Java Annotations Processor：检查TypeMirror是否实现特定接口

Question

I'm working with on a Java annotations processor. My annotation, @foo is used to mark field variables that can be read to a file or from a file during runtime. However, I would like to check if the variable type implements Serializable during compile time, so that if the field is not serializable I can give a warning/error at compile time.

(I don't need to actually check if the object IS serializable, if it implements the Serializable interface I'll trust it).

I have figured out how to do the other stuff, but I can't figure out how to check if the element implements Serializable . I can use the TypeElement#getInterfaces method, but I can't figure out how to check if any of these TypeMirror 's returned are the one for Serializable .

Also, if anybody happens to know any good java.lang.model or Java Annotations tutorials, that would be helpful as well.

Edit: I have tried this...

isSerializable = false  
for(TypeMirror tm : processingEnv.getTypeUtils().directSupertypes(em.asType()))  
{  
if(isSerializable = "java.io.Serializable".equals(tm.toString()))  
{  
break;  
}  
}  

It works alright for String and Character, which directly implement Serializable , but for Integer, which inherits Serializable from the Number superclass, it does not work.

Answer 1

Instead of checking the direct supertypes, you should use Types.isAssignable to check if Serializable is one of the supertypes of the TypeMirror :

TypeMirror serializable = elementUtil.getTypeElement("java.io.Serializable").asType();
boolean isSerializable = typeUtil.isAssignable(tm, serializable);