mybaits 使用pagehelper实现分页

一 pageHelper功能介绍

1.1 概述

1.mybaits可以使用第3方的插件来对功能进行扩展，分页助手pagehelper是将分页的负责操作进行封装，使用简单的方式即可获得分页的相关数据。

1.2  开发步骤

1.导入通用pageHelper的坐标

2.在mybaits的核心配置文件中配置pagehelper的插件

3.测试分页数据

二   操作案例

2.1 工程结构

2.2 配置pom依赖

    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.13</version>
      <scope>test</scope>
    </dependency>
    <!--mywql dueong  -->
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.32</version>
    </dependency>
    <!--mybaits -->
    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.4.5</version>
    </dependency>
    <!-- log4j-->
    <dependency>
      <groupId>log4j</groupId>
      <artifactId>log4j</artifactId>
      <version>1.2.17</version>
    </dependency>
    <!-- 分页插件-->
    <dependency>
      <groupId>com.github.pagehelper</groupId>
      <artifactId>pagehelper</artifactId>
      <version>3.7.5</version>
    </dependency>
    <dependency>
      <groupId>com.github.jsqlparser</groupId>
      <artifactId>jsqlparser</artifactId>
      <version>0.9.1</version>
    </dependency>

2.3 配置javabean

package com.ljf.mybaits.plugs.pagehelper.bean;

/**
 * @ClassName: User
 * @Description: TODO
 * @Author: liujianfu
 * @Date: 2021/01/23 20:45:36 
 * @Version: V1.0
 **/
public class User
{
    private int id;
    private String userName;
    private String password;


    public int getId() {
        return id;
    }

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

    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;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", userName='" + userName + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

2.4 配置dao层

package com.ljf.mybaits.plugs.pagehelper.dao;

import com.ljf.mybaits.plugs.pagehelper.bean.User;


import java.io.IOException;
import java.util.List;

public interface UserMapper {
    List<User> findAll() throws IOException;
    List<User> findByIds(List<Integer> dataList) throws IOException;
}

2.5 配置service层

1.service的接口层

package com.ljf.mybaits.plugs.pagehelper.service;

import com.ljf.mybaits.plugs.pagehelper.bean.User;


import java.io.IOException;
import java.util.List;

public interface UserService {
    List<User> findAll() throws IOException;
}

2.service的实现层

package com.ljf.mybaits.plugs.pagehelper.service.impl;

import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import com.ljf.mybaits.plugs.pagehelper.bean.User;
import com.ljf.mybaits.plugs.pagehelper.dao.UserMapper;
import com.ljf.mybaits.plugs.pagehelper.service.UserService;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

/**
 * @ClassName: UserServiceImpl
 * @Description: TODO
 * @Author: liujianfu
 * @Date: 2021/01/30 22:00:02 
 * @Version: V1.0
 **/
public class UserServiceImpl implements UserService {

    @Override
    public List<User> findAll() throws IOException {
        //加载核心配置文件
        InputStream resourcesAsStream= Resources.getResourceAsStream("mybaitsConfig.xml");
        //获得sqlsession 工厂对象
        SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(resourcesAsStream);
        //获得sqlsession对象
        SqlSession sqlSession=sqlSessionFactory.openSession();
        //执行sql
        UserMapper orgMapper=sqlSession.getMapper(UserMapper.class);
        //设置分页参数
        PageHelper.startPage(1,1);
        List<User> userList=orgMapper.findAll();
        //获得与分页相关参数
        PageInfo<User> pageInfo=new PageInfo<User>(userList);
        System.out.println("当前页："+pageInfo.getPageNum());
        System.out.println("煤业显示条数："+pageInfo.getPageSize());
        System.out.println("总条数："+pageInfo.getTotal());
        System.out.println("上一页："+pageInfo.getPrePage());
        System.out.println("下一页："+pageInfo.getNextPage());
        System.out.println("是否第一个:："+pageInfo.isIsFirstPage());
        System.out.println("下一页："+pageInfo.isIsLastPage());
        //mybaits 执行更新操作，提交事务
        sqlSession.commit();
        //关闭释放资源
        sqlSession.close();
        return userList;
    }
}

2.6 resource下的配置文件

1.userMapper.xml

<?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="yonghuMapper">  -->
<mapper namespace="com.ljf.mybaits.plugs.pagehelper.dao.UserMapper">
     <!-- 查询， 在mybaitsconfig.xml文件中给起了别名 -->
    <select id="findAll" resultType="yonghu">
        select id,user_name userName,password from tb_user
    </select>



</mapper>

2.mybaits-jdbc.properties 配置文件

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/nongda
jdbc.username=root
jdbc.password=

3.mybaitsconfig.xml配置文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<properties resource="mybaits-jdbc.properties"></properties>
    <!-- 起别名-->
    <typeAliases>
      <typeAlias type="com.ljf.mybaits.plugs.pagehelper.bean.User" alias="yonghu"></typeAlias>
    </typeAliases>
    <!-- 注册类型注册器
    <typeHandlers>
        <typeHandler handler="com.mybaits.demo.handler.DataTypeTransfer"></typeHandler>
    </typeHandlers>
    -->
    <!--配置分页插件 -->
    <plugins>
        <plugin interceptor="com.github.pagehelper.PageHelper">
            <property name="dialect" value="mysql"/>
        </plugin>
    </plugins>
<!-- 数据源环境 -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>
 <!-- xxxmapper.xml都要在mybaits.config.xml文件中注册-->
    <mappers>
        <mapper resource="com/mybaits/mapper/UserMapper.xml"></mapper>
    </mappers>

</configuration>

2.7 调用

package com.ljf.mybaits.plugs.pagehelper;

import com.ljf.mybaits.plugs.pagehelper.bean.User;
import com.ljf.mybaits.plugs.pagehelper.service.UserService;
import com.ljf.mybaits.plugs.pagehelper.service.impl.UserServiceImpl;

import java.io.IOException;
import java.util.List;

/**
 * Hello world!
 *
 */
public class App 
{
    public static void main( String[] args ) throws IOException {
        UserService os=new UserServiceImpl();
        List<User> orgList=os.findAll();
        System.out.println("orglist:"+orgList);
        for(User u:orgList){
            System.out.println("u:"+u.getUserName());
        }
        System.out.println("....");
        System.out.println( "Hello World!" );
    }
}

结果：