mybatis初学总结

mybatis初学总结

2019年8月9日19:45:00

1.orm

什么是orm？

orm即对象关系映射 （object relation mapping）,即java对象和关系数据表之间的映射关系,

java实体的名字 ----- 表名

java实体的名字 ------ 字段名

orm有哪些?

SpringJDBC,beanUtils,mybaties,hibernate

myBatis和hibernate的区别?

两者底层都用了jdbc去实现功能,都有数据库连接池,

不同之处:hibernate适应于项目代码(sql)基本不变的需求下时比较方便,myBatis的应用比较灵活

myBatis主要完成的工作?

1.底层jdbc数据库连接(所以mysql-connection包还是要导)

2.运用反射技术将java实体和数据库表产生映射关系,一一对应

(另外还内含数据库连接池,所以比c3p0+beanUtils强大)

2.如何配置mybatis在eclipse?

1.导包

2.配置mybatis-config.xml文件在src下

使用mybatis的注意事项

例子:

public class Demo01 {
	public static void main(String[] args) throws IOException {
		//selectAll();
		//insertOne();
		//selectOnebyId();
		//updateOneById();
		//delectByID();
		
		SqlSession sqlSession = SqlSessionUtils.getSqlSession();
		List<Student>  studentlist = sqlSession.selectList("com.xiaoxin.bean.StudentMapper.selectAll");
		for (Student student : studentlist) {
			System.out.println(student);
		}
		
		SqlSessionUtils.releaseSqlSession(sqlSession);
		
		
		
	}

	private static void delectByID() throws IOException {
		InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
		SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
		SqlSession openSession = sqlSessionFactory.openSession();
		
		openSession.delete("com.xiaoxin.bean.StudentMapper.deleteOneByid",2);
		
		openSession.commit();
		openSession.close();
	}

	private static void updateOneById() throws IOException {
		InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
		SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
		SqlSession openSession = sqlSessionFactory.openSession();
		Student stu = new Student(2,"小芳", 22);
		openSession.update("com.xiaoxin.bean.StudentMapper.updateOneByid", stu);
		
		openSession.commit();
		openSession.close();
	}

	private static void selectOnebyId() throws IOException {
		InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
		SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
		SqlSession openSession = sqlSessionFactory.openSession();
		Student stu = openSession.selectOne("com.xiaoxin.bean.StudentMapper.selectOneById", 1);
		System.out.println(stu);
		openSession.commit();
		openSession.close();
	}

	private static void selectAll() throws IOException {
		InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
		SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
		SqlSession openSession = sqlSessionFactory.openSession();
		
		List<Student> stulist = openSession.selectList("com.xiaoxin.bean.StudentMapper.selectAll");
		for (Student student : stulist) {
			System.out.println(student);
			
		}
		
		openSession.commit();
		openSession.close();
		
	}

	private static void insertOne() throws IOException {
		//		ceshimap
				InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
				SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
				SqlSession openSession = sqlSessionFactory.openSession();
				
				Student stu = new Student("小敏", 21);
				
				
				openSession.insert("com.xiaoxin.bean.StudentMapper.saveOne", stu);
				
		//		要手动提交
				openSession.commit();
				
		//		关闭opensession对象
				openSession.close();
	}
}

xml如何配置?

mybatis-config.xml(放src下)

<?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">
<!-- 配置信息 -->
<configuration>

	<!-- 配置MyBatis的环境 -->
	<environments default="env">
		<!-- 配置一个环境 -->
		<environment id="env">
			<!-- 配置事务管理器 JDBC(有事务)、MANAGED(托管) -->
			<transactionManager type="JDBC" />
			<!-- 配置数据源 JNDI(web服务器方式定义数据源)、POOLED(自带连接池)、UNPOOLED(不带连接池) -->
			<dataSource type="POOLED">
				<!-- 连接数据库驱动 -->
				<property name="driver" value="com.mysql.jdbc.Driver" />
				<!-- 连接数据库URL -->
				<property name="url" value="jdbc:mysql://localhost:3306/mybatiesdemo1" />
				<!-- 连接数据库用户名 -->
				<property name="username" value="xiaoxin" />
				<!-- 连接数据库密码 -->
				<property name="password" value="root" />
			</dataSource>
		</environment>
		
		<!-- 配置一个环境,这里可以是别的环境,可以是别的数据库 -->
		<!-- <environment id="env">
			配置事务管理器 JDBC(有事务)、MANAGED(托管)
			<transactionManager type="POOLED" />
			配置数据源 JNDI(web服务器方式定义数据源)、POOLED(自带连接池)、UNPOOLED(不带连接池)
			<dataSource type="POOLED">
				连接数据库驱动
				<property name="driver" value="com.mysql.jdbc.Driver" />
				连接数据库URL
				<property name="url" value="jdbc:mysql://localhost:3306/aa" />
				连接数据库用户名
				<property name="username" value="root" />
				连接数据库密码
				<property name="password" value="root" />
			</dataSource>
		</environment> -->
		
		
		
		
		
		
	</environments>

	<!-- 配置XxxMapper.xml访问数据库SQL文件
	<mappers>
		<mapper resource="com/xxx/domain/ProdcutMapper.xml"/>
	</mappers> -->
	<mappers>
		<mapper resource="com/xiaoxin/bean/StudentMapper.xml"  />
	</mappers>
	
	
</configuration>

StudentMapper.Xml(放在实体类的包下)

<?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">
<!-- 定义访问数据表的SQL映射标签
	命名空间相当于这份文件的一个id号 
	namespace : 命名空间(用来区分其它的mapper文件),一般为该文件所在的全路径包名+mapper文件名
	一般在src下面的com开始
-->
<mapper namespace="com.xiaoxin.bean.StudentMapper">
	<!-- 添加
		id : 唯一的标识
		parameterType : 参数类型(用来为sql语句中的占位符赋值) 可选
	 -->
	<!-- <insert id="save" parameterType="com.xxx.mybatisqs.domain.Product">
		insert into product(product_name, product_price) values(#{name}, #{price})
	</insert> -->
	
	<insert id="saveOne" parameterType="com.xiaoxin.bean.Student" >
		insert into student(sname,age) values(#{sname},#{age})
	</insert>
	
	<select id="selectAll" resultType="com.xiaoxin.bean.Student" >
		select * from student
	</select>
											
	<select id="selectOneById" parameterType="java.lang.Integer" resultType="com.xiaoxin.bean.Student" >
		select * from student where sid = #{sid}
	</select>
	
	<update id="updateOneByid" parameterType="com.xiaoxin.bean.Student">
		update student set sname = #{sname} where sid = #{sid}
	</update>

	<delete id="deleteOneByid" parameterType="java.lang.Integer" >
		delete from student where sid = #{sid}
	
	</delete>	
	
	
	
	
	
</mapper>

3.更多参考

https://blog.youkuaiyun.com/zhongliwen1981/article/details/98586898