Doclet for filtering public classes from JavaDoc

CustomDoclet.java

package com.sightmachine.doclet;

import java.lang.reflect.Array;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.ArrayList;
import java.util.List;

import com.sun.javadoc.Doc;
import com.sun.javadoc.DocErrorReporter;
import com.sun.javadoc.ProgramElementDoc;
import com.sun.javadoc.RootDoc;
import com.sun.tools.doclets.standard.Standard;
import com.sun.tools.javadoc.Main;
import com.sun.javadoc.Doclet;
import com.sun.javadoc.LanguageVersion;

/**
  To debug, run the doclet directly on the main method. That method is not used when
  javadocs is run.

  CustomDoclet builds on top of the standard doclet interface (com.sun.javadoc.Doclet) which requires
  implementing a few methods. The actual standard doclet was copied from example code and is hacky to say the least.

  New features:
  *"@hide" which can be applied directly in the code to classes, interfaces, methods, and class members.

**/

public class CustomDoclet extends Doclet {

  public static boolean validOptions(String[][] options, DocErrorReporter reporter) {
    return Standard.validOptions(options, reporter);
  }

  public static LanguageVersion languageVersion() {
    return LanguageVersion.JAVA_1_5;
  }

  public static int optionLength(String option) {
    return Standard.optionLength(option);
  }

  public static boolean start(RootDoc root) {
    return Standard.start((RootDoc) process(root, RootDoc.class));
  }

  private static boolean exclude(Doc doc) {
    if (doc.name().contains("UnitTest")) {
      return true;
    } else if (doc.tags("@hide").length > 0) {
      return true;
    } else if (doc instanceof ProgramElementDoc) {
      if (((ProgramElementDoc) doc).containingPackage().tags("@hide").length > 0)
        return true;
    }
    // nothing above found a reason to exclude
    return false;
  }

  private static Object process(Object obj, Class expect) {
    if (obj == null)
      return null;
    Class cls = obj.getClass();
    if (cls.getName().startsWith("com.sun.")) {
      return Proxy
          .newProxyInstance(cls.getClassLoader(), cls.getInterfaces(), new ExcludeHandler(obj));
    } else if (obj instanceof Object[]) {
      Class componentType = expect.getComponentType();
      if (componentType == null) { // Without this, processing the annotation in 'FieldName.java' breaks.
        return null;
      }
      Object[] array = (Object[]) obj;
      List list = new ArrayList(array.length);
      for (int i = 0; i < array.length; i++) {
        Object entry = array[i];
        if ((entry instanceof Doc) && exclude((Doc) entry))
          continue;
        list.add(process(entry, componentType));
      }
      return list.toArray((Object[]) Array.newInstance(componentType, list.size()));
    } else {
      return obj;
    }
  }

  private static class ExcludeHandler implements InvocationHandler {

    private Object target;

    public ExcludeHandler(Object target) {
      this.target = target;
    }

    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
      if (args != null) {
        String methodName = method.getName();
        if (methodName.equals("compareTo") || methodName.equals("equals") || methodName
            .equals("overrides") || methodName.equals("subclassOf")) {
          args[0] = unwrap(args[0]);
        }
      }
      try {
        return process(method.invoke(target, args), method.getReturnType());
      } catch (InvocationTargetException e) {
        throw e.getTargetException();
      }
    }

    private Object unwrap(Object proxy) {
      if (proxy instanceof Proxy)
        return ((ExcludeHandler) Proxy.getInvocationHandler(proxy)).target;
      return proxy;
    }
  }

  public static void main(String[] args) {
    // Use this for testing and debugging the doclet. Add all arguments as java program arguments.
    String name = CustomDoclet.class.getName();
    Main.execute(name, name, args);
  }
}

Originally copied from: https://gist.github.com/benjchristensen/1410681 . Compared to the original source, I made some small modifications to fix things that were broken (e.g: some classes with annotations would break)

Hopefully, this helps anyone who needs javadocs to add this feature and are constrained for any reason.