Daggerate your code - Write your own annotation processor
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The document discusses annotation processing in Java, including libraries that are useful for annotation processing like Google AutoService and Square JavaPoet. It provides an overview of the basic structure of an annotation processor class and explains how to access elements from the source code being processed. It also covers how to generate new source code files using JavaPoet and write them out using the Filer. Debugging annotation processors is discussed.
![AnnotationProcessor
for (AnnotationMirror annotationMirror : ((DeclaredType)module).asElement().getAnnotationMirrors()) {
for (Map.Entry<? extends ExecutableElement, ? extends AnnotationValue> entry :
annotationMirror.getElementValues().entrySet()) {
// use the entry with AnnotationValueVisitor
}
}
Get annotations from TypeMirror:
final String[] annotationParam = new String[1];
final AnnotationValueVisitor valueVisitor = new AnnotationValueVisitor();
valueVisitor.setFunction(new Function<TypeMirror, Void>() {
@Nullable @Override public Void apply(@Nullable TypeMirror param) {
TypeMirror moduleClass = param; //assembles modules list
return null;
}
});
annotationParam[0] = entry.getKey().getSimpleName().toString();
entry.getValue().accept(valueVisitor, null);
@Annotation(param = { Sample.class })
Class<?>[] param()
Sample.class](https://image.slidesharecdn.com/daggerate-170317080438/85/Daggerate-your-code-Write-your-own-annotation-processor-24-320.jpg)
![Debugging
● Annotation processing cannot
be debugged directly
● Compile project with gradle
in debug mode
● Attach to the compile process
from IDE
● [OPTIONAL] configure scripts
to launch debug from IDE
Detailed tutorial here](https://image.slidesharecdn.com/daggerate-170317080438/85/Daggerate-your-code-Write-your-own-annotation-processor-31-320.jpg)
Daggerate your code - Write your own annotation processor
- 1. Daggerate your code ANNOTATION PROCESSING Bartosz Kosarzycki @bkosarzycki
- 2. ● Annotations in Java ● Libraries useful in annotation processing ● Basic annotation processor ● Round environment ● Idea ● How to write your annotation processor tutorial ● Debug annotation processing Agenda
- 3. Annotations in Java: - since Java 1.5 - store meta-information #pragma in c / c# attributes - JSR-269 - since 1.6 Pluggable Annotation Processing API for apt tool, built-into javac - custom annotations
- 4. Annotations in Java: - Annotation @Retention how long annotations are kept SOURCE, CLASS, RUNTIME
- 5. Annotations in Java: SOURCE discarded by the compiler CLASS kept int the class file, not loaded by the JVM at runtime RUNTIME loaded by the JVM at runtime
- 6. Libraries ● Google AutoService link register implementations of well-known types using META-INF metadata ● Square JavaPoet link generate Java source code ● Google Compile-Testing link test javac compilation process
- 7. Basic annotation processor @AutoService(Processor.class) public class YourProcessor extends AbstractProcessor { @Override public boolean process(Set<? extends TypeElement> set, RoundEnvironment roundEnvironment) { return false; } }
- 8. @AutoService(Processor.class) public class YourProcessor extends AbstractProcessor { @Override public Set<String> getSupportedAnnotationTypes() { return Collections.singleton( Injection.class.getCanonicalName() ); } @Override public SourceVersion getSupportedSourceVersion() { return SourceVersion.latest(); } @Override public synchronized void init(ProcessingEnvironment processingEnv) { } } Implement these methods as well Basic annotation processor
- 9. Basic annotation processor @AutoService(Processor.class) public class YourProcessor extends AbstractProcessor { @Override public boolean process(Set<? extends TypeElement> set, RoundEnvironment roundEnvironment) { return false; } }
- 11. Processing rounds javac apt rounds until there is no change in sources source source
- 12. set the annotation types requested to be processed roundEnvironment environment information about the current and prior round return: whether or not the set of annotations are claimed by this processor @Override public boolean process(Set<? extends TypeElement> set, RoundEnvironment roundEnvironment) { return false; } *** always return false
- 14. RoboJuice + Dagger 2 RoboJuice DYNAMIC final RoboInjector injector = RoboGuice.getInjector(context); annotation injector.injectMembers(this); or foo = injector.getInstance(Foo.class); Dagger 2 Compile time No runtime overhead of scanning the classpath
- 15. Idea Modules can be imported dynamically Modules expose Dagger 2 injectable objects Module 1 Module 2 App Developer imports modules Injector constains MembersInjector & Providers maps Injector.get() & Injector.inject() methods work dynamically REUSABLE ANDROID SDK ENVIRONMENT Android developer
- 16. dependencies { compile 'com.you.app:module.one:6.6.6' } @Injection(modules = { ModuleOne.class }) public class MainApplication extends Application { } Foo foo = Injector.getInstance(Foo.class);
- 17. How to write an annotation processor?
- 18. @Override public Set<String> getSupportedAnnotationTypes() { return Collections.singleton( Injection.class.getCanonicalName() ); } How-to Set annotations supported by your processor: Set supported java-source version: @Override public SourceVersion getSupportedSourceVersion() { return SourceVersion.latest(); // SourceVersion.RELEASE_8; }
- 19. @Override public synchronized void init(ProcessingEnvironment processingEnv) { filer = processingEnv.getFiler(); } How-to Get “Filer” to write source code: Files are written to: build/generated/source/apt/debug build/generated/source/apt/release
- 20. Hint Class Object TypeMirror - Use description of types instead of types - Classes are NOT available yet - they are STILL COMPILED Class<?> clazz = Class.forName("your.app.package.YourType"); ClassNotFoundException
- 21. @Example public class Foo { private int a; private Other other; public Foo () { } public void setA ( int newA ) { } } Type descriptions TypeElement VariableElement ExecutableElement ExecutableElement TypeElement
- 22. Analyse source Gather information Write new source files Modify current source files Use gathered information
- 23. AnnotationProcessor for (Element typeElement : roundEnvironment.getElementsAnnotatedWith(Injection.class)) { String name = typeElement.getSimpleName().toString(); } Get all elements with a specific annotation: typeElement.getEnclosedElements(); typeElement.getEnclosingElement(); Moving up & down the type hiararchy:
- 24. AnnotationProcessor for (AnnotationMirror annotationMirror : ((DeclaredType)module).asElement().getAnnotationMirrors()) { for (Map.Entry<? extends ExecutableElement, ? extends AnnotationValue> entry : annotationMirror.getElementValues().entrySet()) { // use the entry with AnnotationValueVisitor } } Get annotations from TypeMirror: final String[] annotationParam = new String[1]; final AnnotationValueVisitor valueVisitor = new AnnotationValueVisitor(); valueVisitor.setFunction(new Function<TypeMirror, Void>() { @Nullable @Override public Void apply(@Nullable TypeMirror param) { TypeMirror moduleClass = param; //assembles modules list return null; } }); annotationParam[0] = entry.getKey().getSimpleName().toString(); entry.getValue().accept(valueVisitor, null); @Annotation(param = { Sample.class }) Class<?>[] param() Sample.class
- 26. Square’s JavaPoet Thank you @JakeWharton ;) ● works with TypeMirrors out of the box ● adds imports automatically ● removes duplicate imports ● supports static imports ● code & control flow for / if etc. ● built-in support for Filer
- 27. JavaPoet MethodSpec.Builder constructorMethod = MethodSpec.constructorBuilder().addModifiers(Modifier.PUBLIC) .addCode("this(" + "$1T" + ".builder().build()); n", typeMirror); Create methods using JavaPoet: TypeSpec typeSpec = TypeSpec.classBuilder(outputClassName) .addModifiers(Modifier.PUBLIC) .superclass(...) .addJavadoc("annotation processor ...") .addField(componentElem, "innerField", Modifier.PRIVATE, Modifier.FINAL) .addMethod(constructorMethod.build()) .build(); Create types using JavaPoet: * imports are added automatically here
- 28. JavaPoet ClassName.get("your.package.name”, "DaggerInjector") Create custom unreachable types (ClassName) : * imports are added automatically as well
- 29. Filer JavaFile.builder("your.package.name", typeSpec).build().writeTo(filer); Write source code using JavaPoet & Filer: filer.createSourceFile("public class A() {}", null); Write source code Filer:
- 30. Debugging
- 31. Debugging ● Annotation processing cannot be debugged directly ● Compile project with gradle in debug mode ● Attach to the compile process from IDE ● [OPTIONAL] configure scripts to launch debug from IDE Detailed tutorial here
- 32. Links - Angelika Langer, Annotation Processing link - Hannes Dorfmann, Annotation Processing 101 link link - JavaDocs: Element, TypeElement, ExecutableElement