My presentation about Annotations Processor Tool on Droidcon Spain 2015.

1. Annotation Processing
Tools
101

2. Txus Ballesteros
@txusballesteros
Rubén Serrano
@akelael

3. Agenda
1. Annotation Processing Tool
2. Discusión
3. Caso práctico

4. ¿Qué es eso de APT?

5. public @interface DummyAnnotiation {}
Anotación

6. Retención
• Constructor
• Atributo
• Variable
• Método
• Parámetro
• Etc.
• Source
• Class
• Runtime
Objetivo

7. Anotación
@Retention(CLASS) @Target(FIELD)
public @interface InjectView {
int value();
}

8. Runtime
Class tiene la magia:
• getAnnotation(Class<T> annotationType)
• getAnnotations()
• getDeclaredAnnotations()
• isAnnotationPresent(Class<T> annotationType)

9. Mirror API
http://docs.oracle.com/javase/1.5.0/docs/guide/apt/mirror/overview-summary.html

10. Discusión

11. Caso Práctico

12. Android Transformer
https://github.com/txusballesteros/android-transformer

13. Creando Anotaciones
@Retention(RetentionPolicy.SOURCE)
@Target(ElementType.TYPE)
public @interface Mappable {
Class<?> with();
}

14. Creando Anotaciones
@Retention(RetentionPolicy.SOURCE)
@Target(ElementType.TYPE)
public @interface Mappable {
Class<?> with();
}

15. Configurando las Anotaciones
@Retention(RetentionPolicy.SOURCE)
@Target(ElementType.TYPE)
public @interface Mappable {
Class<?> with();
}

16. Configurando las Anotaciones
@Retention(RetentionPolicy.SOURCE)
@Target(ElementType.TYPE)
public @interface Mappable {
Class<?> with();
}

17. @SupportedSourceVersion(SourceVersion.RELEASE_7)
@SupportedAnnotationTypes({
"com.mobandme.android.transformer.compiler.Mapping",
"com.mobandme.android.transformer.compiler.Mappable",
"com.mobandme.android.transformer.compiler.Parse"
})
public class AnnotationsProcessor extends AbstractProcessor {
RoundEnvironment roundEnvironment;
Map<String, MapperInfo> mappersList;
@Override
public boolean process(Set<? extends TypeElement> annotations,
RoundEnvironment roundEnv) {
return true;
}
Creando el Procesador

18. @SupportedSourceVersion(SourceVersion.RELEASE_7)
@SupportedAnnotationTypes({
"com.mobandme.android.transformer.compiler.Mapping",
"com.mobandme.android.transformer.compiler.Mappable",
"com.mobandme.android.transformer.compiler.Parse"
})
public class AnnotationsProcessor extends AbstractProcessor {
RoundEnvironment roundEnvironment;
Map<String, MapperInfo> mappersList;
@Override
public boolean process(Set<? extends TypeElement> annotations,
RoundEnvironment roundEnv) {
return true;
}
Creando el Procesador

19. @SupportedSourceVersion(SourceVersion.RELEASE_7)
@SupportedAnnotationTypes({
"com.mobandme.android.transformer.compiler.Mapping",
"com.mobandme.android.transformer.compiler.Mappable",
"com.mobandme.android.transformer.compiler.Parse"
})
public class AnnotationsProcessor extends AbstractProcessor {
RoundEnvironment roundEnvironment;
Map<String, MapperInfo> mappersList;
@Override
public boolean process(Set<? extends TypeElement> annotations,
RoundEnvironment roundEnv) {
return true;
}
Configurando el Procesador

20. Implementando el Procesador
@SupportedSourceVersion(SourceVersion.RELEASE_7)
@SupportedAnnotationTypes({
"com.mobandme.android.transformer.compiler.Mapping",
"com.mobandme.android.transformer.compiler.Mappable",
"com.mobandme.android.transformer.compiler.Parse"
})
public class AnnotationsProcessor extends AbstractProcessor {
RoundEnvironment roundEnvironment;
Map<String, MapperInfo> mappersList;
@Override
public boolean process(Set<? extends TypeElement> annotations,
RoundEnvironment roundEnv) {
return true;
}

21. Implementando el Procesador
private void processMappedAnnotationElements() {
Set<? extends Element> elements =
roundEnvironment.getElementsAnnotatedWith(Mapped.class);
for (Element mappedElement : elements) {
if (mappedElement.getKind() == ElementKind.FIELD) {
Mapped mappedAnnotation =
mappedElement.getAnnotation(Mapped.class);
String toFieldName = mappedAnnotation.toField();
}
}
}

22. Implementando el Procesador
private void processMappedAnnotationElements() {
Set<? extends Element> elements =
roundEnvironment.getElementsAnnotatedWith(Mapped.class);
for (Element mappedElement : elements) {
if (mappedElement.getKind() == ElementKind.FIELD) {
Mapped mappedAnnotation =
mappedElement.getAnnotation(Mapped.class);
String toFieldName = mappedAnnotation.toField();
}
}
}

23. Implementando el Procesador
private void processMappedAnnotationElements() {
Set<? extends Element> elements =
roundEnvironment.getElementsAnnotatedWith(Mapped.class);
for (Element mappedElement : elements) {
if (mappedElement.getKind() == ElementKind.FIELD) {
Mapped mappedAnnotation =
mappedElement.getAnnotation(Mapped.class);
String toFieldName = mappedAnnotation.toField();
}
}
}

24. Implementando el Procesador
private void processMappedAnnotationElements() {
Set<? extends Element> elements =
roundEnvironment.getElementsAnnotatedWith(Mapped.class);
for (Element mappedElement : elements) {
if (mappedElement.getKind() == ElementKind.FIELD) {
Mapped mappedAnnotation =
mappedElement.getAnnotation(Mapped.class);
String toFieldName = mappedAnnotation.toField();
}
}
}

25. Generando el Código
JavaFileObject file =
processingEnv.getFiler().createSourceFile(name);
BufferedWriter buffer =
new BufferedWriter(file.openWriter());
//…
buffer.close();

26. Configurando el Entorno
com.mobandme.android.transformer.compiler.internal.AnnotationsProcessor

27. Configuración de Gradle para el Compilador
buildscript {
repositories {
maven {
url "https://oss.sonatype.org/content/repositories/snapshots/"
}
jcenter()
}
dependencies {
classpath 'com.jimdo.gradle:gradle-apt-plugin:0.5-SNAPSHOT'
}
}
apply plugin: 'java'
apply plugin: 'apt'

28. El resultado final

29. ¿Preguntas?