@Convert annotation's converter property should be Class<? extends AttributeConverter>, not Class (unsafe)

[lukasj]

Currently, the converter property for the @convert annotation is declared as follows:

Class converter() default void.class;

However, along with just generally being unsafe ("safe" use would be Class<?>), this does not properly restrict the set of classes that can be specified. My understanding is that this MUST be a class that implements javax.persistence.AttributeConverter. Therefore, the converter property should be specified like so:

Class<? extends AttributeConverter> converter() default void.class;

With this change, the developer will know at compile time if he has specified an incorrect class. Without this change, the developer will not know until he gets a runtime error, which is seriously less desirable.

[lukasj]

@glassfishrobot Commented
Reported by beamerblvd

[lukasj]

@glassfishrobot Commented
neilstockton said:
You can't do that.

Class<? extends AttributeConverter> converter() default void.class;
would not compile. "void.class" is not castable to the generic form (but is to the non-generic form, hence probably why they did it).

[lukasj]

@glassfishrobot Commented
kalgon said:
Well, you can always do something like this:

public @interface Convert {

  interface NoConversionAttributeConverter extends AttributeConverter<Object, Object> {}

  Class<? extends AttributeConverter<?, ?>>converter() default NoConversionAttributeConverter.class;
  ...
}

[lukasj]

@glassfishrobot Commented
This issue was imported from java.net JIRA JPA_SPEC-56

[lukasj]

• Issue Imported From: https://github.com/javaee/jpa-spec/issues/56
• Original Issue Raised By:@glassfishrobot
• Original Issue Assigned To: Unassigned

[gavinking]

Fixed in #487.