MyBatis入门学习（一）

所需要jar包：mybatis-3.x.x.jar 、如果需要和spring整合，还需要加入相关的包

1：看项目目录 红颜色不要关心

2：按照步骤：

1：加入jar包

2：创建数据源（configuration.xml）创建数据库（此处省略）

<?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>
    <typeAliases>
        <!--给实体类起一个别名 user -->
        <typeAlias type="com.forum.po.User" alias="User" />
    </typeAliases>
    <!--数据源配置  这块用 BD2数据库 -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="jdbc" />
            <dataSource type="POOLED">
                <property name="driver" value="com.ibm.db2.jcc.DB2Driver" />
                <property name="url" value="jdbc:db2://localhost:50000/forum" />
                <property name="username" value="DB2ADMIN" />
                <property name="password" value="admin" />
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <!--userMapper.xml装载进来  同等于把“dao”的实现装载进来 -->
        <mapper resource="myBatis/userMapper.xml" />
    </mappers>
</configuration>

3：创建实体类USER

package com.forum.po;

/**
 * 用户类
 *
 * @author db2admin
 *
 */
public class User extends Entity {
    private String name;
    private Integer age;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    public User() {
    }

}

4：创建dao接口、可以说是Mapper接口：UserMapper

package com.forum.dao;

import com.forum.po.User;

public interface UserMapper {
    public User findById(String Id);
}

5:创建dao的实现，不同于hibernarte的此处的实现为一个xml文件，也就是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">
    <!--这块等于dao接口的实现  namespace必须和接口的类路径一样-->
<mapper namespace="com.forum.dao.UserMapper">
    <!-- findById必须和接口中的方法名一样  返回一个User  就是刚才的别名  如果不弄别名要连类路径一起写 麻烦-->
    <select id="findById" parameterType="HashMap" resultType="User">
        select
        * from butone.student where id=#{id}
    </select>
</mapper>

6:测试类，MyBatisTest

package com.forum.test;

import java.io.IOException;

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.forum.dao.UserMapper;
import com.forum.po.User;

/**
 * myBatis数据库连接测试
 *
 * @author db2admin
 *
 */
public class MyBatisTest {
    /**
     * 获得MyBatis SqlSessionFactory
     * SqlSessionFactory负责创建SqlSession，一旦创建成功，就可以用SqlSession实例来执行映射语句，commit，rollback，close等方法。
     * @return
     */
    private static SqlSessionFactory getSessionFactory() {
        SqlSessionFactory sessionFactory = null;
        String resource = "configuration.xml";
        try {
            sessionFactory = new SqlSessionFactoryBuilder().build(Resources
                    .getResourceAsReader(resource));
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return sessionFactory;
    }

    public static void main(String[] args) {
        SqlSession sqlSession = getSessionFactory().openSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user = userMapper.findById("1");
        System.out.println(user.getName());

    }

}