Copyright 2014 Netflix, Inc.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
    http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
/**
 * Copyright 2014 Netflix, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.netflix.config;

A configuration that polls a PolledConfigurationSource according to the schedule set by a scheduler. The property values in this configuration will be changed dynamically at runtime if the value changes in the configuration source. 

This configuration does not allow null as key or value and will throw NullPointerException
when trying to add or set properties with empty key or value.
Author:
awang/**
 * A configuration that polls a {@link PolledConfigurationSource} according to the schedule set by a
 * scheduler. The property values in this configuration will be changed dynamically at runtime if the
 * value changes in the configuration source.
 * <p>
 * This configuration does not allow null as key or value and will throw NullPointerException
 * when trying to add or set properties with empty key or value.
 * 
 * @author awang
 *
 */
public class DynamicConfiguration extends ConcurrentMapConfiguration {
    private AbstractPollingScheduler scheduler;
    private PolledConfigurationSource source;

    
Constant for the add property event type.
/**
     * Constant for the add property event type.
     */
    public static final int EVENT_RELOAD = 100;

    
Create an instance and start polling the configuration source.
Params:
source – PolledConfigurationSource to poll
scheduler – AbstractPollingScheduler whose AbstractPollingScheduler.schedule(Runnable) will be used to determine the polling schedule/**
     * Create an instance and start polling the configuration source.
     * 
     * @param source PolledConfigurationSource to poll
     * @param scheduler AbstractPollingScheduler whose {@link AbstractPollingScheduler#schedule(Runnable)} will be
     *                  used to determine the polling schedule
     */
    public DynamicConfiguration(PolledConfigurationSource source, AbstractPollingScheduler scheduler) {
        this();
        startPolling(source, scheduler);
    }
    
    public DynamicConfiguration() {
        super();
    }
    
    
Start polling the configuration source with the specified scheduler.
Params:
source – PolledConfigurationSource to poll
scheduler – AbstractPollingScheduler whose AbstractPollingScheduler.schedule(Runnable) will be used to determine the polling schedule/**
     * Start polling the configuration source with the specified scheduler.
     * 
     * @param source PolledConfigurationSource to poll
     * @param scheduler AbstractPollingScheduler whose {@link AbstractPollingScheduler#schedule(Runnable)} will be
     *                  used to determine the polling schedule
     */
    public synchronized void startPolling(PolledConfigurationSource source, AbstractPollingScheduler scheduler) {
        this.scheduler = scheduler;
        this.source = source;
        init(source, scheduler);

        scheduler.addPollListener(new PollListener() {
            @Override
            public void handleEvent(EventType eventType, PollResult lastResult, Throwable exception) {
                switch (eventType) {
                    case POLL_SUCCESS:
                        fireEvent(EVENT_RELOAD, null, null, false);
                        break;
                    case POLL_FAILURE:
                        fireError(EVENT_RELOAD, null, null, exception);
                        break;
                    case POLL_BEGIN:
                        fireEvent(EVENT_RELOAD, null, null, true);
                        break;
                }
            }
        });

        scheduler.startPolling(source, this);
    }
    
    
Initialize the configuration. This method is called in DynamicConfiguration(PolledConfigurationSource, AbstractPollingScheduler) and startPolling(PolledConfigurationSource, AbstractPollingScheduler) before the initial polling. The default implementation does nothing. /**
     * Initialize the configuration. This method is called in 
     * {@link #DynamicConfiguration(PolledConfigurationSource, AbstractPollingScheduler)} 
     * and {@link #startPolling(PolledConfigurationSource, AbstractPollingScheduler)}
     * before the initial polling. The default implementation does nothing.
     */
    protected void init(PolledConfigurationSource source, AbstractPollingScheduler scheduler) {
    }
    
    
Stops the scheduler
/**
     * Stops the scheduler
     */
    public synchronized void stopLoading() {
        if (scheduler != null) {
            scheduler.stop();
        }
    }
    
    public PolledConfigurationSource getSource() {
        return source;
    }    
}