mybatis
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mybatis是支持定制化sql、存储过程以及高级映射的优秀持久层框架
mybatis避免了几乎所有的jdbc代码和手动设置参数以及获取结果集
mybatis可以使用 简单的xml或者注解方式用于配置和原始映射,将接口i和java的pojo(普通的java对象)映射成数据库中的记录
mybatis入门:
mapper映射文件
<?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.atguigu.mybatis.dao.EmployeeMapper">
<!--
namespace:名称空间;指定为接口的全类名
id:唯一标识
resultType:返回值类型
#{id}:从传递过来的参数中取出id值
public Employee getEmpById(Integer id);
-->
<select id="getEmpById" resultType="com.bean.Employee">
select id,last_name lastName,email,gender from tbl_employee where id = #{id}
</select>
</mapper>
mybatis核心配置文件
<?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>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver" />
<property name="url" value="jdbc:mysql://localhost:3306/mybatis" />
<property name="username" value="root" />
<property name="password" value="123456" />
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="EmployeeMapper.xml" />
</mappers>
</configuration>
测试用例:
public class MyBatisTest {
public SqlSessionFactory getSqlSessionFactory() throws IOException {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
return new SqlSessionFactoryBuilder().build(inputStream);
}
@Test
public void test() throws IOException {
// 2、获取sqlSession实例,能直接执行已经映射的sql语句
// sql的唯一标识:statement Unique identifier matching the statement to use.
// 执行sql要用的参数:parameter A parameter object to pass to the statement.
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
SqlSession openSession = sqlSessionFactory.openSession();
try {
Employee employee = openSession.selectOne("com.mybatis.EmployeeMapper.selectEmp", 1);
System.out.println(employee);
} finally {
openSession.close();
}
}
}
接口式编程:
public interface EmployeeMapper {
public Employee getEmpById(Integer id);
}
测试:
@Test
public void test() throws IOException {
// 1、获取sqlSessionFactory对象
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
// 2、获取sqlSession对象
SqlSession openSession = sqlSessionFactory.openSession();
try {
// 3、获取接口的实现类对象
EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
Employee employee = mapper.getEmpById(1);
System.out.println(mapper.getClass());
System.out.println(employee);
} finally {
openSession.close();
}
}
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