Java 之mybatis简单使用与配置

一、基本配置

在线文档：​​https://mybatis.org/mybatis-3/zh/index.html​​

1、下载： ​​https://github.com/mybatis/mybatis-3/releases​​

2、将mybatis-3.4.3.jar和lib下的jar包导入项目

3、创建 mybatis-config.xml，配置如下：

<?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="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/jrbac?characterEncoding=utf-8&useSSL=false"/>
                <property name="username" value="jrbac"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>

    <!-- 将我们写好的Sql映射文件，一定要注册到全局配置文件中。-->
    <mappers>
        <mapper resource="com/mapper/adminMapper.xml" />
    </mappers>

</configuration>

4、创建Sql映射文件、实体对象Admin，如：adminMapper.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.admin">
    <!--
        namespace, 名称空间。
        id, 唯一标识，同Spring的Bean标签id一样。
        resultType： 返回值类型。我这里期望他给我返回一个员工对象。
        -->

    <select id="selectAdmin" resultType="com.entity.Admin">
        select * from j_admin
    </select>

</mapper>

二、示例

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

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 com.entity.Admin;

public class Mybatis {
    public Mybatis() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream resourceAsStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory build = new SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession = build.openSession();
        
         List<Admin> list = sqlSession.selectList("selectAdmin");
         for(Admin i : list){
             System.out.println(i);
         }
         
         sqlSession.close();
         resourceAsStream.close();
    }
}

 三、mybatis工具类

package com.utils;
 
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;
 
/**
 * @author 25754
 */
public class MyBatisUntil {
    //封装会话工厂
    private static SqlSessionFactory Factory;
    /**在进行对象的跨层传递的时候，使用ThreadLocal可以避免多次传递，打破层次间的约束
     */
    private static ThreadLocal<SqlSession> local = new ThreadLocal<SqlSession>();
 
    static {
        try {
            InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
            SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
            Factory = sqlSessionFactoryBuilder.build(is);
 
        } catch (
                IOException e)
 
        {
            e.printStackTrace();
        }
    }
    //封装factory方法
    public  static SqlSessionFactory getFactory(){
        return Factory;
    }
 
    //封装sqlSession会话
    public static SqlSession getSqlSession(boolean IsAutoComiit) {
        SqlSession sqlSession = local.get();
        if (sqlSession == null) {
            sqlSession = Factory.openSession(IsAutoComiit);
            local.set(sqlSession);
        }
        return sqlSession;
    }
 
    //使用泛型封装getMapper
    public static <T extends Object> T getMapper(Class<T> c) {
        SqlSession sqlSession = getSqlSession(true);
        return sqlSession.getMapper(c);
    }
}