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javaswingjarprogress

Java API returning progress to client

I am writing a java library ( jar ) that contains numerous API's that will be called by an external software . One of the API will be a blocking API and will be performing an operation that can be quite lengthy .

I want a way to be able to provide regular feedback ( % completion ) of the operation to the client .

NOTE Since its a library I cannot use the Java Swing mechanism of a progress bar to get and update a progress percent . Everything i search somehow leads to that .

Is there anyway to do this ?

Answer Update

Many thanks to all who posted answers . It helped me gain a grasp . I exposed the following interfaces on my jar . The client worker thread will register and listen for my progress updates . Then it will update the progress bar accordingly . 

void LongAPI(){
while{
do work ; 
fireprogress();
     }
}
public void addProgressListener(Listener listener) {
    listeners.add(listener);

}

public void removeProgressListener(Listener listener) {
    listeners.add(listener);
}

private void fireProgress(double pourcent) {
    for (Listener listener : listeners) {
        listener.setProgress(pourcent);
    }
}

The Listener is an abstract interface that all clients much implement . It has the setProgress property using which the client can update its UI as it wishes .

Solution

  • I would give it a PropertyChangeSupport object as well as addPropertyChangeListener(...) and removePropertyChangeListener(...) methods. Internally, I'd create bound properties with setters that fire the support object. This way external libraries can be notified in a standard way that the property of interest has changed. If it is a Swing based library, consider using specifically a SwingPropertyChangeSupport object so that all PropertyChangeListeners that have been added to the support object are notified on the Swing event thread.

    For example, please have a look at the answer to these questions: