Hamcrest custom matcher using dynamic proxy

MagicMatcher.java

public class MagicMatcher <T> implements InvocationHandler {
	
  //...

  public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
    if ("matches".equals(method.getName())) {

      for (Entry<String, Object> entry : methodMap.entrySet()) {
        String field = entry.getKey().substring(entry.getKey().indexOf("with") + 4);
        Object objectValue = extractObjectValue((T) args[0], entry.getKey());
        if (!(entry.getValue() instanceof Matcher)) {
          resultDescription.addExpectedDescription(field, objectValue);
          if (!entry.getValue().equals(objectValue)) {
            resultDescription.addMismatchDescription(field, entry.getValue());
            return new Boolean(false);
          }
        } else {
          Matcher<?> matcher = (Matcher<?>) entry.getValue();
          resultDescription.addExpectedDescription(field, objectValue);
          if (!matcher.matches(objectValue)) {
            resultDescription.addMismatchDescription(field, objectValue);
            return new Boolean(false);
          }
        }
      }

      return new Boolean(true);
    } else if ("describeTo".equals(method.getName())) {
      Description description = (Description) args[0];
      description.appendText(resultDescription.getExpectedDescription());
      return null;
    } else if ("describeMismatch".equals(method.getName())) {
      Description description = (Description) args[1];
      description.appendText(resultDescription.getMismatchDescription());
      return null;
    } else {
      if (args.length > 1) {
        throw new IllegalArgumentException("Cannot assert more than one argument at once.");
      }
      methodMap.put(method.getName(), args[0]);

      return proxy;
    }
  }
  
  //...
  
}