MyBatis学习笔记-HelloWorld

MyBatis配置文件

mybatis-config.xml
<properties resource>元素可以指定properties文件位置，导入里面配置的值
<typeAlias>定义了一些别名，如student，用来代替全名com..Student
<mapper>元素配置mapper.xml的位置

<?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>
<properties resource="com/endless/mybatis/helloworld/config/jdbc.properties" />
<typeAliases>
<typeAlias alias="student" type="com.endless.mybatis.helloworld.po.Student"></typeAlias>
</typeAliases>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<property name="driver" value="${driver}"/>
<property name="url" value="${url}"/>
<property name="username" value="${username}"/>
<property name="password" value="${password}"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="com/endless/mybatis/helloworld/config/student-mapper.xml" />
</mappers>
</configuration>

jdbc.properties

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/school
username=root
password=1234

mapper配置文件

student-mapper.xml
这个文件里面配置sql，namespace为对于DAO接口
<select>定义了一条select语句，id对应上面namespace定义接口里的方法，parameterType和resultType分别对应该方法的参数和返回类型

<?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.endless.mybatis.helloworld.mapper.StudentMapper">
<!-- student是在mybatis-config.xml中配置的Alias -->
<select id="getStudent" parameterType="String" resultType="student">
select * from student where id=#{studentId}
</select>
</mapper>

Mapper接口

public interface StudentMapper {
public Student getStudent(String studentId);
}
//这里Student的属性名称对和数据库的字段一致，会自动填充到Student对象中返回
public class Student {
private int id;
private String name;
private int age;
private String gender;
//省略get,set
}

测试程序

public class MyBatisTest {
public static void main(String[] args){
String resource="com/endless/mybatis/helloworld/config/mybatis-config.xml";
SqlSession sqlSession=null;
try{
//SqlSessionFactoryBuilder读取配置文件创建SqlSessionFactory对象
SqlSessionFactory sessionFactory=new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream(resource));
//sqlSessionFactory对象用来创建session,相当于JDBC的Connection对象
sqlSession=sessionFactory.openSession();
StudentMapper studentMapper=sqlSession.getMapper(StudentMapper.class);
Student student=studentMapper.getStudent("10001");
System.out.println(student);
}catch(Exception e){
e.printStackTrace();
}finally{
if(sqlSession!=null)
sqlSession.close();
}
}
}

总结