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I'm working on a Spring App where I need to access all the property files kept inside a folder. I tried the ReloadingCombinedConfigurationBuilder approach but the configuration is updated only once and then further file changes don't appear. Here is the code I am using:

ReloadingCombinedConfigurationBuilder combinedBuilder = new ReloadingCombinedConfigurationBuilder()
                .configure(params.fileBased().setFile(new File("configuration.xml")));

Here is my configuration.xml:

<?xml version="1.0" encoding="ISO-8859-1" ?>
<configuration>
    <properties fileName="{absolute-path}/a.properties" config-reload="true" reloadingRefreshDelay="10000"/>
    <properties fileName="{absolute-path}/b.properties" config-reload="true"/>
</configuration>

Then I add few properties Configuration programmatically. If I do not add a Configuration programmatically combinedBuilder.getReloadingController() returns null while setting trigger.

Configuration config = builder.getConfiguration();
        combinedBuilder.getConfiguration().addConfiguration(myFileBasedConfigurationBuilderconfig.getConfiguration());

And start the trigger:

PeriodicReloadingTrigger trigger = new PeriodicReloadingTrigger(
                combinedBuilder.getReloadingController(), null, 5, TimeUnit.SECONDS);
        trigger.start();

When I execute it and change the properties file the change is reflected once & then it stops providing changed values.

Suggestions are welcome.

100rabh
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3 Answers3

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I was facing the same issue until I found out that the ReloadingController needs to be explicitly reset. This is specified in the commons-configuration javadoc.

Typically one of the listeners is responsible to perform the actual reload operation. (How this is done is not in the scope of the controller object.) After this has been done, the controller's resetReloadingState() method must be called. It tells the controller that the last notification has been processed and that new checks are possible again. It is important that this method is called. Otherwise, checkForReloading() will not do any new checks or send out event notifications any more.

This is how it looks on my side:

    builder.getReloadingController().addEventListener(ReloadingEvent.ANY, new EventListener<ReloadingEvent>() {

        @Override
        public void onEvent(ReloadingEvent event) {
            // TODO reload properties
            event.getController().resetReloadingState();
        }
    });
petarov
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I was facing the exact problem, but what worked for me is instead of using a PeriodicReloadingTrigger, i was reloading the configuration when it was being accessed on a configuration request event with a Refresh Delay.

Follow is how you can configure this on your builder.

builder.addEventListener(ConfigurationBuilderEvent.CONFIGURATION_REQUEST, new EventListener() {
  @Override
  public void onEvent(Event arg0) {
    builder.getReloadingController().checkForReloading(null);
  }
});

ReloadingRefreshDelay can either set to builder params or it can be defined in the xml like you have already did.

KDV Prasad
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As of version 2.2, the ReloadingCombinedConfigurationBuilder appears to swap out its ReloadingController after every reload. (Whether it should do this is a very good question.) The original code does not work because the PeriodicReloadingTrigger is pinging a controller that is no longer attached to the builder. Prasad's answer works because he is calling builder.getReloadingController().checkForReloading(null), which always works against the current controller. In Spring you should use Spring's timing features, but pure Java you can do something like:

ScheduledExcecutorService scheduler = Executors.newSingleThreadScheduledExecutor();
scheduler.scheduleAtFixedRate(()->builder.getReloadingController().checkForReloading(null),
           delay, interval, TimeUnit.SECONDS);
user3171350
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