servlet paging code example
- 2020-11-18 06:23:53
- OfStack
1. First create an object, UserData, to hold the data obtained from the database.
package com.tool;
import java.math.BigDecimal;
import java.util.Date;
/**
* Created by lx_sunwei on 14-1-6.
*/
public class UserData {
/**
* EMP Data properties in a table
*/
private String ename;
private String job;
private BigDecimal empno;
private BigDecimal mgr;
private Date hireDate;
private BigDecimal sal;
private BigDecimal comm;
private BigDecimal deptno;
public BigDecimal getEmpno() {
return empno;
}
public void setEmpno(BigDecimal empno) {
this.empno = empno;
}
public BigDecimal getMgr() {
return mgr;
}
public void setMgr(BigDecimal mgr) {
this.mgr = mgr;
}
public Date getHireDate() {
return hireDate;
}
public void setHireDate(Date hireDate) {
this.hireDate = hireDate;
}
public BigDecimal getSal() {
return sal;
}
public void setSal(BigDecimal sal) {
this.sal = sal;
}
public BigDecimal getComm() {
return comm;
}
public void setComm(BigDecimal comm) {
this.comm = comm;
}
public BigDecimal getDeptno() {
return deptno;
}
public void setDeptno(BigDecimal deptno) {
this.deptno = deptno;
}
public String getEname() {
return ename;
}
public void setEname(String ename) {
this.ename = ename;
}
public String getJob() {
return job;
}
public void setJob(String job) {
this.job = job;
}
}
Create an DBHelper object to interact with the database
package com.dao;
import com.tool.UserData;
import java.math.BigDecimal;
import java.sql.*;
import java.util.*;
import java.util.Date;
/**
* Created by lx_sunwei on 14-1-6.
*/
public class DBHelper {
Connection conn; // Database connection object
PreparedStatement pt; //SQL Statement preprocessing object
ResultSet rs; // Result set object
public DBHelper(){
try {
Class.forName("oracle.jdbc.driver.OracleDriver"); // Load the driver
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
/**
* Gets the data for the current page
* @param curPage
* @param rowsPerPage
* @return
*/
public List<UserData> getData(int curPage, int rowsPerPage) {
List<UserData> dataList = new ArrayList<>();
String url = "jdbc:oracle:thin:@localhost:1521:orcl";
try {
conn = DriverManager.getConnection(url,"scott","tiger");
String sql = "select * from emp where rownum <= ((? - 1) * "+rowsPerPage+" + "+rowsPerPage+") minus " +
" select * from emp where rownum <= (? - 1) * "+rowsPerPage+" ";
pt = conn.prepareStatement(sql);
pt.setInt(1,curPage);
pt.setInt(2,curPage);
rs = pt.executeQuery();
while (rs.next()){
/**
* Get the data from the result set
*/
UserData userData = new UserData();
BigDecimal empno = rs.getBigDecimal("empno");
String ename = rs.getString("ename");
String job = rs.getString("job");
BigDecimal mgr = rs.getBigDecimal("mgr");
Date hireDate = rs.getDate("hiredate");
BigDecimal sal = rs.getBigDecimal("sal");
BigDecimal comm = rs.getBigDecimal("comm");
BigDecimal deptno = rs.getBigDecimal("deptno");
/**
* Set object properties
*/
userData.setEmpno(empno);
userData.setEname(ename);
userData.setJob(job);
userData.setMgr(mgr);
userData.setHireDate(hireDate);
userData.setSal(sal);
userData.setComm(comm);
userData.setDeptno(deptno);
dataList.add(userData); // Add an object to a collection
}
rs.close();
pt.close();
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
return dataList;
}
/**
* Total number of pages returned
* @return
*/
public int getMaxPage(int rowsPerPage) {
int maxPage;
int maxRowCount = 0;
String url = "jdbc:oracle:thin:@localhost:1521:orcl";
try {
conn = DriverManager.getConnection(url,"scott","tiger"); // Creating a database connection
String sql = "select count(*) from emp";
pt = conn.prepareStatement(sql);
rs = pt.executeQuery();
if (rs.next()){
maxRowCount = rs.getInt(1); // Total number of rows
}
} catch (SQLException e) {
e.printStackTrace();
}
maxPage = (maxRowCount + rowsPerPage - 1) / rowsPerPage; // Total number of pages
return maxPage;
}
}
3. Create Servlet to control the display page
package com.servlet;
import com.dao.DBHelper;
import com.tool.UserData;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.*;
/**
* Created by lx_sunwei on 14-1-6.
*/
public class Servlet extends HttpServlet {
public int rowsPerPage; // The number of rows displayed per page
public int curPage; // Current page number
public int maxPage; // A total number of pages
DBHelper db = new DBHelper();
public Servlet(){
rowsPerPage = 5;
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String curPage1 = request.getParameter("page"); // Gets the current page number
if (curPage1 == null){
curPage = 1;
request.setAttribute("curPage",curPage); // Set up the curPage object
}else {
curPage = Integer.parseInt(curPage1);
if (curPage < 1){
curPage = 1;
}
request.setAttribute("curPage",curPage);
}
List<UserData> dataList;
dataList = db.getData(curPage,rowsPerPage); // Gets the data for the current page
maxPage = db.getMaxPage(rowsPerPage); // Get total pages
request.setAttribute("dataList",dataList);
request.setAttribute("maxPage", maxPage);
RequestDispatcher rd = request.getRequestDispatcher("pagemain.jsp"); // Forward the request to pagemain.jsp page
rd.forward(request,response);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request,response);
}
}
4. Create JSP page to display data.
<%@ page import="java.util.List" %>
<%@ page import="com.tool.UserData" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>servlet Data paging </title>
<link rel="stylesheet" type="text/css" href="css.css">
</head>
<body>
<div style="margin-top: 15%; margin-left: 25%">
<table>
<caption>SCOTT The user, EMP Data in a table </caption>
<%! int curPage,maxPage; %>
<% curPage =Integer.parseInt(request.getAttribute("curPage").toString()); %> <!-- Get current page -->
<% maxPage =Integer.parseInt((String)request.getAttribute("maxPage").toString()); %> <!-- Get total pages -->
<%if (request.getAttribute("dataList") == null){
%>
<tr>
<td colspan="8"> There is no data </td>
</tr>
<%
}else {
%>
<tr>
<!-- header -->
<th>EMPNO</th>
<th>ENAME</th>
<th>JOB</th>
<th>MGR</th>
<th>HIREDATE</th>
<th>SAL</th>
<th>COMM</th>
<th>DEPTNO</th>
</tr>
<%
List list = (List) request.getAttribute("dataList");
for (Object aList : list) {
UserData userData = (UserData) aList;
%>
<tr>
<!-- Get the data in the table -->
<td><%= userData.getEmpno() %></td>
<td><%= userData.getEname() %></td>
<td><%= userData.getJob() %></td>
<td><%= userData.getMgr() %></td>
<td><%= userData.getHireDate() %></td>
<td><%= userData.getSal() %></td>
<td><%= userData.getComm() %></td>
<td><%= userData.getDeptno() %></td>
</tr>
<%
}
}
%>
</table>
</div>
<div style="margin-top: 8%; margin-left: 29%">
The first <%= curPage %> Page, <%= maxPage %> page
<%if (curPage > 1){
%>
<a href="Servlet?page=1"> Home page </a>
<a href="Servlet?page=<%=curPage - 1%>"> on 1 page </a>
<%
}else {
%>
Home page on 1 page
<%
}%>
<%if (curPage < maxPage){
%>
<a href="Servlet?page=<%=curPage + 1%>"> Under the 1 page </a>
<a href="Servlet?page=<%=maxPage %>"> back </a>
<%
}else {
%>
Under the 1 page back
<%
}%>
Go to the first <form name="form1" action="Servlet" method="get">
<label>
<select name="page" onchange="document.form1.submit()">
<%for ( int i = 1; i <= maxPage; i++){
if (i == curPage){
%>
<!-- The current page number is selected by default -->
<option selected value="<%= i%>"><%= i %></option>
<%
}else {
%>
<option value="<%= i %>"><%= i %></option>
<%
}
}%>
</select>
</label>
</form> page
</div>
</body>
</html>
The configuration file in ES25en. xml is:
<?xml version="1.0" encoding="UTF-8"?>
<web-app 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_3_0.xsd"
version="3.0">
<servlet>
<servlet-name>Servlet</servlet-name>
<servlet-class>com.servlet.Servlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Servlet</servlet-name>
<url-pattern>/Servlet</url-pattern>
</servlet-mapping>
</web-app>
The project deployment to Tomcat server, enter the address: http: / / localhost: 8080 / Servlet so you can see the effect