Annotation Processing Building a Java Annotation Processor Corneil du Plessis 

Agenda • What are annotation processors? • How can we use annotation processors? • How do we build an annotation processor? 

Java Annotations – A Primer • Annotations are Class metadata • Annotations can be used at runtime. • Annotations can be used at compile time. 

Annotation Processors – Why? • Generate source code or resources. • Modify existing source. • Analyse existing code to provide diagnostic feedback. 

The Problem 

Solution 

Example of Use 

Performing the check 

How – RequiresStatic annotation 

RequiresStaticSupport.checkClass 

RequiresStaticSupport.checkClass continued 

RequiresStaticSupport.checkClass continued 

RequiresStaticSupport.checkClass continued 

RequiresStaticProcessor 

Annotation Processor META-INF • File named META-INF/services/javax.annotation.processing.Processor • Content is fully qualifed names of annotation processors. 

RequestStaticProcessor Source Let’s look at the code. 

Debugging your Annotation Processors • Add Compiler option: -Xdebug - agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=7777 • Debug remote (Attach) with options: -Xdebug - agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=7777 • Set break point on process method. • Build will pause so that you can attach debugger. 

Finally • Contact: @corneil • Source Code - https://github.com/corneil/static-requirements • Resources • https://www.javacodegeeks.com/2015/09/java-annotation-proc essors.html • http://hannesdorfmann.com/annotation-processing/annotation processing101 Questions? 

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