Mybatis笔记

点击进入mybatis官网
记录下简单的使用，更多使用可以进官网查看

    org.mybatis
    mybatis
    3.5.9


    mysql
    mysql-connector-java
    5.1.45
 

package com.yky.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.Date;


@Data
@NoArgsConstructor
@AllArgsConstructor
public class person {
    private int id;
    private String name;
    private String age;
    private Date creaseDate;
}

public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        try {
            InputStream inputStream = Resources.getResourceAsStream("mybatisConfig.xml");
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public static  SqlSession gerInstance(){
        return sqlSessionFactory.openSession();
    }
}

public interface PersonMapper {
    Person personQuery(@Param("person") Person person);
}

	
    
        select *
        from person where p_name = #{person.name};
    
    
    
        
        
        
        
    

动态sql
这里记录下（从官网摘抄例子）

1、if

  SELECT * FROM BLOG WHERe
  
    AND title like #{title}
  
  
    AND author_name like #{author.name}
  

2、choose、when、otherwise

  SELECT * FROM BLOG WHERe 
  
    
      AND title like #{title}
    
    
      AND author_name like #{author.name}
    
    
      AND featured = 1
    
  

1和2两种方式在后面条件都不满足时会出现这样两种sql
1、SELECT * FROM BLOG WHERe
2、SELECt * FROM BLOG WHERe 
用下面方式避免

  SELECT * FROM BLOG
  
    
         state = #{state}
    
    
        AND title like #{title}
    
    
        AND author_name like #{author.name}
    
  


3、可以用trim 自定义标签（上述实验中的sql）
 
        select *
        from person
        
        p_name = #{person.name}
        
 

  @Test
    public void query(){
        SqlSession sqlSession = MybatisUtils.gerInstance();
        PersonMapper personService = sqlSession.getMapper(PersonMapper.class);
        Person person = new Person();
        person.setName("哈哈");
        Person person1 = personService.personQuery(person);
        System.out.println(person1);
        sqlSession.close();
    }
    //结果：
    //Person(id=1, name=哈哈, age=11, creaseDate=Tue Mar 15 17:02:24 CST 2022)

用maven实验时，出现mapper文件找不到异常，maven将静态资源给过滤了，此时在maven的pom.xml文件中添加，静态资源释放就好了。

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