myBatis入门例子

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 "-//mybatis.org//DTD Mapper 3.0//EN" 
    "http://mybatis.org/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 "-//mybatis.org//DTD Config 3.0//EN" 
    "http://mybatis.org/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(); 
       } 
    } 
 
}

评论

2 楼 18289753290 2014-05-24  

我加了dtd也没有提示，求指导

1 楼 heyangfeng 2011-05-18  

大哥，问下，加入了dtd文件，不能提示，是啥原因？