Annotations across modules

[Alex Buckley]

On 11/12/2015 5:50 AM, Stephen Colebourne wrote:
> My understanding of annotations today is that annotations are not
> required at runtime. ie. if an annotation is placed into a class at
> compile time but the .class file for the annotation is not available
> on the runtime classpath. then there is no error.
>
> Does this change in any way with modules?

No.

> My specific case is wrt @ConstructorProperties which is in java.beans.
> In 9, a user may run my software without the java.beans module. Can I
> safely assume that if the annotation is available on the compile
> module path but not the runtime module path, everything will be OK
> (ie. no error)?

Yes, subject to assumptions that your software doesn't crash if it can't 
get a Class object for the java.beans.ConstructorProperties annotation type.

The fact that the java.beans package is part of the huge java.desktop 
module (due to unfortunate use of AWT types in Beans signatures) is the 
reason why JMX recently introduced its own annotation type for 
constructor properties (javax.management.ConstructorParameters). With an 
eye on behavioral compatibility, some JMX spec work was needed to 
account for when the @java.beans.ConstructorProperties annotation is 
present but the java.beans.ConstructorProperties annotation type is not 
available. See the discussion around JDK-7199353 at 
http://mail.openjdk.java.net/pipermail/jmx-dev/2015-October/thread.html.

Alex