java - 枚举上的 JPQL LIKE 表达式

Question

JPQL 可以对枚举执行 LIKE 表达式吗？

如果我有一个带有枚举字段 bar 的实体 Foo，我可以在 MySQL 中执行以下操作(bar 存储为 MySQL 枚举)...

SELECT * FROM Foo WHERE `bar` LIKE '%SUFFIX'

但是，JPQL中对应的查询...

SELECT f FROM Foo f WHERE f.bar LIKE '%SUFFIX'

...提示...

Parameter value [%SUFFIX] was not matching type [com.example.Foo$EnumType] 

Answer 1

我认为这是不可能的，LIKE 的左侧部分应该是一个string_expression(在标准 JPA 中)。来自规范:

4.6.9 Like Expressions

The syntax for the use of the comparison operator [NOT] LIKE in a conditional expression is as follows:

string_expression [NOT] LIKE pattern_value [ESCAPE escape_character]

The string_expression must have a string value. The pattern_value is a string literal or a string-valued input parameter in which an underscore (_) stands for any single character, a percent (%) character stands for any sequence of characters (including the empty sequence), and all other characters stand for themselves. The optional escape_character is a single-character string literal or a character-valued input parameter (i.e., char or Character) and is used to escape the special meaning of the underscore and percent characters in pattern_value.

enum_expression 不是string_expression。

下面的方法可以工作(使用enum literals):

SELECT f 
  FROM Foo f 
 WHERE f.bar = com.acme.Bar.SOME_CONSTANT 
    OR f.bar = com.acme.Bar.SOME_OTHER_CONSTANT

另一种选择是将 bar 字段实际存储为 String(并在 getter/setter 中对枚举进行一些转换)。

引用

• JPA 1.0 规范
  • 第 4.6.9 节“喜欢的表达方式”
  • 第 4.14 节“BNF”