Java Community | Help. Code. Learn.•10mo ago

Supplier alternative

Hey! I have some optional dependencies in my pom.xml (scope: provided). Now for each dependency I have a Hook class, which I would like to create an object of if the dependency is found. The following has bee confirmed to work:

public void register() {
  if (isEnabled("MyDependency")) {
    MyDependencyHook hook = new MyDependencyHook();
    hookManager.setMyDependencyHook(hook);
  }
}

public void register() {
  if (isEnabled("MyDependency")) {
    MyDependencyHook hook = new MyDependencyHook();
    hookManager.setMyDependencyHook(hook);
  }
}

While this works, it comes at the cost of having a bunch of code when handling multiple dependencies. So what I came up with instead is:

public void register() {
  enable("MyDependency", MyDependencyHook::new, hookManager::setMyDependencyHook);
}

private <T> void enable(String name, Supplier<T> supplier, Consumer<T> consumer) {
  if (!isEnabled(name)) return;
  
  T instance = supplier.get();
  consumer.accept(instance);
}

public void register() {
  enable("MyDependency", MyDependencyHook::new, hookManager::setMyDependencyHook);
}

private <T> void enable(String name, Supplier<T> supplier, Consumer<T> consumer) {
  if (!isEnabled(name)) return;
  
  T instance = supplier.get();
  consumer.accept(instance);
}

This cleans up my code base quite a bit, however, this will cause a java.lang.NoClassDefFoundError, which I believe is caused by the static reference of the hook? Can someone help me figure out an alternative? Any help is greatly appreciated^^

6 Replies

JavaBot•10mo ago

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AzeOP•10mo ago

It seems the function gets executed immediately, and the get method only returns the result. Is there an alternative that only executes the function on method call?

Kyo-chan•10mo ago

Use reflection

JavaBot•10mo ago

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AzeOP•10mo ago

private <T> void enable(String name, Class<T> clazz, Consumer<T> consumer) {
  if (isEnabled(name)) return;

  try {
    T instance = clazz.getDeclaredConstructor().newInstance();
    consumer.accept(instance);
  } catch (NoSuchMethodException | InstantiationException | IllegalAccessException | InvocationTargetException e) {
    e.printStackTrace();
  }
}

private <T> void enable(String name, Class<T> clazz, Consumer<T> consumer) {
  if (isEnabled(name)) return;

  try {
    T instance = clazz.getDeclaredConstructor().newInstance();
    consumer.accept(instance);
  } catch (NoSuchMethodException | InstantiationException | IllegalAccessException | InvocationTargetException e) {
    e.printStackTrace();
  }
}

same issue

JavaBot•10mo ago

💤 Post marked as dormant

This post has been inactive for over 300 minutes, thus, it has been archived. If your question was not answered yet, feel free to re-open this post or create a new one. In case your post is not getting any attention, you can try to use /help ping. Warning: abusing this will result in moderative actions taken against you.

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Supplier alternative