三种开发方式
MyBatis三种开发方式分别为:
1. dao对象 + xml
2. mapper代理对象 + xml
3. mapper代理对象 + 注解
其中,第三种代理对象 + 注解最为常见。
dao对象 + xml
dao层对象手动创建SqlSession对象,手动实现方法,并和xml文件中的标签进行sql配对。
mybatis-config.xml
<mappers> <mapper resource="mapper/StudentMapper.xml"></mapper> </mappers>
StudentSerivce.java
public class StudentService { private StudentDao dao = new StudentDao(); public void insert(Student student) { dao.insert(student); } }
StudentDao.java
public class StudentDao { private SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder(); private SqlSessionFactory factory = builder.build(Thread.currentThread().getContextClassLoader().getResourceAsStream("mybatis-config.xml")); private SqlSession sqlSession = factory.openSession(true); public void insert(Student student) { sqlSession.insert("insert", student); } }
StudentMapper.xml
<?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="dao.StudentDao"> <insert id="insert"> insert into student (`name`, `age`, `sex`) values (#{name}, #{age}, #{sex}) </insert> </mapper>
mapper代理对象 + xml
使用动态代理机制,dao层接口化,底层自动创建代理对象代替dao对象创建SqlSession,并且自动与xml文件进行sql配对。
注意,这里代理对象管理的SqlSession匹配方法,规定了方法的id必须为方法名。
mybatis-config.xml
<mappers> <mapper resource="mapper/StudentMapper.xml"></mapper> </mappers>
StudentSerivce.java
public class StudentService { private StudentDao dao = SqlSessionUtil.getMapper(StudentDao.class); public void insert(Student student) { dao.insert(student); } }
StudentDao.java
public interface StudentDao { void insert(Student student); }
StudentMapper.xml
<?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="dao.StudentDao"> <insert id="insert"> insert into student (`name`, `age`, `sex`) values (#{name}, #{age}, #{sex}) </insert> </mapper>
mapper代理对象 + 注解
使用动态代理机制,dao层接口化,底层自动创建代理对象代替dao对象创建SqlSession,并且自动从注解中提取sql。
注意,使用注解后,就可以省去对应的一个xml文件。
mybatis-config.xml
<mappers> <mapper class="dao.StudentDao"></mapper> </mappers>
StudentSerivce.java
public class StudentService { private StudentDao dao = SqlSessionUtil.getMapper(StudentDao.class); public void insert(Student student) { dao.insert(student); } }
StudentDao.java
public interface StudentDao { @Insert("insert into student (`name`, `age`, `sex`) values (#{name}, #{age}, #{sex})") void insert(Student student); }