MyBatis常用方法

由于下面这段代码的重复性很高，我们可以单独创建一个工具类

 		//1.加载mybatis的核心配置文件，获取SqlSessionFactory  
        String resource = "mybatis-config.xml";  
        InputStream inputStream = Resources.getResourceAsStream(resource);  
        SqlSessionFactory sqlSessionFactory =  
                new SqlSessionFactoryBuilder().build(inputStream);  
  
        //2.获取SqlSession对象，用他来执行Sql  
        SqlSession sqlSession = sqlSessionFactory.openSession();  
  

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工具类

public class MyBatisUtils {
	private static SqlSessionFactory factory;
	static {
		try {
			factory = new SqlSessionFactoryBuilder.build(new FileInputStream("mybatis-config.xml"));
		} catch(FileNotFoundException e) {
			e.printStackTrace();
		}
	}
	//自动提交
	public SqlSession openSession(boolean autoCommit) {
		return factory.openSession(autoCommit);
	}
}

简化后的代码

```java
public class TestUser {  
    @Test  
    public void testUser() throws IOException {  
        SqlSession sqlSession = MyBatisUtils.openSession(true);
        
        //3.执行Sql  
        List<User> users = sqlSession.selectList("test.selectAll");  
        System.out.println(users);  
    }  
}

selectMap方法

Map<String, User> map selectMap("selectAllUser", "id")表示以id作为key,查询到的结果作为Map

基于注解实现MyBatis

@Mapper //标记Mapper接口
@Select("执行查询语句，返回结果")
@Insert("执行插入语句")
@Update("执行更新语句")
@Delete("执行删除语句")

MyBatis

1. 添加依赖: mybatis，mariadb驱动
2. 配置数据库

    spring:
   	 datasource:
   		 url: jdbc:mariadb://localhost:3306/mybatis
   		 username: root
   		 password: root
   		 driver-class-name: org.mariadb.jdbc.Driver
   

3. 写Mapper

	@Mapper
	public interface UserInfoMapper {
		@Select("select * from userinfo") //接口方法的实现
		List<UserInfo> getUserInfoAll();
	}

selectCursor方法

Cursor<User> cursor = session.selectCursor("selectAllUser");
for(User user : cursor) {
	System.out.println(user);
	cursor.isOpen(); //是否已经开始遍历
	cursor.getCurrentIndex();//获取遍历到第几个(下标)
}
cursor.isConsumed(); //是否遍历完了

select方法

session.select("selectAllUser", context -> {
	System.out.println(context.getResultCount());
	System.out.println(context.getREsultObject());
	context.stop();
})

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