Annotation Processor : initialize a field

Question

I am writing an annotation processor in android which generates a java file. I am using JavaPoet library for that.

The purpose of generated file: It should have a list of names of the classes with a particular annotation that my processor supports and provide a public method to get that list.

Now, I've generated the file:

 private final List<String> names;

 GeneratedFile(ArrayList<String> names) {
    this.names = names;
 }

 public List<String> getNames() {
   return names;
}

Now, the problem is: How do I initialize the names field from the processor? The Javapoet api provides an initializer for the field but that only takes a string. In my processor, I've the list of classes that have my supported annotation. I want to populate this field with that list.

Answer 1

As you already know, JavaPoet offers only a string to specify field initialization. To accomplish your task you have to (I will show you some code that is not specific to your problem, but it can be a good example to show you how to do it):

• Get from your annotation processor the list of classes with your annotation (the code is copied from a my library ):

   @Override public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) { model = new PrefsModel(); parseBindType(roundEnv); // Put all @BindSharedPreferences elements in beanElements for (Element item : roundEnv.getElementsAnnotatedWith(BindSharedPreferences.class)) { AssertKripton.assertTrueOrInvalidKindForAnnotationException(item.getKind() == ElementKind.CLASS, item, BindSharedPreferences.class); // store type name somewhere } return true; } 

• Use this set of TypeName to generate the initial value for you field:

   ... Builder sp = FieldSpec.builder(ArrayTypeName.of(String.class), "COLUMNS", Modifier.STATIC, Modifier.PRIVATE, Modifier.FINAL); String s = ""; StringBuilder buffer = new StringBuilder(); for (SQLProperty property : entity.getCollection()) { buffer.append(s + "COLUMN_" + columnNameToUpperCaseConverter.convert(property.getName())); s = ", "; } classBuilder.addField(sp.addJavadoc("Columns array\\n").initializer("{" + buffer.toString() + "}").build()); ... 

You will find my library on github . In particular, you have to read the class com.abubusoft.kripton.processor.sqlite.BindTableGenerator .

Hope this information can be still useful.