OnJava8-Examples/annotations/InterfaceExtractorProcessor.java

//: annotations/InterfaceExtractorProcessor.java
// APT-based annotation processing.
// {CompileTimeError} Not working in Java 8
// {Exec: apt -factory
// annotations.InterfaceExtractorProcessorFactory
// Multiplier.java -s ../annotations}
package annotations;
import com.sun.mirror.apt.*;
import com.sun.mirror.declaration.*;
import java.io.*;
import java.util.*;

public class InterfaceExtractorProcessor
  implements AnnotationProcessor {
  private final AnnotationProcessorEnvironment env;
  private ArrayList<MethodDeclaration> interfaceMethods =
    new ArrayList<>();
  public InterfaceExtractorProcessor(
    AnnotationProcessorEnvironment env) { this.env = env; }
  public void process() {
    for(TypeDeclaration typeDecl :
      env.getSpecifiedTypeDeclarations()) {
      ExtractInterface annot =
        typeDecl.getAnnotation(ExtractInterface.class);
      if(annot == null)
        break;
      for(MethodDeclaration m : typeDecl.getMethods())
        if(m.getModifiers().contains(Modifier.PUBLIC) &&
           !(m.getModifiers().contains(Modifier.STATIC)))
          interfaceMethods.add(m);
      if(interfaceMethods.size() > 0) {
        try {
          try (PrintWriter writer = env.getFiler().createSourceFile(annot.value())) {
            writer.println("package " +
                    typeDecl.getPackage().getQualifiedName() +";");
            writer.println("public interface " +
                    annot.value() + " {");
            for(MethodDeclaration m : interfaceMethods) {
              writer.print("  public ");
              writer.print(m.getReturnType() + " ");
              writer.print(m.getSimpleName() + " (");
              int i = 0;
              for(ParameterDeclaration parm :
                      m.getParameters()) {
                writer.print(parm.getType() + " " +
                        parm.getSimpleName());
                if(++i < m.getParameters().size())
                  writer.print(", ");
              }
              writer.println(");");
            }
            writer.println("}");
          }
        } catch(IOException ioe) {
          throw new RuntimeException(ioe);
        }
      }
    }
  }
} ///:~