记录的主键     * */    public static PreparedStatement getPreparedStatement(Connection con,String sql,boolean isGeneratedKey){        PreparedStatement preparedStatement=null;       try {           if(isGeneratedKey==true){              String generatedColumns[] = {"id"};  //该表的主键              preparedStatement=con.prepareStatement(sql,generatedColumns);           }       } catch (SQLException e) {           e.printStackTrace();       }       return preparedStatement;    }    public static void closePreparedStatement(PreparedStatement preparedStatement) {       if (preparedStatement != null) {           try {              preparedStatement.close();              preparedStatement = null;           } catch (SQLException e) {              e.printStackTrace();           }       }    }    public static ResultSet executeQuery(Statement statement,String sql){       ResultSet resultSet=null;       try {           resultSet=statement.executeQuery(sql);       } catch (SQLException e) {           e.printStackTrace();       }       return resultSet;    }    public static void executeUpdate(String sql){       Connection con=DB.getConnection();       PreparedStatement ps=DB.getPreparedStatement(con, sql);       try {           ps.executeUpdate(sql);       } catch (SQLException e) {           e.printStackTrace();       }finally{           DB.closePreparedStatement(ps);           DB.closeConnection(con);       }    }    public static void closeResultSet(ResultSet resultSet){       if(resultSet!=null){           try {              resultSet.close();               resultSet=null;           } catch (SQLException e) {              e.printStackTrace();           }       }    }}

package dao;import java.sql.Connection;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;import java.util.ArrayList;import java.util.List;import model.User;import util.DB; public class UserOracleDAO {        public List<User> getPage(int pageNumber, int pageSize) {       Connection con = DB.getConnection();       String sql = "";       if (pageNumber == 0) {  //如果第一页的话           pageNumber = 1;           sql += "select * from(select a.*, rownum r from( select  * from t_user) a where rownum <="                  + pageSize + ") B where r >=" + pageNumber + "";       } else {           pageNumber += 1;           sql += "select * from(select a.*, rownum r from( select  * from t_user) a where rownum <="                  + pageNumber                  * pageSize                  + ") B where r >"                  + ((pageNumber * pageSize) - pageSize) + "";       }       Statement st = null;       ResultSet rs = null;       List<User> users = new ArrayList<User>();       try {           st = con.createStatement();           rs = st.executeQuery(sql);           while (rs.next()) {              User user = new User();              user.setUsername(rs.getString("username"));              user.setPassword(rs.getString("password"));              users.add(user);           }       } catch (SQLException e) {           e.printStackTrace();       } finally {           DB.closeResultSet(rs);           DB.closeStatement(st);           DB.closeConnection(con);       }       return users;    }     public int getCounts() {       Connection con = DB.getConnection();       Statement st = DB.getStatement(con);       String sql = "select count(*) from t_user";       ResultSet rs = null;       int count = 0;       try {           rs = st.executeQuery(sql);           if (rs.next()) {              count = rs.getInt("count(*)");           }       } catch (SQLException e) {           e.printStackTrace();       }       return count;    }     //获得首页    public List<User> getFirstPage(int pageSize) {       Connection con = DB.getConnection();       int start=1;       String sql = "select * from(select a.*, rownum r from( select  * from t_user) a where rownum <="           + pageSize + ") B where r >=" +start+ "";       Statement st = null;       ResultSet rs = null;       List<User> users = new ArrayList<User>();       try {           st = con.createStatement();           rs = st.executeQuery(sql);           while (rs.next()) {              User user = new User();              user.setUsername(rs.getString("username"));              user.setPassword(rs.getString("password"));              users.add(user);           }       } catch (SQLException e) {           e.printStackTrace();       } finally {           DB.closeResultSet(rs);           DB.closeStatement(st);           DB.closeConnection(con);       }       return users;    }    //获得首页    public List<User> getLastPage(int pageCount,int pageSize) {       Connection con = DB.getConnection();       int start=((pageCount*pageSize)-pageSize)+1;       int end=(pageCount*pageSize)+1;       String sql = "select * from(select a.*, rownum r from( select  * from t_user) a where rownum <="           + end + ") B where r >=" +start+ "";       Statement st = null;       ResultSet rs = null;       List<User> users = new ArrayList<User>();       try {           st = con.createStatement();           rs = st.executeQuery(sql);           while (rs.next()) {              User user = new User();              user.setUsername(rs.getString("username"));              user.setPassword(rs.getString("password"));              users.add(user);           }       } catch (SQLException e) {           e.printStackTrace();       } finally {           DB.closeResultSet(rs);           DB.closeStatement(st);           DB.closeConnection(con);       }       return users;    }}

package model; import java.io.Serializable; public class User implements Serializable{    private String username;    private String password;    public String getUsername() {       return username;    }    public void setUsername(String username) {       this.username = username;    }    public String getPassword() {       return password;    }    public void setPassword(String password) {       this.password = password;    }}

package servlet; import java.io.IOException;import java.util.List; import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession; import model.User;import dao.UserOracleDAO; public class UserServlet extends HttpServlet {    private static final long serialVersionUID = 1L;     public void doGet(HttpServletRequest request, HttpServletResponse response)           throws ServletException, IOException {       doPost(request, response);    }     public void doPost(HttpServletRequest request, HttpServletResponse response)           throws ServletException, IOException {       String method=request.getParameter("method");       UserOracleDAO uod=new UserOracleDAO();        HttpSession session=request.getSession();       int pageSize=5;       int userSize=uod.getCounts(); //获得所有记录        int pageCount=userSize/pageSize==0?userSize/pageSize:userSize/pageSize+1; //判断是否整除,页数是否是整数       if(method.equals("first")){           int currentPage=Integer.parseInt(request.getParameter("currentPage"));           List<User> users=uod.getFirstPage(pageSize);           session.setAttribute("list",users);           session.setAttribute("currentPage",String.valueOf(currentPage));           session.setAttribute("pageCount",String.valueOf(pageCount));           getServletConfig().getServletContext().getRequestDispatcher("/list.jsp").forward(request,response);           return;       }       if(method.equals("last")){           int currentPage=pageCount;           List<User> users=uod.getLastPage(pageCount, pageSize);           session.setAttribute("list",users);           session.setAttribute("currentPage",String.valueOf(currentPage));           session.setAttribute("pageCount",String.valueOf(pageCount));           getServletConfig().getServletContext().getRequestDispatcher("/list.jsp").forward(request,response);           return;       }       if(method.equals("back")){           int currentPage=Integer.parseInt(request.getParameter("currentPage"));           if(currentPage!=0){              currentPage--;              List<User> users=uod.getPage(currentPage,pageSize);              session.setAttribute("list",users);              session.setAttribute("currentPage",String.valueOf(currentPage));              session.setAttribute("pageCount",String.valueOf(pageCount));               getServletConfig().getServletContext().getRequestDispatcher("/list.jsp").forward(request,response);           }           return;       }       if(method.equals("next")){           int currentPage=Integer.parseInt(request.getParameter("currentPage"));           currentPage++;           List<User> users=uod.getPage(currentPage,pageSize);           session.setAttribute("list",users);           session.setAttribute("currentPage",String.valueOf(currentPage));           session.setAttribute("pageCount",String.valueOf(pageCount));           getServletConfig().getServletContext().getRequestDispatcher("/list.jsp").forward(request,response);           return;       }    }}

<?xml version="1.0" encoding="UTF-8"?><web-app version="2.5"     xmlns="http://java.sun.com/xml/ns/javaee"     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee     http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">  <servlet>    <description>This is the description of my J2EE component</description>    <display-name>This is the display name of my J2EE component</display-name>    <servlet-name>UserServlet</servlet-name>    <servlet-class>servlet.UserServlet</servlet-class>  </servlet>   <servlet-mapping>    <servlet-name>UserServlet</servlet-name>    <url-pattern>/UserServlet</url-pattern>  </servlet-mapping>  <welcome-file-list>    <welcome-file>index.jsp</welcome-file>  </welcome-file-list></web-app>

<%@ page language="java"    import="java.util.*,model.User,dao.UserOracleDAO"    pageEncoding="GB18030"%><%    String path = request.getContextPath();    String basePath = request.getScheme() + "://"           + request.getServerName() + ":" + request.getServerPort()           + path + "/";%><%    List<User> users = (List<User>) session.getAttribute("list");    int currentPage=0;  //当前页    int PageCount=0; //总页数    int pageSize=5;  //每页显示数据数     if (users != null) {       currentPage=Integer.parseInt((String)session.getAttribute("currentPage"));       PageCount=Integer.parseInt((String)session.getAttribute("pageCount"));    } else {       currentPage=0;       UserOracleDAO uod = new UserOracleDAO();       users = uod.getFirstPage(pageSize);       int userSize=uod.getCounts();       PageCount=userSize/pageSize==0?userSize/pageSize:userSize/pageSize+1; //判断是否整除,页数是否是整数    }%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>    <head>       <base href="http://www.mamicode.com/">        <title>My JSP ‘index.jsp‘ starting page</title>       <meta http-equiv="pragma" content="no-cache">       <meta http-equiv="cache-control" content="no-cache">       <meta http-equiv="expires" content="0">       <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">       <meta http-equiv="description" content="This is my page">       <!--    <link rel="stylesheet" type="text/css" href="http://www.mamicode.com/styles.css">    -->    </head>     <body>       <table border=‘1‘>           <tr>              <td>                  用户名              </td>              <td>                  密码              </td>           </tr>           <%              for (Iterator<User> it = users.iterator(); it.hasNext();) {                  User user = it.next();           %>           <tr>              <td><%=user.getUsername()%></td>              <td><%=user.getPassword()%></td>           </tr>           <%              }           %>           <tr>              <td>                  <a href="http://www.mamicode.com/UserServlet?method=first¤tPage=0">首页</a>                  <a href="http://www.mamicode.com/UserServlet?method=back¤tPage=">上一页</a>                  <%if(currentPage==0){ %>                  <a>1/<%=PageCount%></a>                  <%}else if(currentPage==PageCount){%>                      <a><%=PageCount%>/<%=PageCount%></a>                  <%}else{ %>                      <a><%=currentPage+1%>/<%=PageCount%></a>                  <%}%>                  <a href="http://www.mamicode.com/UserServlet?method=next¤tPage=">下一页</a>                  <a href="http://www.mamicode.com/UserServlet?method=last">尾页</a>              </td>           </tr>        </table>    </body></html>