MyBatis学习笔记

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

1<?xml version="1.0" encoding="UTF-8" ?>
2<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
3<configuration>
4	<properties resource="com/endless/mybatis/helloworld/config/jdbc.properties" />
5	<typeAliases>
6		<typeAlias alias="student" type="com.endless.mybatis.helloworld.po.Student"></typeAlias>
7	</typeAliases> 
8	<environments default="development">
9		<environment id="development">
10			<transactionManager type="JDBC" />
11			<dataSource type="POOLED">
12				<property name="driver" value="${driver}"/>
13				<property name="url" value="${url}"/>
14				<property name="username" value="${username}"/>
15				<property name="password" value="${password}"/>
16			</dataSource>
17		</environment>
18	</environments>
19	<mappers>
20		<mapper resource="com/endless/mybatis/helloworld/config/student-mapper.xml" />
21	</mappers>
22</configuration>

jdbc.properties

1driver=com.mysql.jdbc.Driver
2url=jdbc:mysql://localhost:3306/school
3username=root
4password=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

1<?xml version="1.0" encoding="UTF-8" ?>
2<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
3
4<mapper namespace="com.endless.mybatis.helloworld.mapper.StudentMapper">
5	<!-- student是在mybatis-config.xml中配置的Alias -->
6	<select id="getStudent" parameterType="String" resultType="student">
7		select * from student where id=#{studentId}
8	</select>
9</mapper>

Mapper接口

1public interface StudentMapper {
2	public Student getStudent(String studentId);
3}
4//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
5public class Student {
6	private int id;
7	private String name;
8	private int age;
9	private String gender;
10 	//省略get,set
11}

测试程序

1public class MyBatisTest {
2	public static void main(String[] args){
3		String resource="com/endless/mybatis/helloworld/config/mybatis-config.xml";
4		SqlSession sqlSession=null;		
5		try{
6			//SqlSessionFactoryBuilder读取配置文件创建SqlSessionFactory对象
7			SqlSessionFactory sessionFactory=new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream(resource));
8			//sqlSessionFactory对象用来创建session,相当于JDBC的Connection对象
9			sqlSession=sessionFactory.openSession();
10			StudentMapper studentMapper=sqlSession.getMapper(StudentMapper.class);
11			Student student=studentMapper.getStudent("10001");
12			System.out.println(student);
13		}catch(Exception e){
14			e.printStackTrace();			
15		}finally{		
16			if(sqlSession!=null)
17				sqlSession.close();
18		}
19	}
20}

总结