myBatis入门例子

secce

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();
}
}
}