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Config Listeners

Configuration change events can be listened for with Config.addListener(ConfigEventListener).

When to use it​

Use a listener to react when an entry changes, either through Config.commit() or because the file changed on the file system, for example to reload a cache.

Example​

import org.apache.juneau.config.*;
import org.apache.juneau.config.event.*;
import org.apache.juneau.config.store.*;

public class ConfigListenerExample {

    public static void main(String[] args) throws Exception {
        MemoryStore store = MemoryStore.create().build();
        store.update("MyConfig.cfg", "[MySection]\nkey1 = a\n");
        Config config = Config.create("MyConfig.cfg").store(store).build();

        // Add a listener for changes to MySection/key1
        config.addListener(events -> {
            for (ConfigEvent event : events) {
                if (event.getType() == ConfigEventType.SET_ENTRY && "MySection".equals(event.getSection()) && "key1".equals(event.getKey()))
                    System.out.println("key1 changed to " + event.getValue());
            }
        });

        config.set("MySection/key1", "b");
        config.commit();
    }
}

Options​

ConfigaddListener(ConfigEventListener)removeListener(ConfigEventListener)

The ConfigEventListener interface consists of the following method:

ConfigEventListeneronConfigChange(ConfigEvents)

The ConfigEvent class provides access to all the information about the updated entry:

ConfigEventgetType()getSection()getKey()getValue()getModifiers()getComment()getPreLines()

The listener method is triggered:

  • After Config.commit() is called.
  • When the file changes on the file system.

In both cases, the listener is triggered after the changes have been committed.

See also​