PageHelper分页实战（SSM整合）
步骤一：引入SSM相关的jar包,包列表如下；
步骤二：创建或修改配置文件，配置文件清单如下；
applicationContext.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx" xmlns:jdbc="http://www.springframework.org/schema/jdbc"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-3.0.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd">
<context:annotation-config />
<context:component-scan base-package="com.sunfreeter.service" />
<bean id="dataSource"
class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName">
<value>com.mysql.jdbc.Driver</value>
</property>
<property name="url">
<value>jdbc:mysql://localhost:3666/pagetest?characterEncoding=UTF-8
</value>
</property>
<property name="username">
<value>root</value>
</property>
<property name="password">
<value>root!@@123</value>
</property>
</bean>
<bean id="sqlSession" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource" />
<property name="mapperLocations" value="classpath:com/sunfreeter/mapperXml/*.xml" />
<property name="typeAliasesPackage" value="com.sunfreeter.pojo" />
<property name="plugins">
<array>
<bean class="com.github.pagehelper.PageInterceptor">
<property name="properties">
<!--使用下面的方式配置参数，一行配置一个 -->
<value>
offsetAsPageNum=true
rowBoundsWithCount=true
pageSizeZero=true
reasonable=true
</value>
</property>
</bean>
</array>
</property>
</bean>
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<property name="basePackage" value="com.sunfreeter.mapper" />
</bean>
</beans>
springMVC.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx" xmlns:jdbc="http://www.springframework.org/schema/jdbc"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-3.0.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd">
<context:annotation-config/>
<context:component-scan base-package="com.sunfreeter.controller">
<context:include-filter type="annotation"
expression="org.springframework.stereotype.Controller"/>
</context:component-scan>
<mvc:annotation-driven />
<mvc:default-servlet-handler />
<bean
class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="viewClass"
value="org.springframework.web.servlet.view.JstlView" />
<property name="prefix" value="/WEB-INF/jsp/" />
<property name="suffix" value=".jsp" />
</bean>
</beans>
log4j.properties
# Global logging configuration
log4j.rootLogger=ERROR, stdout
# MyBatis logging configuration...
log4j.logger.com.sunfreeter=TRACE
# Console output...
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n
web.xml
<?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" xmlns:web="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_2_5.xsd" version="2.5">
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:applicationContext.xml</param-value>
</context-param>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<servlet>
<servlet-name>mvc-dispatcher</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:springMVC.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>mvc-dispatcher</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>
步骤三：创建业务相关的类及配置文件；
创建实体User
package com.sunfreeter.pojo;
public class User {
private int id;
private String name;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
创建Mapper文件
package com.sunfreeter.mapper;
import java.util.List;
import com.sunfreeter.pojo.User;
public interface UserMapper {
public List<User> list();
}
创建映射文件
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.sunfreeter.mapper.UserMapper">
<select id="list" resultType="com.sunfreeter.pojo.User">
select * from user
</select>
</mapper>
创建服务接口及类
package com.sunfreeter.service;
import java.util.List;
import com.sunfreeter.pojo.User;
public interface UserService {
List<User> list();
}
package com.sunfreeter.service.impl;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import com.sunfreeter.mapper.UserMapper;
import com.sunfreeter.pojo.User;
import com.sunfreeter.service.UserService;
@Service
public class UserServiceImpl implements UserService{
@Autowired
UserMapper userMapper;
public List<User> list(){
return userMapper.list();
}
}
创建控制器
package com.sunfreeter.controller;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import com.sunfreeter.pojo.User;
import com.sunfreeter.service.UserService;
@Controller
@RequestMapping("")
public class UserController {
@Autowired
UserService userService;
@RequestMapping("listUser")
public String listUser(@RequestParam(defaultValue="1",required=true,value="pageNo") Integer pageNo,ModelMap map){
Integer pageSize=4;//每页显示记录数
//分页查询
PageHelper.startPage(pageNo, pageSize);
List<User> userList = userService.list();//获取所有用户信息
PageInfo<User> pageInfo=new PageInfo<User>(userList);
map.addAttribute("pageInfo", pageInfo);
return "listUser";
}
}
步骤四:创建前台页面.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8" import="java.util.*"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<div style="width: 500px; margin: 0px auto; text-align: center">
<table align='center' border='1' cellspacing='0'>
<tr>
<td>id</td>
<td>name</td>
</tr>
<c:forEach items="${pageInfo.list}" var="c" varStatus="st">
<tr>
<td>${c.id}</td>
<td>${c.name}</td>
</tr>
</c:forEach>
</table>
<div style="text-align: center">
<p>当前 ${pageInfo.pageNum }页,总${pageInfo.pages } 页,总
${pageInfo.total } 条记录
</div>
</p>
<a href="?pageNo=${pageInfo.firstPage}">首页</a>
<c:if test="${pageInfo.hasPreviousPage }">
<a href="?pageNo=${pageInfo.pageNum-1}">上一页</a>
</c:if>
<c:if test="${pageInfo.hasNextPage }">
<a href="?pageNo=${pageInfo.pageNum+1}">下一页</a>
</c:if>
<a href="?pageNo=${pageInfo.lastPage}">最后页</a>
</div>
</div>
直到目前所有该有的文件我们都创建完了，细心的小伙伴可能已经发现了，我已经将分页一并贴出来了，那么，我们就开始看分页怎么处理，我们借助PageHelper工具包进行分页的实现，其实自己去写一个属于自己的分页也不是很难，但是在实战中我们要的是效率，所谓站在巨人的肩膀上才会看得更远嘛！
PageHelper分页的好处在于，代码比较简洁，好入手（感觉我是PageHelper的托！），可以让你把精力专注于业务上；
1、只需要引入pagehelper-5.1.0-beta2.jar和jsqlparser-1.0.jar；
2、配置文件applicationContext.xml的id="sqlSession"加上PageInterceptor插件就可以，特别是reasonable=true参数一定不能忘，它限制了超过最后一页和小于第一页传入的pageNo数，不加的话看查询日志就会发现limit 可能成为负数或者大于最大条数；
3、然后在控制器中传入pageNo参数；在进行数据库查询前加上
PageHelper.startPage(pageNo, pageSize);
在查询数据库完成后再加下面一句就可以了；
PageInfo<User> pageInfo=new PageInfo<User>(userList);
4、前端页面使用pageInfo相关参数就搞定！具体的参考我上面listUser.jsp贴出来的代码
是不是很简单？最后我们来一起看看效果
