Mybatis入门实例理论回顾

附上sql:

CREATE TABLE `student`  (
  `sid` char(10) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `sname` char(20) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `sc` double(5, 2) NULL DEFAULT NULL,
  `sm` double(5, 2) NULL DEFAULT NULL,
  `se` double(5, 2) NULL DEFAULT NULL,
  `st` double(5, 2) NULL DEFAULT NULL,
  PRIMARY KEY (`sid`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Compact;

SET FOREIGN_KEY_CHECKS = 1;
//然后自己再去插数据进行调试

@AllArgsConstructor
@NoArgsConstructor
@Data
public class Student {
	private String sid;
	private String sname;
	private double sc ;
	private double sm ;
	private double se ;
	private double st ;
}

StudengtMapper.xml

	
 		select * from student where sid = #{sid} 
 		
 	
	

conf.xml

StudentMapper接口：

package org.koma.entity;
public interface StudentMapper {
	
	//方法名和id值一致，输入参数类型与parameterType一致，方法返回值与resultType一致
	Student queryStudentById(String sid);
}

package org.koma.entity;
import java.io.IOException;
import java.io.Reader;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

public class TestMyBatis {
	public static void main(String[] args) throws IOException {
		
		//加载MyBatis配置文件（为了访问数据库）
		Reader reader = Resources.getResourceAsReader("conf.xml") ;
		SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader) ;//SqlSessionFactory工厂
		//session - connection。session就能进行数据库操作
		SqlSession session = sessionFactory.openSession() ;
		
		//第一种方法，基础方式CRUD 使用statment定位namespace和id
		String statement = "org.koma.entity.StudentMapper." + " queryStudentById" ;//namespace + id
		Student student = session.selectOne(statement,"2017160402") ;//selectOne(statement，arg)查询一个,selectList(statement，arg)查询全部
		System.out.println("通过直接statement+select_id的方式映射mapper.xml :n"+student.toString()+"n");
		
		
		//第二种方法(动态代理方式建接口类映射)：通过StudenMapper接口映射不同数据库mapper.xml，StudenMapper接口类名跟mapper.xml的namespace一致
		StudentMapper studentmapper = session.getMapper(StudentMapper.class);
		Student student2 = studentmapper.queryStudentById("2017160402");//接口的xx方法
		//如果是增删改操作，需要执行session.commit()提交事务 (conf指定的原因）
		System.out.println("通过通过StudenMapper接口映射不同数据库mapper.xml :n"+student2.toString());
		
		
		session.close(); 
	}
}

Mybatis其他相关：
Mybatis中输入参数说明及其他配置
Mybatis输出参数实例
Mybatis调用存储过程实例
Mybatis动态SQL及关联查询实例