Mybatis使用

• 什么是Mybatis

官网的介绍 Mybatis是 支持 自定义SQL、存储过程、高级映射的基于Java语言开发的数据库持久性框架。

 

在日常Java开发中，离不开数据库操作，Java通过JDBC来操作数据库，但JDBC操作繁琐，不利于快速开发。Mybatis把JDBC的繁琐细节都处理了，可以让我们专注业务功能的开发。

首先要明白Mybatis的两个重要概念Configuration和Mapper,Configuration用于全局配置Mybatis的参数,Mapper(映射)用于Mybatis处理SQL的方式，平时开发中都与Mapper打交道。

Configuration 主配置文件

<?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>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value=""/>
                <property name="url" value=""/>
                <property name="username" value=""/>
                <property name="password" value=""/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="maping.xml"/>
    </mappers>
</configuration>

Mapper有基于XML和注解的配置方式

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.aa.IApp">
    <select id="selectAppss" resultType="com.entity.App">
    SELECT Id,'AppId' as AppId,`Name` FROM App where Id = #{Id}
  </select>
</mapper>

注解

package com.aa;

import org.apache.ibatis.annotations.Select;

public interface IApp {
    @Select("SELECT Id,'aaaaaaaaaaaaa' as AppId,`Name` FROM App where Id = #{Id}")
    App selectApp(int id);
}

后面的代码都是基于XML的。

查询

<mapper namespace="com.aa">
    <select id="selectApp" resultType="com.entity.App">
    SELECT Id,AppId,`Name` FROM App where Id = #{Id}
  </select>
</mapper>

InputStream is=Resources.getResourceAsStream("mybatis_config.xml"); //Resources.getResourceAsStream("mybatis_config.xml");
        SqlSessionFactory sqlfactory= new SqlSessionFactoryBuilder().build(is);

        SqlSession session = sqlfactory.openSession();
        try {
            App app = session.selectOne("com.aa.selectApp", 1);
        } finally {
            session.close();
        }

查询返回集合

    <select id="selectList" resultType="com.entity.App">
    SELECT 1 as Id, 'A1' as AppId,'A2' as `Name`
    union all
    SELECT 1 as Id, 'A1' as AppId,'A2' as `Name`
    union all
    SELECT 1 as Id, 'A1' as AppId,'A2' as `Name`
  </select>

List<App> apps= session.selectList("com.aa.selectList");

修改 

    <update id="updateApp">
        update App set OwnerEmail=OwnerEmail where 1=5 and 1=#{Id};
    </update>

    <delete id="deleteApp">
        delete from App where 1=5 and 1=#{Id};
    </delete>
    <insert id="insertApp" parameterType="com.entity.App">
        insert into App(AppId,`Name`)values(#{AppId},#{Name})
    </insert>

session.update("com.aa.updateApp",-22);
            session.delete("com.aa.deleteApp",-22);

            App addApp=new App();
            addApp.setAppId("add appid");
            addApp.setName("add app name");
            session.insert("com.aa.deleteApp",addApp);

Mybatis还有一些高级特性 缓存、字段映射、动态SQL，后面继续分享。。。。