MyBatis入门示例

说明：

1，本文采用的Mybatis框架版本为： mybatis-3.0.4.jar

2， 以持久化一个简单的User bean为例

User实体类的代码如下：

package bean;

public class User {
    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(String name, Integer age) {
       super();
       this.name = name;
       this.age = age;
    }

    public User() {
       super();
    }  //必须要有这个无参构造方法，不然根据UserMapper.xml中的配置，在查询数据库时，将不能反射构造出User实例
}

 

User实体的映射器取名为UserMapper(接口)，其代码如下

package Mapper;
import bean.User;

public interface UserMapper {
    public void insertUser(User user);
    public User getUser(String name);
}

注意，该接口类似于Hibernate中的DAO层接口，唯一不同的是，MyBatis中，只声明该接口就可以，不需要去实现.

UserMapper映射器对应的配置文件如下(相当于Hibernate中的User.hbm.xml,当然这里面不是属性映射字段，而是直接是映射器中各种方法对应的sql语句)：

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
    PUBLIC "-////DTD Mapper 3.0//EN"
    "http:///dtd/mybatis-3-mapper.dtd">
<mapper namespace="Mapper.UserMapper">
<!-- 这里namespace必须是UserMapper接口的路径，不然要运行的时候要报错 “is not known to the MapperRegistry”-->
    <insert id="insertUser" parameterType="User">
       insert into vincent_user(name,age) values(#{name},#{age})
       <!-- 这里sql结尾不能加分号，否则报“ORA-00911”的错误 -->
    </insert>

    <!-- 这里的id必须和UserMapper接口中的接口方法名相同，不然运行的时候也要报错 -->
    <select id="getUser" resultType="User" parameterType="java.lang.String">
        select * from vincent_user where name=#{name}
    </select>
</mapper>

MyBatis的配置文件这里取名为mybatis-config.xml其配置代码如下(相当与Hibernate的hibernate.cfg.xml):

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
    PUBLIC "-////DTD Config 3.0//EN"
    "http:///dtd/mybatis-3-config.dtd">

<configuration>
    <settings>
        <!-- changes from the defaults for testing -->
        <setting name="cacheEnabled" value="false" />
        <setting name="useGeneratedKeys" value="true" />
        <setting name="defaultExecutorType" value="REUSE" />
    </settings>
    <typeAliases>
       <typeAlias alias="User" type="bean.User"/>
    </typeAliases>
    <environments default="development">
       <environment id="development">
           <transactionManager type="jdbc"/>
           <dataSource type="POOLED">
              <property name="driver" value="oracle.jdbc.driver.OracleDriver"/>
              <property name="url" value="jdbc:oracle:thin:@192.168.56.201:1521:system"/>
              <property name="username" value="vincent"/>
              <property name="password" value="1234"/>
           </dataSource>
       </environment>
    </environments>
    <mappers>
        <mapper resource="resource/UserMapper.xml" />
    </mappers>
</configuration>

加载配置文件得到sqlSessionFactory的工具类

package Util;

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

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

public class MyBatisUtil  {
    private  final static SqlSessionFactory sqlSessionFactory;
    static {
       String resource = "resource/mybatis-config.xml";
       Reader reader = null;
       try {
           reader = Resources.getResourceAsReader(resource);
       } catch (IOException e) {
           System.out.println(e.getMessage());

       }
       sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
    }

    public static SqlSessionFactory getSqlSessionFactory() {
       return sqlSessionFactory;
    }
}

测试代码如下：

package TestMapper;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.junit.Test;

public class TestMapper {
    static SqlSessionFactory sqlSessionFactory = null;
    static {
       sqlSessionFactory = MyBatisUtil.getSqlSessionFactory();
    }

    @Test
    public void testAdd() {
       SqlSession sqlSession = sqlSessionFactory.openSession();
       try {
           UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
           User user = new User("tom",new Integer(5));
           userMapper.insertUser(user);
           sqlSession.commit();//这里一定要提交，不然数据进不去数据库中
       } finally {
           sqlSession.close();
       }
    }

    @Test
    public void getUser() {
       SqlSession sqlSession = sqlSessionFactory.openSession();
       try {
           UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
           User user = userMapper.getUser("jun");
           System.out.println("name: "+user.getName()+"|age: "+user.getAge());
       } finally {
           sqlSession.close();
       }
    }

}