Mybatis回顾

简单mybatis项目

一、导入依赖二、创建db.properties三、创建mybatis-config.xml四、编写MybatisUtil类五、编写接口类、Mapper、测试类六、结构目录
mybatis文档： https://mybatis.org/mybatis-3/zh/index.html

    
    
    
        mysql
        mysql-connector-java
        8.0.16
    
    
    
    
        org.mybatis
        mybatis
        3.5.6
    

		
    
        junit
        junit
        4.13.1
        test
    


		
	
	    
	        
	            src/main/java
	            
	                ***.xml
	            
	            false
	        
	        
	            src/main/resources
	            
	                ***.xml
	            
	            false
	        
	    
	

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=utf8&serverTimezone=Asia/Shanghai
username=root
password=x123456

添加时区serverTimezone=Asia/Shanghai，不然可能报错 serverTimezone

mappers几种写法

public class MybatisUtil {

    private static SqlSessionFactory sqlSessionFactory = null;

    static{
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static SqlSession getSqlSession(){
        //默认false, 设置为true则自动提交事务
        return sqlSessionFactory.openSession();
    }

}

（1）接口类UserMapper.java

public interface UserMapper {
    List queryAll();
    User findOneByID(int id);
}

（2）创建UserMapper.xml

    
    
        select * from user
    

namespac要求：
① namespace=“接口的全限定类名”，一个namespace绑定一个Dao接口
② sql语句的 id 必须和接口方法一致

（3）编写测试类

    @Test
    public void testQuery(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List users = mapper.queryAll();
        for (User user : users) {
            System.out.println(user);
        }
    }