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1. MyBatis 简介
1. 传统 JDBC 编程
2. ORM 模型
Object Relational Model，对象映射模型：数据库的表和 POJO （Plain Ordinary Java Object） 的映射关系模型。
3. Hibernate
全表映射；不能组装 SQL；对多表关联和复杂 SQL 查询支持较差；性能较差。
4. MyBatis
半自动映射框架：手工匹配提供 POJO、SQL 和映射关系。
5. 什么时候用 MyBatis
mybais-helloworld
mybatis-config.xml
<?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/test"/> <property name="username" value="root"/> <property name="password" value="root"/> </dataSource> </environment> </environments> <mappers> <mapper resource="com\sunyard\dao\xml\UserMapper.xml"/> </mappers></configuration>
User.java
package com.sunyard.model;import java.util.Date;/** * Created by gaoeb on 2017/4/24. */public class User { private int id; private String username; private String password; private int credits; private String lastIp; private Date lastVisit; private Date createTime; private Date updateTime; private int status; // getter and setter}
UserMapper.java
package com.sunyard.dao;import com.sunyard.model.User;/** * Created by gaoeb on 2017/4/24. */public interface UserMapper { User getUserById(int id);}
UserMapper.xml
<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.sunyard.dao.UserMapper"> <select id="getUserById" parameterType="java.lang.Integer" resultType="com.sunyard.model.User"> SELECT id AS id, username AS username, password AS password, credits AS credits, last_ip AS lastIp, last_visit AS lastVisit, create_time AS createTime, update_time AS updateTime, status AS status FROM t_user WHERE id = #{id} </select></mapper>
MyBatisUtil.java
package com.sunyard.util;import org.apache.ibatis.io.Resources;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;import java.io.IOException;/** * Created by gaoeb on 2017/4/24. */public class MyBatisUtil { private static SqlSessionFactory sqlSessionFactory = null; public static SqlSessionFactory getSessionFactory() { if (sqlSessionFactory == null) { try { sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml")); return sqlSessionFactory; } catch (IOException e) { e.printStackTrace(); } } return sqlSessionFactory; }}
Main.java
import com.sunyard.dao.UserMapper;import com.sunyard.model.User;import com.sunyard.util.MyBatisUtil;import org.apache.ibatis.session.SqlSession;public class Main { public static void main(String[] args) { System.out.println("Hello World!"); SqlSession session = MyBatisUtil.getSessionFactory().openSession(); UserMapper userMapper = session.getMapper(UserMapper.class); User user = userMapper.getUserById(1); System.out.println(user.toString()); session.close(); }}
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1. MyBatis 简介
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