Mybatis入门第一节

Mybatis入门第一节

MyBatis是支持普通的sql查询的，存储过程和高级映射的优秀的持久层框架，mybatis消除了几乎所有的jdbc代码和参数的手工的设置以及对结果集的检索封装，它可以使用简单的xml或者注解来配置和原始的映射，将接口和Java的pojo映射成数据库中的记录。

jdbc->dbutils(特点自动封装结果集)->MyBatis->Hibernate(基本不用写sql语句)

Hibernate可以直接跟数据库连接，MyBaties需要一个中间层（配置文件xml）来跟数据库有关系。

1：首先导入mybatis的架包mybatis-3.1.1.jar.

2：创建数据库和表

CREATE DATABASE mybatis;
USE mybatis;
CREATE TABLE users(
id INT PRIMARY KEY AUTO_INCREMENT,
NAME VARCHAR(20),
age INT


);

INSERT INTO users(NAME,age) VALUES ('tom',12);
INSERT INTO users(NAME,age) VALUES ('jack',11);

3：添加mybatis的配置文件conf.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/mybatis" />
                <property name="username" value="root" />
                <property name="password" value="root" />
            </dataSource>
        </environment>
    </environments>
</configuration>

4:定义表所对应的实体类

package bean;

public class User {

    private int id;
    private String name;
    private int age;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    
}

5：定义操作users表的sql映射文件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="bean.userMapper">
    <!-- 
        根据id查询得到一个user对象
     -->
     <select id="getUser" parameterType="int" resultType="bean.User">
         select * from users where id=#{id}
     </select>
</mapper>

6:在config.xml文件中注册userMapper.xml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>

    <properties resource="db.properties"/>
    
    
<!-- 
    development : 开发模式
    work : 工作模式
 -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <dataSource type="POOLED">
                <property name="driver" value="${driver}" />
                <property name="url" value="${url}" />
                <property name="username" value="${name}" />
                <property name="password" value="${password}" />
            </dataSource>
        </environment>
    </environments>
    
    <mappers>
        <mapper resource="bean/userMapper.xml"/>
        
    </mappers>
</configuration>

7：编写测试类

package Test;

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;

import bean.User;

public class Test {

    public static void main(String[] args) throws IOException {
        String resource = "conf.xml"; 
        //加载mybatis的配置文件（它也加载关联的映射文件）
        Reader reader = Resources.getResourceAsReader(resource); 
        //构建sqlSession的工厂
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
        //创建能执行映射文件中sql的sqlSession
        SqlSession session = sessionFactory.openSession();
        //映射sql的标识字符串
                String statement = "bean.userMapper"+".getUser";
                //执行查询返回一个唯一user对象的sql
                User user = (User)session.selectOne(statement,1);
                //User user = session.selectOne(statement, 1);
                System.out.println(user.getName());



    }

}