Mybatis的下载并搭建核心架构

Posted 2020-10-24 书安

下载网站:

　　　https://github.com/mybatis/mybatis-3/releases

1.引入web项目下引入mybatis.jar

　　引入到WebRoot/WEB-INF/lib下

2.配置 mybatis 核心配置文件(这个在mybatis源码包中)

 　　mybatis-3-mybatis-3.4.5\src\test\java\org\apache\ibatis\submitted\complex_property\Configuration.xml

 　　将Configuration.xml复制到web项目中

　　 配置核心配置文件

<configuration>
  <environments default="development">
    <environment id="development">
      <transactionManager type="JDBC">
        <property name="" value=""/>
      </transactionManager>
      <dataSource type="UNPOOLED">
        <property name="driver" value="com.mysql.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/micro_message"/>
        <property name="username" value="root"/>
        <property name="password" value="123456"/>
      </dataSource>
    </environment>
  </environments>
 
  <mappers>
    <mapper resource="com/daoan/config/sqlxml/Message.xml"/>
  </mappers>  

</configuration>

 

3.得到sqlSession对象

　　

import java.io.IOException;
import java.io.Reader;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

/**
 * 访问数据库类
 */
public class DBAccess {
    public SqlSession getSqlSession() throws IOException {
        //通过配置文件获取数据库连接信息
        Reader reader = Resources.getResourceAsReader("com/daoan/config/Configuration.xml");
        //通过配置信息构建SqlSessionFactoy
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
        //通过SqlSessionFactoy打开一个数据库会话
        SqlSession sqlSession = sqlSessionFactory.openSession();
        return sqlSession;
    }
}

 

4.使用Mybatis框架来连接连接sql以及执行sql语句

/**
 * 和Message表相关的数据库操作
 */
public class MessageDao {
    /**
     *  根据查询条件，查询消息列表
     */
    public List<Message> queryMessageList(String command,String description) {
        DBAccess dbAccess = new DBAccess();
        List <Message> messageList = new ArrayList<Message>();
        SqlSession sqlSession = null;
        try {
            sqlSession = dbAccess.getSqlSession();
            //通过sqlSession执行SQL语句
            messageList = sqlSession.selectList("Message.queryMessageList");
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            if(sqlSession !=null){
                sqlSession.close();
                sqlSession = null;
            }
        }
        return messageList;
    }
    
    public static void main(String[] args) {
        MessageDao messageDao = new MessageDao();
        messageDao.queryMessageList("", "");
    }
}

 

5.Message.xml配置文件 (取出数据库某个字段的值放在java的对象的属性里面)

<?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="Message">

  <resultMap type="com.daoan.bean.Message" id="MessageResult">
    <id column="Id" jdbcType="INTEGER" property="id"/>
    <result column="Command" jdbcType="VARCHAR" property="command"/>
    <result column="Description" jdbcType="VARCHAR" property="description"/>
    <result column="Context" jdbcType="VARCHAR" property="context"/>
  </resultMap>

  <select id="queryMessageList" resultMap="MessageResult">
    select Id,Command,Description,Context from message where 1=1
  </select>
</mapper>