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.

Are you looking for a list of classes that implement your annotation und use this list to initialize the array of the generated class? Is that what you want to do? — El Hoss, Apr 09 '17 at 16:23

score 0 · Answer 1 · answered Jul 09 '18 at 00:55

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.

Annotation Processor : initialize a field

1 Answers1