一.开发图示
1.1图解
1.2包图
二.代码实现
需求：实现分页查询
2.1JavaBean
package work.itcase.entity;
/**
* javaBean 实体类
* @author Administrator
*
*/
public class Employee {
private int empId; // 员工id
private String empName; // 员工名称
private int deptid; // 部门id
public int getEmpId() {
return empId;
}
public void setEmpId(int empId) {
this.empId = empId;
}
public String getEmpName() {
return empName;
}
public void setEmpName(String empName) {
this.empName = empName;
}
public int getDeptid() {
return deptid;
}
public void setDeptid(int deptid) {
this.deptid = deptid;
}
public Employee(int empId,String empName, int deptid) {
super();
this.empId = empId;
this.empName = empName;
this.deptid = deptid;
}
public Employee() {
}
@Override
public String toString() {
return "Employee [empId=" + empId + ", empName=" + empName
+ ", deptid=" + deptid + "]";
}
}2.2dao数据访问层接口
package work.itcase.dao;
import work.itcase.entity.Employee;
import work.itcase.utils.PageBean;
/**
* 数据访问层
* @author Administrator
*
*/
public interface EmployeeDao {
/* 分页查询数据 */
public void getAll(PageBean<Employee> pb);
/* 查询总记录 */
public int getTotalCount();
}2.3分页参数的封装
package work.itcase.utils;
import java.util.List;
/**
* 分页参数的封装
*
* @author Administrator
*
* @param <T>
*/
public class PageBean<T> {
private int currentPage = 1; // 当前页，默认显示第一页
private int pageCount = 4; // 每页显示的行数(查询返回的行数), 默认每页显示4行
private int totalCount; // 总记录数
private int totalPage; // 总页数 = 总记录数 / 每页显示的行数 (+ 1)
private List<T> pageData;
public int getCurrentPage() {
return currentPage;
}
public void setCurrentPage(int currentPage) {
this.currentPage = currentPage;
}
// 返回总页数
public int getTotalpage() {
if (totalCount % pageCount == 0) {
totalPage = totalCount / pageCount;
} else {
totalPage = totalCount / pageCount + 1;
}
return totalPage;
}
public void setTotalPage(int totalPage) {
this.totalPage = totalPage;
}
public int getPageCount() {
return pageCount;
}
public void setPageCount(int pageCount) {
this.pageCount = pageCount;
}
public int getTotalCount() {
return totalCount;
}
public void setTotalCount(int totalCount) {
this.totalCount = totalCount;
}
public List<T> getPageData() {
return pageData;
}
public void setPageData(List<T> pageData) {
this.pageData = pageData;
}
public int getTotalPage() {
return totalPage;
}
}2.4dao数据访问层接口实现
package work.itcase.daoimpl;
import java.sql.SQLException;
import java.util.List;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;
import work.itcase.dao.EmployeeDao;
import work.itcase.entity.Employee;
import work.itcase.utils.JdbcUtils;
import work.itcase.utils.PageBean;
/**
* 数据访问层实现
*
* @author Administrator
*
*/
public class EmployeeDaoImpl implements EmployeeDao {
@Override
public void getAll(PageBean<Employee> pb) {
// 1. 查询总记录； 设置到pb对象中
int totalCount = this.getTotalCount();
pb.setTotalCount(totalCount);
/*
* 分页查询 考虑因素 1.当前页面是首页点击 上一页 报错 2.当前页面是末页点击 下一页 报错
*
* 解决 ： 1.如果当前页<= 0; 当前页面设置为1 2.如果当前页面>最大页面数； 将当前页面设置为最大页数
*/
// 判断
if (pb.getCurrentPage() <= 0) {
pb.setCurrentPage(1); // 把当前页设置为1
} else if (pb.getCurrentPage() > pb.getTotalPage()) {
// 把当前页设置为最大页数
pb.setCurrentPage(pb.getTotalPage());
}
// 2. 获取当前页： 计算查询的起始行、返回的行数
int currentPage = pb.getCurrentPage();
int index = (currentPage - 1) * pb.getPageCount(); // 查询的起始行
int count = pb.getPageCount(); // 查询返回的行数
try {
// 3.分页查询数据; 把查询到的数据设置到pb对象中
String sql = "select * from employee limit ?,?";
// 得到QueryRunner对象
QueryRunner qr = JdbcUtils.getQueryRuner();
// 根据当前页，查询当前页数据(一页数据)
List<Employee> pageData = qr
.query(sql, new BeanListHandler<Employee>(Employee.class),
index, count);
// 设置到对象中
pb.setPageData(pageData);
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException(e);
}
}
@Override
public int getTotalCount() {
String sql = "select count(*) from employee";
try {
// 创建QueryRunner对象
QueryRunner qr = JdbcUtils.getQueryRuner();
// 执行查询， 返回结果的第一行的第一列
Long count = qr.query(sql, new ScalarHandler<Long>());
return count.intValue();
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}2.5业务逻辑层接口
package work.itcase.service;
import work.itcase.entity.Employee;
import work.itcase.utils.PageBean;
/**
* 业务逻辑层接口设计
* @author Administrator
*
*/
public interface EmployeeService {
/**
* 分页查询数据
*/
public void getAll(PageBean<Employee> pb);
}2.6业务逻辑层j接口实现
package work.itcase.serviceimpl;
import work.itcase.dao.EmployeeDao;
import work.itcase.daoimpl.EmployeeDaoImpl;
import work.itcase.entity.Employee;
import work.itcase.service.EmployeeService;
import work.itcase.utils.PageBean;
/**
* 业务逻辑层实现
*
* @author Administrator
*
*/
public class EmployeeServiceImpl implements EmployeeService {
// 创建dao实例
private EmployeeDao employ = new EmployeeDaoImpl();
@Override
public void getAll(PageBean<Employee> pb) {
try {
employ.getAll(pb);
} catch (Exception e) {
e.printStackTrace();
throw new RuntimeException(e);
}
}
}2.7控制器
package work.itcase.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 work.itcase.entity.Employee;
import work.itcase.service.EmployeeService;
import work.itcase.serviceimpl.EmployeeServiceImpl;
import work.itcase.utils.PageBean;
/**
* 4.开发控制器
* @author Administrator
*
*/
public class IndexServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
// 1.创建Service实例
private EmployeeService service = new EmployeeServiceImpl();
// 跳转资源
private String uri;
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// 设置编码格式
request.setCharacterEncoding("utf-8");
try {
// 1.获取 当前页面 参数：(第一次访问当前页为null)
String currPage = request.getParameter(" currPage");
// 判断
if (currPage == null || "".equals(currPage.trim())) {
currPage = "1"; // 第一次访问，设置当前页为1;
}
// 转换
int currentPage = Integer.parseInt(currPage);
// 2. 创建PageBean对象，设置当前页参数； 传入service方法参数
PageBean<Employee> pageBean = new PageBean<Employee>();
pageBean.setCurrentPage(currentPage);
// 3. 调用service
service.getAll(pageBean); // 【pageBean已经被dao填充了数据】
// 4. 保存pageBean对象，到request域中
request.setAttribute("pageBean", pageBean);
// 5. 跳转
uri = "/WEB-INF/list.jsp";
} catch (NumberFormatException e) {
e.printStackTrace();
// 出现错误，跳转到错误页面；给用户友好提示
uri = "/error/error.jsp";
}
request.getRequestDispatcher(uri).forward(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doGet(request, response);
}
}2.8Jdbc工具类
package work.itcase.utils;
import javax.sql.DataSource;
import org.apache.commons.dbutils.QueryRunner;
import com.mchange.v2.c3p0.ComboPooledDataSource;
/**
* 工具类 1.初始化c3p0连接池 2.创建Dbutils核心工具对象
*
* @author Administrator
*/
public class JdbcUtils {
/*
* 1.初始化池c3p0连接池
*/
private static DataSource dataSource;
static {
dataSource = new ComboPooledDataSource();
}
/*
* 2.创建Dbutils核心工具类对象
*/
public static QueryRunner getQueryRuner() {
/*
* 创建QueryRunner对象，传入连接池对象
* 在创建QueryRunner对象的时候，如果传入了数据源对象；
* 那么在使用QueryRunner对象方法的时候，就不需要传入连接对象；
* 会自动从数据源中获取连接(不用关闭连接)
*/
return new QueryRunner(dataSource);
}
}2.9c3p0连接池
<c3p0-config>
<default-config>
<!--连接数据库 -->
<property name="jdbcUrl">jdbc:mysql://localhost:3306/demo01?characterEncoding=utf8
</property>
<!--数据库驱动-->
<property name="driverClass">com.mysql.jdbc.Driver</property>
<!--用户名。Default: null -->
<property name="user">root</property>
<!--密码。Default: null -->
<property name="password">0000</property>
<!--初始化时获取三个连接，取值应在minPoolSize与maxPoolSize之间。Default: 3 -->
<property name="initialPoolSize">3</property>
<!--连接池中保留的最大连接数。Default: 15 -->
<property name="maxPoolSize">6</property>
<!--最大空闲时间,60秒内未使用则连接被丢弃。若为0则永不丢弃。Default: 0 -->
<property name="maxIdleTime">1000</property>
</default-config>
<named-config name="oracle_config">
<property name="jdbcUrl">jdbc:mysql://localhost:3306/demo01?characterEncoding=utf8</property>
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="user">root</property>
<property name="password">0000</property>
<property name="initialPoolSize">3</property>
<property name="maxPoolSize">6</property>
<property name="maxIdleTime">1000</property>
</named-config>
</c3p0-config>2.10 jsp页面
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<!-- 引入jstl核心标签库 -->
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>分页查询数据</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">
</head>
<body>
<body>
<table border="1" width="80%" align="center" cellpadding="5" cellspacing="0">
<tr>
<td>序号</td>
<td>员工编号</td>
<td>员工姓名</td>
</tr>
<!-- 迭代数据 -->
<c:choose>
<c:when test="${not empty requestScope.pageBean.pageData}">
<!-- ${not empty requestScope.pageBean.pageData}
not empty:不为空
requestScope:使用El表达输出数据类型
从四个域获取:${pageBean}
从指定域获取： ${pageScope.pageBean}
域范围： pageScoep / requestScope / sessionScope / applicationScope
-->
<c:forEach var="emp" items="${requestScope.pageBean.pageData}" varStatus="vs">
<tr>
<td>${vs.count }</td>
<td>${emp.empId }</td>
<td>${emp.empName }</td>
</tr>
</c:forEach>
</c:when>
<c:otherwise>
<tr>
<td colspan="3">对不起，没有你要找的数据</td>
</tr>
</c:otherwise>
</c:choose>
<tr>
<td colspan="3" align="center">
当前${requestScope.pageBean.currentPage }/${requestScope.pageBean.totalPage }页
<a href="${pageContext.request.contextPath }/index?currentPage=1">首页</a>
<a href="${pageContext.request.contextPath }/index?currentPage=${requestScope.pageBean.currentPage-1}">上一页 </a>
<a href="${pageContext.request.contextPath }/index?currentPage=${requestScope.pageBean.currentPage+1}">下一页 </a>
<a href="${pageContext.request.contextPath }/index?currentPage=${requestScope.pageBean.totalPage}">末页</a>
</td>
</tr>
</table>
</body>
</html>2.11数据库
/*建库代码*/
CREATE DATABASE demo01 DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci
/*建表代码*/
CREATE TABLE dept( /*主表*/
deptid INT PRIMARY KEY AUTO_INCREMENT,
deptName VARCHAR(16) NOT NULL
)
CREATE TABLE employee(/*从表*/
empId INT PRIMARY KEY AUTO_INCREMENT,
empName VARCHAR(16) NOT NULL,
deptid INT NOT NULL,
CONSTRAINT employee_dept_fk FOREIGN KEY(deptid) REFERENCES dept(deptid) ON UPDATE CASCADE ON DELETE CASCADE
)
INSERT INTO dept(deptName) VALUES('开发部');
INSERT INTO dept(deptName) VALUES('销售部');
INSERT INTO dept(deptName) VALUES('后勤部');
INSERT INTO employee(empName,deptid) VALUES('张三',1)
INSERT INTO employee(empName,deptid) VALUES('李四',1)
INSERT INTO employee(empName,deptid) VALUES('王五',2)
INSERT INTO employee(empName,deptid) VALUES('刘六',2)
INSERT INTO employee(empName,deptid) VALUES('唐八',3)
INSERT INTO employee(empName,deptid) VALUES('吴七',3)
分页查询
起始行从0开始
分页：当前页 每页显示多少条
分页查询当前页的数据的sql: SELECT * FROM student LIMIT (当前页-1)*每页显示多少条,每页显示多少条
第一页两条数据
SELECT * FROM employee LIMIT 0,2
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