MyBatis核心配置文件(sqlMapConfig.xml)、分页助手plugins演示、typeHandlers（少用）

1.typeHandlers（少用）

可实现在数据表里面是bigint类型，而你存进去的是date类型，这时就可以使用typeHanders来自定义来把date变为long存进去，也可以从数据库拿bigint变为date再输出到java的控制台

2.plugins分页助手

代码还是上一篇博客加点东西

pom.xml加入这两个：

<!--分页助手-->
        <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>

sqlMapConfig.xml配置：

<?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>

    <!--通过properties标签加载外部properties文件-->
    <properties resource="jdbc.properties"></properties>
    
    <!--自定义别名-->
    <typeAliases>
        <typeAlias type="com.itheima.domain.Sys_user" alias="user"></typeAlias>
        <!--这里还可以配多个-->
    </typeAliases>

    <!--配置分页助手插件-->
    <plugins>
        <!-- 注意：分页助手的插件 配置在通用馆mapper之前 -->
        <plugin interceptor="com.github.pagehelper.PageHelper">
            <!-- 指定方言 -->
            <property name="dialect" value="mysql"></property>
        </plugin>
    </plugins>

    <!--数据源环境-->
    <environments default="developement">
        <environment id="developement">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"></property>
                <property name="url" value="${jdbc.url}"></property>
                <property name="username" value="${jdbc.username}"></property>
                <property name="password" value="${jdbc.password}"></property>

            </dataSource>
        </environment>
    </environments>

    <!--加载映射文件-->
    <mappers>
        <mapper resource="com.itheima.mapper/UserMapper.xml"></mapper>
    </mappers>

    
</configuration>

com.itheima.mapper/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="com.itheima.mapper.UserMapper">
   
    <select id="findAllByPageHelper" resultType="user">
        SELECT * from sys_user
    </select>


</mapper>

select * from user不要分号，不然下面拼接limit会报错
对应的mapper接口（相当于dao的接口）：
com.itheima.mapper.UserMapper：

package com.itheima.mapper;

import com.itheima.domain.Sys_user;

import java.util.List;

/**
 * @author QLBF
 * @version 1.0
 * @date 2021/1/30 11:06
 */
public interface UserMapper {
    
    
    
    public List<Sys_user> findAllByPageHelper(); //根据分页查询

}

测试代码：

package com.itheima.service;

import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import com.itheima.domain.Sys_user;
import com.itheima.mapper.UserMapper;
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 org.junit.Test;

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

/**
 * @author QLBF
 * @version 1.0
 * @date 2021/1/30 11:07
 */
public class ServiceDemo {
    
    

   
    @Test
    //演示分页助手
    public void test3() throws IOException {
    
    

        InputStream resourceAsStream= Resources.getResourceAsStream("sqlMapConfig.xml");
        SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession=sqlSessionFactory.openSession(true);

        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        //设置分页相关参数，当前页+每页显示的条数,userMapper.xml的select * from user不要分号
        PageHelper.startPage(1,2);

        List<Sys_user> sys_userList  = mapper.findAllByPageHelper();
        for (Sys_user sys_user : sys_userList) {
    
    
            System.out.println(sys_user);
        }

        //获得与分页相关参数,要把上面的sys_userList放在下面
        PageInfo<Sys_user> pageInfo=new PageInfo<Sys_user>(sys_userList);
        System.out.println("当前页:"+pageInfo.getPageNum());
        System.out.println("每页显示条数:"+pageInfo.getPageSize());
        System.out.println("总条数:"+pageInfo.getTotal());
        System.out.println("总页数:"+pageInfo.getPages());
        System.out.println("上一页:"+pageInfo.getPrePage());
        System.out.println("下一页:"+pageInfo.getNextPage());
        System.out.println("是否是第一页："+pageInfo.isIsFirstPage());
        System.out.println("是否是最后一页:"+pageInfo.isIsLastPage());

        sqlSession.close();
    }
}

3.小结

本篇博客只介绍4和5,123见之前写的