mybatis-milu

# 查询创建器

与Spring-Data-JPA的查询创建器一致，如果你用过Spring-Data-JPA，那么对此应当熟悉。

使用注解com.yuehuanghun.mybatis.milu.annotation.NamingQuery

部分场景可结合注解com.yuehuanghun.mybatis.milu.annotation.StatementOptions进行使用

# 示例
@Mapper
public interface StudentMapper extends BaseMapper<Student, Long> {

	@NamingQuery
	public List<Student> findByName(String name);
	@NamingQuery
	public int countByName(String name);
	@NamingQuery
	public List<Student> findByClasssName(String className);	
	@NamingQuery
	public List<Student> findTop5ByAddTimeAfter(Date addTimeBegin);
	@NamingQuery
	public List<Student> findByClasssNameOrderByClasssIdDescAddTimeAsc(String className);
}

在mapper中，使用@NamingQuery标识一个接口为查询创建器，否则会认为映射的的是由xml配置的statement
与Spring-Data-JPA一样，查询属性可以为关联实体的属性

@Mapper
public interface ClassMapper extends BaseMapper<Classs, Long> {

	@NamingQuery
	public List<Classs> findByTeacherListName(String teacherName);
	
	@NamingQuery
	public List<Classs> findByStudentListName(String studentName);
	
	@NamingQuery
	public List<Classs> findByStudentListNameInAndStudentListAgeGreaterThan(String[] studentNames, int age);

}

结合@StatementOptions使用，可以设置查询的列、设置查询表达式，设置查询表达则替换方法名为表达式

@Mapper
public interface StudentMapper extends BaseMapper<Classs, Long> {

	@NamingQuery
  @StatementOptions(selects = "age")
	public Long findAgeById(Long id); // 只查一个属性时，可以以属性的类型为查询值返回类型
	
	@NamingQuery
  @StatementOptions(asExpression = "findByClasssNameOrderByClasssIdDescAddTimeAsc") // 可以避免方法名过长，但会使方法名表达不够准确
	public List<Student> findByClasssName(String className);

}

# 条件关键字

关键字 例子 JPQL 片段
And findByLastnameAndFirstname … where x.lastname = ?1 and x.firstname = ?2
Or findByLastnameOrFirstname … where x.lastname = ?1 or x.firstname = ?2
Between findByStartDateBetween … where x.startDate between 1? and ?2
LessThan findByAgeLessThan … where x.age < ?1
GreaterThan findByAgeGreaterThan … where x.age > ?1
After findByStartDateAfter … where x.startDate > ?1
Before findByStartDateBefore … where x.startDate < ?1
IsNull findByAgeIsNull … where x.age is null
IsNotNull,NotNull findByAge(Is)NotNull … where x.age not null
Like findByFirstnameLike … where x.firstname like ?1
NotLike findByFirstnameNotLike … where x.firstname not like ?1
StartingWith findByFirstnameStartingWith … where x.firstname like ?1(parameter bound with appended %)
EndingWith findByFirstnameEndingWith … where x.firstname like ?1(parameter bound with prepended %)
Containing findByFirstnameContaining … where x.firstname like ?1(parameter bound wrapped in %)
OrderBy findByAgeOrderByLastnameDesc … where x.age = ?1 order by x.lastname desc
Not findByLastnameNot … where x.lastname <> ?1
In findByAgeIn(Collection ages) … where x.age in ?1
NotIn findByAgeNotIn(Collection age) … where x.age not in ?1
True findByActiveTrue() … where x.active = true
False findByActiveFalse() … where x.active = false

# 操作关键字

关键字 例子 JPQL 片段
find/read/get/query/stream findByLastname select ... where x.lastname = ?1
count countByLastname select count(*) from ... where x.lastname = ?1
Distinct findDistinctByLastname select distinct ... where x.lastname = ?1
delete/remove deleteByLastname delete from ... where x.lastname = ?1

# 行限制关键字(示例目标数据库为Mysql)

关键字 例子 JPQL 片段
Top findTop5ByLastname select ... where x.lastname = ?1 limit 5
First findFirstByLastname select ... where x.lastname = ?1 limit 1

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