Annotation processing
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Annotation processing allows generating new Java files at build time from annotations without using reflection. It was introduced in Java 5 and lets you write processors to handle annotations. For Android, the android-apt Gradle plugin is needed to support annotation processing. A processor class extends AbstractProcessor and contains processing logic in the process() method to handle annotations and generate files. Examples generate getters automatically from fields or convert POJOs to strings.
Annotation processing
- 1. ANNOTATION PROCESSING HOW IT WORKS
- 2. ANNOTATION PROCESSING A BIT OF HISTORY ▸ Were first introduced in Java Language with the third edition of the Java Language Specification (JLS) ▸ And introduced in Java 5
- 3. ANNOTATION PROCESSING WHAT IS? ▸ Annotation processing lets you generate new Java files at build time. ▸ There is no need to use reflection. Although the generated Java files can use reflection, if you wish. ▸ Just cause performance degradation on build time.
- 4. ANNOTATION PROCESSING HOW CAN I DO ▸ Android Studio doesn’t have build in support for annotation processing. ▸ You need to use the android-apt Gradle plugin for your compile code as build time dependency without including it in the final apk.
- 5. ANNOTATION PROCESSING ▸ First: In your project's build.gradle you should use ▸ Second: Create a module Compiler ▸ Third: App’s build.gradle
- 6. ANNOTATION PROCESSING ▸ Finally: The compiler’s build.gradle ▸ plugin java instead plugin android. After all, this code going to run on the machine. Note on an Android.
- 7. ANNOTATION PROCESSING ABSTRACT PROCESSOR ▸ AbstractProcessor. Let’s have a look at the Processor API.
- 8. ANNOTATION PROCESSING THE PROCESSOR IT SELF ▸ void init (ProcessingEnvironment) ▸ All annotation processor must have a empty constructor! ▸ This is special init() which is invoked by the annotation processing tool
- 9. ANNOTATION PROCESSING THE PROCESSOR IT SELF ▸ boolean process(Set<? extends TypeElement> annotations, RoundEnvironment env) ▸ This is kind of main() method of each processor ▸ Here you write code for spanning, processing annotation and generating java files.
- 10. ANNOTATION PROCESSING LIVE CODE ▸ Let’s generate automatic getter for our fields.
- 11. ANNOTATION PROCESSING OK, SHOW ME EXEMPLES MUCH MORE…
- 12. ANNOTATION PROCESSING ABOUT ME ▸ Felipe Theodoro Gonçalves Android Developer at Elo7 @ftgoncalves ftgoncalves@gmail.com ▸ Slack Android Dev BR / Android Study Group http://brianattwell.com/android-annotation- processing-pojo-string-generator/ http://hannesdorfmann.com/annotation- processing/annotationprocessing101 Referências