Java分页技术的实现(一)

(一)创建一个web项目



(二)编写Java类

1.建立一个com.imooc.page包

package com.imooc.page;

public class Constant {

/**
* 男性
*/
public static final int GENDER_MALE = 1;

/**
* 女性
*/
public static final int GENDER_FEMALE = 2;

/**
* 默认每页显示多少条记录
*/
public static final int DEFAULT_PAGE_SIZE = 5;

/**
* 默认显示第几页记录
*/
public static final int DEFAULT_PAGE_NUM = 1;

/**
* 默认学生性别
*/
public static final int DEFAULT_GENDER = 0;
}

///////////////////////////////////////////////////////////
package com.imooc.page;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class EncodingFilter implements Filter {

@Override
public void destroy() {
// TODO Auto-generated method stub

}

@Override
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {

request.setCharacterEncoding("UTF-8");
response.setCharacterEncoding("UTF-8");
chain.doFilter(request,response);

}

@Override
public void init(FilterConfig arg0) throws ServletException {
// TODO Auto-generated method stub

}

}

2.创建一个com.imooc.page,model

package com.imooc.page.model;

import java.io.Serializable;
import java.util.List;

public class Pager<T> implements Serializable {

private static final long serialVersionUID = -8741766802354222579L;

private int pageSize; // 每页显示多少条记录

private int currentPage; //当前第几页数据

private int totalRecord; // 一共多少条记录

private int totalPage; // 一共多少页记录

private List<T> dataList; //要显示的数据

public Pager(int pageNum, int pageSize, List<T> sourceList){
if(sourceList == null || sourceList.isEmpty()){
return;
}

// 总记录条数
this.totalRecord = sourceList.size();

// 每页显示多少条记录
this.pageSize = pageSize;

//获取总页数
this.totalPage = this.totalRecord / this.pageSize;
if(this.totalRecord % this.pageSize !=0){
this.totalPage = this.totalPage + 1;
}

// 当前第几页数据
this.currentPage = this.totalPage < pageNum ?  this.totalPage : pageNum;

// 起始索引
int fromIndex   = this.pageSize * (this.currentPage -1);

// 结束索引
int toIndex  = this.pageSize * this.currentPage > this.totalRecord ? this.totalRecord : this.pageSize * this.currentPage;

this.dataList = sourceList.subList(fromIndex, toIndex);
}

public Pager(){

}

public Pager(int pageSize, int currentPage, int totalRecord, int totalPage,
List<T> dataList) {
super();
this.pageSize = pageSize;
this.currentPage = currentPage;
this.totalRecord = totalRecord;
this.totalPage = totalPage;
this.dataList = dataList;
}

public int getPageSize() {
return pageSize;
}

public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}

public int getCurrentPage() {
return currentPage;
}

public void setCurrentPage(int currentPage) {
this.currentPage = currentPage;
}

public int getTotalRecord() {
return totalRecord;
}

public void setTotalRecord(int totalRecord) {
this.totalRecord = totalRecord;
}

public int getTotalPage() {
return totalPage;
}

public void setTotalPage(int totalPage) {
this.totalPage = totalPage;
}

public List<T> getDataList() {
return dataList;
}

public void setDataList(List<T> dataList) {
this.dataList = dataList;
}

}

//////////////////////////////////////////////////////////
package com.imooc.page.model;

import java.io.Serializable;
import java.util.Map;

public class Student implements Serializable {

private static final long serialVersionUID = -7476381137287496245L;

private int id; //学生记录id

private String stuName;//学生姓名

private int age; //学生年龄

private int gender; //学生性别

private String address;//学生住址

public Student() {
super();
}

public Student(int id, String stuName, int age, int gender, String address) {
super();
this.id = id;
this.stuName = stuName;
this.age = age;
this.gender = gender;
this.address = address;
}

public Student(Map<String, Object> map){
this.id = (int)map.get("id");
this.stuName = (String)map.get("stu_name");
this.age = (int)map.get("age");
this.gender = (int)map.get("gender");
this.address = (String)map.get("address");
}

public int getId() {
return id;
}

public void setId(int id) {
this.id = id;
}

public String getStuName() {
return stuName;
}

public void setStuName(String stuName) {
this.stuName = stuName;
}

public int getAge() {
return age;
}

public void setAge(int age) {
this.age = age;
}

public int getGender() {
return gender;
}

public void setGender(int gender) {
this.gender = gender;
}

public String getAddress() {
return address;
}

public void setAddress(String address) {
this.address = address;
}

@Override
public String toString() {
return "Student [id=" + id + ", stuName=" + stuName + ", age=" + age
+ ", gender=" + gender + ", address=" + address + "]";
}

}

3.创建一个com.imooc.page.dao包

package com.imooc.page.dao;

import com.imooc.page.model.Pager;
import com.imooc.page.model.Student;

public interface StudentDao {

/**
* 根据查询条件，查询学生分页信息
*
* @param searchModel
*            封装查询条件
* @param pageNum
*            查询第几页数据
* @param pageSize
*            每页显示多少条记录
* @return 查询结果
*/
public Pager<Student> findStudent(Student searchModel, int pageNum,
int pageSize);
}
//////////////////////////////////////////////////////////////////
package com.imooc.page.dao;

import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import com.imooc.page.Constant;
import com.imooc.page.model.Pager;
import com.imooc.page.model.Student;
import com.imooc.page.util.JdbcUtil;

public class SublistStudentDaoImpl implements StudentDao {

@Override
public Pager<Student> findStudent(Student searchModel, int pageNum,
int pageSize) {
List<Student> allStudenList = getAllStudent(searchModel);

Pager<Student> pager = new Pager<Student>(pageNum, pageSize,
allStudenList);

return pager;
}

/**
* 模仿获取所有数据
*
* @param searchModel
*            查询参数
* @return 查询结果
*/
private static List<Student> getAllStudent(Student searchModel) {
List<Student> result = new ArrayList<Student>();
List<Object> paramList = new ArrayList<Object>();

String stuName = searchModel.getStuName();
int gender = searchModel.getGender();

StringBuilder sql = new StringBuilder(
"select * from t_student where 1=1");

if (stuName != null && !stuName.equals("")) {
sql.append(" and stu_name like ?");
paramList.add("%" + stuName + "%");
}

if (gender == Constant.GENDER_FEMALE || gender == Constant.GENDER_MALE) {
sql.append(" and gender = ?");
paramList.add(gender);
}

JdbcUtil jdbcUtil = null;
try {
jdbcUtil = new JdbcUtil();
jdbcUtil.getConnection(); // 获取数据库链接
List<Map<String, Object>> mapList = jdbcUtil.findResult(
sql.toString(), paramList);
if (mapList != null) {
for (Map<String, Object> map : mapList) {
Student s = new Student(map);
result.add(s);
}
}
} catch (SQLException e) {
throw new RuntimeException("查询所有数据异常！", e);
} finally {
if (jdbcUtil != null) {
jdbcUtil.releaseConn(); // 一定要释放资源
}
}

return result;
}

public static void main(String[] args) {
List<Student> lst = getAllStudent(new Student());
for (Student s : lst) {
System.out.println(s);
}
}
}

4.创建一个com.imooc.page.service包

package com.imooc.page.service;

import com.imooc.page.model.Pager;
import com.imooc.page.model.Student;

public interface StudentService {

/**
* 根据查询条件，查询学生分页信息
*
* @param searchModel
*            封装查询条件
* @param pageNum
*            查询第几页数据
* @param pageSize
*            每页显示多少条记录
* @return 查询结果
*/
public Pager<Student> findStudent(Student searchModel, int pageNum,
int pageSize);
}
////////////////////////////////////////////////////////////////
package com.imooc.page.service;

import com.imooc.page.dao.StudentDao;
import com.imooc.page.dao.SublistStudentDaoImpl;
import com.imooc.page.model.Pager;
import com.imooc.page.model.Student;

public class SublistStudentServiceImpl implements StudentService {

private StudentDao studentDao;

public SublistStudentServiceImpl() {
// 创建servivce实现类时，初始化dao对象。
studentDao = new SublistStudentDaoImpl();
}

@Override
public Pager<Student> findStudent(Student searchModel, int pageNum,
int pageSize) {
Pager<Student> result = studentDao.findStudent(searchModel, pageNum,
pageSize);
return result;
}

public StudentDao getStudentDao() {
return studentDao;
}

public void setStudentDao(StudentDao studentDao) {
this.studentDao = studentDao;
}
}

5.创建一个com.imooc.page.servlet包

package com.imooc.page.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.imooc.page.Constant;
import com.imooc.page.model.Pager;
import com.imooc.page.model.Student;
import com.imooc.page.service.StudentService;
import com.imooc.page.service.SublistStudentServiceImpl;
import com.imooc.page.util.StringUtil;

public class SublistServlet extends HttpServlet {

private static final long serialVersionUID = -3658128508633145268L;

private StudentService studentService = new SublistStudentServiceImpl();

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

doPost(request, response);
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// 接收request里的参数
String stuName = request.getParameter("stuName"); //学生姓名

// 获取学生性别
int gender = Constant.DEFAULT_GENDER;
String genderStr = request.getParameter("gender");
if(genderStr!=null && !"".equals(genderStr.trim())){
gender = Integer.parseInt(genderStr);
}

// 校验pageNum参数输入合法性
String pageNumStr = request.getParameter("pageNum");
if(pageNumStr !=null && !StringUtil.isNum(pageNumStr)){
request.setAttribute("errorMsg", "参数传输错误");
request.getRequestDispatcher("sublistStudent.jsp").forward(request, response);
return;
}

int pageNum = Constant.DEFAULT_PAGE_NUM; //显示第几页数据
if(pageNumStr!=null && !"".equals(pageNumStr.trim())){
pageNum = Integer.parseInt(pageNumStr);
}

int pageSize = Constant.DEFAULT_PAGE_SIZE;  // 每页显示多少条记录
String pageSizeStr = request.getParameter("pageSize");
if(pageSizeStr!=null && !"".equals(pageSizeStr.trim())){
pageSize = Integer.parseInt(pageSizeStr);
}

// 组装查询条件
Student searchModel = new Student();
searchModel.setStuName(stuName);
searchModel.setGender(gender);

//调用service 获取查询结果
Pager<Student> result = studentService.findStudent(searchModel,
pageNum, pageSize);

// 返回结果到页面
request.setAttribute("result", result);
request.setAttribute("stuName", stuName);
request.setAttribute("gender", gender);

request.getRequestDispatcher("sublistStudent.jsp").forward(request, response);
}

}

6.创建一个com.imooc.page.Util包

package com.imooc.page.util;

import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties;

public class JdbcUtil {

// 表示定义数据库的用户名
private static String USERNAME ;

// 定义数据库的密码
private static String PASSWORD;

// 定义数据库的驱动信息
private static String DRIVER;

// 定义访问数据库的地址
private static String URL;

// 定义数据库的链接
private Connection connection;

// 定义sql语句的执行对象
private PreparedStatement pstmt;

// 定义查询返回的结果集合
private ResultSet resultSet;

static{
//加载数据库配置信息，并给相关的属性赋值
loadConfig();
}

/**
* 加载数据库配置信息，并给相关的属性赋值
*/
public static void loadConfig() {
try {
InputStream inStream = JdbcUtil.class
.getResourceAsStream("/jdbc.properties");
Properties prop = new Properties();
prop.load(inStream);
USERNAME = prop.getProperty("jdbc.username");
PASSWORD = prop.getProperty("jdbc.password");
DRIVER= prop.getProperty("jdbc.driver");
URL = prop.getProperty("jdbc.url");
} catch (Exception e) {
throw new RuntimeException("读取数据库配置文件异常！", e);
}
}

public JdbcUtil() {

}

/**
* 获取数据库连接
*
* @return 数据库连接
*/
public Connection getConnection() {
try {
Class.forName(DRIVER); // 注册驱动
connection = DriverManager.getConnection(URL, USERNAME, PASSWORD); // 获取连接
} catch (Exception e) {
throw new RuntimeException("get connection error!", e);
}
return connection;
}

/**
* 执行更新操作
*
* @param sql
*            sql语句
* @param params
*            执行参数
* @return 执行结果
* @throws SQLException
*/
public boolean updateByPreparedStatement(String sql, List<?> params)
throws SQLException {
boolean flag = false;
int result = -1;// 表示当用户执行添加删除和修改的时候所影响数据库的行数
pstmt = connection.prepareStatement(sql);
int index = 1;
// 填充sql语句中的占位符
if (params != null && !params.isEmpty()) {
for (int i = 0; i < params.size(); i++) {
pstmt.setObject(index++, params.get(i));
}
}
result = pstmt.executeUpdate();
flag = result > 0 ? true : false;
return flag;
}

/**
* 执行查询操作
*
* @param sql
*            sql语句
* @param params
*            执行参数
* @return
* @throws SQLException
*/
public List<Map<String, Object>> findResult(String sql, List<?> params)
throws SQLException {
List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();
int index = 1;
pstmt = connection.prepareStatement(sql);
if (params != null && !params.isEmpty()) {
for (int i = 0; i < params.size(); i++) {
pstmt.setObject(index++, params.get(i));
}
}
resultSet = pstmt.executeQuery();
ResultSetMetaData metaData = resultSet.getMetaData();
int cols_len = metaData.getColumnCount();
while (resultSet.next()) {
Map<String, Object> map = new HashMap<String, Object>();
for (int i = 0; i < cols_len; i++) {
String cols_name = metaData.getColumnName(i + 1);
Object cols_value = resultSet.getObject(cols_name);
if (cols_value == null) {
cols_value = "";
}
map.put(cols_name, cols_value);
}
list.add(map);
}
return list;
}

/**
* 释放资源
*/
public void releaseConn() {
if (resultSet != null) {
try {
resultSet.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (pstmt != null) {
try {
pstmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}

public static void main(String[] args) {
JdbcUtil jdbcUtil = new JdbcUtil();
jdbcUtil.getConnection();
try {
List<Map<String, Object>> result = jdbcUtil.findResult(
"select * from t_student", null);
for (Map<String, Object> m : result) {
System.out.println(m);
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
jdbcUtil.releaseConn();
}
}
}
//////////////////////////////////////////////////////////////
package com.imooc.page.util;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class StringUtil {

/**
* 校验字符串是否是大于0的数字
* @param string
* @return
*/
public static boolean isNum(String string){
Pattern pattern = Pattern.compile("[1-9]{1}\\d*");
Matcher matcher = pattern.matcher(string);
return matcher.matches();
}
}

(三)在page项目文件夹下创建一个config文件夹，在config文件夹下创建jdbc.properties文件。

jdbc.username=root
jdbc.password=root
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/imooc

(四)在WebContext文件夹下创建sublist文件夹，在sublist文件夹下创建jsp页面。

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>学生信息</title>
</head>
<%
// 获取请求的上下文
String context = request.getContextPath();
%>
<script type="text/javascript">
// 当前第几页数据
var currentPage = ${result.currentPage};

// 总页数
var totalPage = ${result.totalPage};

function submitForm(actionUrl){
var formElement = document.getElementById("stuForm");
formElement.action = actionUrl;
formElement.submit();
}

// 第一页
function firstPage(){
if(currentPage == 1){
alert("已经是第一页数据");
return false;
}else{
submitForm("<%=context %>/sublist/SublistServlet?pageNum=1");
return true;
}
}

// 下一页
function nextPage(){
if(currentPage == totalPage){
alert("已经是最后一页数据");
return false;
}else{
submitForm("<%=context %>/sublist/SublistServlet?pageNum=" + (currentPage+1));
return true;
}
}

// 上一页
function previousPage(){
if(currentPage == 1){
alert("已经是第一页数据");
return false;
}else{
submitForm("<%=context %>/sublist/SublistServlet?pageNum=" + (currentPage-1));
return true;
}
}

// 尾页
function lastPage(){
if(currentPage == totalPage){
alert("已经是最后一页数据");
return false;
}else{
submitForm("<%=context %>/sublist/SublistServlet?pageNum=${result.totalPage}");
return true;
}
}
function initPage(){
var genderRequest = "${gender}" ;
var genderVal = 0;
var genderElement = document.getElementById("gender");
if(genderRequest != ""){
genderVal = parseInt(genderRequest);
}

var options = genderElement.options;
var i = 0;
for(i = 0; i < options.length; i++){
if(options[i].value == genderVal){
options[i].selected=true;
break;
}
}

}
</script>
<body onload="initPage();">
<div style="margin-left: 100px; margin-top: 100px;">
<div>
<font color="red">${errorMsg }</font>
</div>
<div>
<form action="<%=context %>/sublist/SublistServlet"   id="stuForm"  method="post">
姓名
<input type="text" name="stuName" id="stu_name" style="width:120px" value="${stuName }">
 
性别
<select name="gender" id="gender" style="width:80px">
<option value="0">全部</option>
<option value="1">男</option>
<option value="2">女</option>
</select>
  
<input type="submit" value="查询">
</form>
</div>
<br>
学生信息列表：<br>
<br>
<!-- 后台返回结果为空 -->
<c:if test="${fn:length(result.dataList) eq 0 }">
<span>查询的结果不存在</span>
</c:if>

<!-- 后台返回结果不为空 -->
<c:if test="${fn:length(result.dataList) gt 0 }">
<table border="1px" cellspacing="0px"
style="border-collapse: collapse">
<thead>
<tr height="30">
<th width="130">姓名</th>
<th width="130">性别</th>
<th width="130">年龄</th>
<th width="190">家庭地址</th>
</tr>
</thead>
<c:forEach items="${result.dataList }" var="student">
<tr>
<td><c:out value="${student.stuName }"></c:out></td>
<td>
<c:if test="${ student.gender eq 1}">男</c:if>
<c:if test="${ student.gender eq 2}">女</c:if>
</td>
<td><c:out value="${student.age }"></c:out></td>
<td><c:out value="${student.address }"></c:out></td>
</tr>
</c:forEach>
</table>
<br> 共${result.totalRecord }条记录共${result.totalPage }页  当前第${result.currentPage }页  
<a href="#" onclick="firstPage();">首页</a>  
<a href="#" onclick="nextPage();">下一页</a>  
<a href="#" onclick="previousPage();">上一页</a>  
<a href="#" onblur="lastPage();">尾页</a>
</c:if>
</div>
</body>
</html>

(五)在WEB-INF文件夹下创建一个lib文件夹导入相关jar包。

(六)在WEB-INF文件夹下创建一个web.xml配置文件

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>pager</display-name>
<filter>
<filter-name>EncodingFilter</filter-name>
<filter-class>com.imooc.page.EncodingFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>EncodingFilter</filter-name>
<url-pattern>*</url-pattern>
</filter-mapping>
<servlet>
<servlet-name>SublistServlet</servlet-name>
<servlet-class>com.imooc.page.servlet.SublistServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>SublistServlet</servlet-name>
<url-pattern>/sublist/SublistServlet</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>

(七)创建数据库

CREATE TABLE `t_student` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`stu_name` varchar(16) NOT NULL,
`gender` int(11) DEFAULT NULL,
`age` int(11) DEFAULT NULL,
`address` varchar(128) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=12 DEFAULT CHARSET=utf8;

-- Records of t_student
-- ----------------------------
INSERT INTO `t_student` VALUES ('1', '王小军', '1', '17', '北京市东城区');
INSERT INTO `t_student` VALUES ('2', '李雷雷', '1', '16', '北京市朝阳区');
INSERT INTO `t_student` VALUES ('3', '张静', '2', '16', '北京市昌平区');
INSERT INTO `t_student` VALUES ('4', '王晓萌', '2', '17', '北京市顺义区');
INSERT INTO `t_student` VALUES ('5', '韩梅梅', '2', '16', '北京市朝阳区');
INSERT INTO `t_student` VALUES ('6', '李小军', '1', '17', '北京市海淀区');
INSERT INTO `t_student` VALUES ('7', '成龙', '1', '16', '北京市石景山区');
INSERT INTO `t_student` VALUES ('8', '李海飞', '2', '16', '北京市海淀区');
INSERT INTO `t_student` VALUES ('9', '罗红', '2', '16', '北京市朝阳区');
INSERT INTO `t_student` VALUES ('10', '孙海杰', '1', '16', '北京市石景山区');
INSERT INTO `t_student` VALUES ('11', '王海龙', '1', '16', '北京市东城区');

(八)演示结果