mybatis学习笔记(二）

使用注解来进行配置

普通的CRUD

import java.util.List;
 
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;
 
import com.how2java.pojo.Category;

// 使用mapper类，一定要是一个接口  
public interface CategoryMapper {
    
    // 下面都是CRUD
    @Insert(" insert into category_ ( name ) values (#{name}) ") 
    public int add(Category category); 
        
    @Delete(" delete from category_ where id= #{id} ") 
    public void delete(int id); 
        
    @Select("select * from category_ where id= #{id} ") 
    public Category get(int id); 
      
    @Update("update category_ set name=#{name} where id=#{id} ") 
    public int update(Category category);  
        
    @Select(" select * from category_ ") 
    public List list(); 
}


/* 使用上面的SQL */
CategoryMapper mapper = session.getMapper(CategoryMapper.class);
Category c= mapper.get(8);
c.setName("修改了的Category名稱");
mapper.update(c);

一对多

public interface CategoryMapper {

    @Select(" select * from category_ ")
    @Results({ 
                // 下面一行可以省略，不影响查询
                @Result(property = "id", column = "id"),
                @Result(property = "products", javaType = List.class, column = "id",
                    many = @Many(
                    select = "com.how2java.mapper.ProductMapper.listByCategory") )
            })
// @Many 表示一对多，并且调用下面的函数来查询product
// property column 与XML配置中的含义相同
    public List list();
 
}

// 被上面来调用
public interface ProductMapper {
    
    // 返回集合，还是其他都不影响
    @Select(" select * from product_ where cid = #{cid}")
    public List listByCategory(int cid);
     
}

 

多对一

public interface ProductMapper {
    @Select(" select * from product_ ")
    @Results({ 
        @Result(property="category",column="cid",
        one=@One(select="com.how2java.mapper.CategoryMapper.get")) 
    })
    // @One 是多对一
    public List list();
}


// 被上面调用
public interface CategoryMapper {
    @Select(" select * from category_ where id = #{id}")
    public Category get(int id);
     
}

多对多同理可得