Mybatis学习（一）

      MyBatis是支持普通SQL查询，存储过程和高级映射的优秀持久层框架。

      MyBatis消除了几乎所有的JDBC代码和参数的手工设置以及对结果集的检索封装。

      MyBatis可以使用简单的XML或注解用于配置和原始映射，将接口和Java的POJO（Plain Old Java Objects，普通的Java对象）映射成数据库中的记录.

快速入门示例：

1、引入需要的jar包

• mybatis

• MYSQL驱动包

2、数据库建表，此处以Users表为例

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('张三', 20);

INSERT INTO users(NAME, age) VALUES('李四', 25);

3、添加mybatis 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">
         </transactionManager>
         <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="123456" />
         </dataSource>
       </environment>
    </environments>
</configuration>

 4、定义表对应的实体类

package com.mybatis.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="com.mybatis.bean.User">
<select id="getUser" parameterType="int" resultType="com.mybatis.bean.User">
   select * from user where id=#{id}
</select>
</mapper>

  6、在conf.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>
    <environments default="development">
       <environment id="development">
         <transactionManager type="JDBC">
         </transactionManager>
         <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="123456" />
         </dataSource>
       </environment>
    </environments>
    <mappers>
        <mapper resource="userMapper.xml"></mapper>
    </mappers>
</configuration>

 7、编写测试代码

package com.mybatis.service;

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 com.mybatis.bean.User;

public class test {

    public static void main(String[] args) throws IOException {
        // TODO Auto-generated method stub

        String pathxml = "conf.xml";
        
        Reader reader = Resources.getResourceAsReader(pathxml);
        SqlSessionFactory sessionfactory = new SqlSessionFactoryBuilder().build(reader);
        SqlSession session = sessionfactory.openSession();
        
        String statement = "com.mybatis.bean.User.getUser";
        User user = session.selectOne(statement,1); // 1 为要查询的条件id
        
        System.out.println(user.getName());
    }

}