com.ocpsoft.pretty.faces.config.reload.PrettyConfigReloader.java Source code

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Here is the source code for com.ocpsoft.pretty.faces.config.reload.PrettyConfigReloader.java

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/*
 * Copyright 2010 Lincoln Baxter, III
 * 
 * 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.ocpsoft.pretty.faces.config.reload;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

import javax.servlet.ServletContext;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.ocpsoft.common.services.ServiceLoader;

import com.ocpsoft.pretty.faces.config.PrettyConfigurator;
import com.ocpsoft.pretty.faces.spi.DevelopmentModeDetector;

/**
 * This class reloads the PrettyFaces configuration if PrettyFaces runs in development mode.
 * 
 * @author Christian Kaltepoth
 */
public class PrettyConfigReloader {

    private final Log log = LogFactory.getLog(this.getClass());

    /**
     * The configuration is reloaded after this amount of time
     */
    private final static long CONFIG_RELOAD_DELAY = 2000l;

    /**
     * Keeps track of the last time the configuration was updated
     */
    private long lastUpdate = 0;

    /**
     * The development mode will be lazily detected
     */
    private Boolean developmentMode = null;

    public void reloadIfNecessary(ServletContext servletContext) {
        // the development mode detection is started when the first request is received
        if (developmentMode == null) {

            developmentMode = isDevelopmentModeActive(servletContext);

            if (log.isDebugEnabled()) {
                if (developmentMode) {
                    log.debug("PrettyFaces development mode detected! Configuration reloading will be enabled.");
                } else {
                    log.debug("No development mode detected. Configuration reloading gets disabled.");
                }
            }

        }

        // reloading is only done if in development mode
        if (developmentMode != null && developmentMode.booleanValue()) {

            // the point in time the configuration will be reloaded
            long nextUpdate = lastUpdate + CONFIG_RELOAD_DELAY;

            if (System.currentTimeMillis() > nextUpdate) {

                if (log.isDebugEnabled()) {
                    log.debug("Reloading PrettyFaces configuration...");
                }

                /*
                 * first update the 'lastUpdate' so that concurrent requests won't
                 * also do an update of the configuration.
                 */
                lastUpdate = System.currentTimeMillis();

                // run the configuration procedure again
                PrettyConfigurator configurator = new PrettyConfigurator(servletContext);
                configurator.configure();

            }
        }

    }

    /**
     * Detects the PrettyFaces development mode using the {@link DevelopmentModeDetector} SPI.
     */
    private boolean isDevelopmentModeActive(ServletContext servletContext) {

        // create the ServiceLoader for the SPI
        ServiceLoader<DevelopmentModeDetector> serviceLoader = ServiceLoader.load(DevelopmentModeDetector.class);

        // we need a list to be able to sort it
        List<DevelopmentModeDetector> detectors = new ArrayList<DevelopmentModeDetector>();
        for (DevelopmentModeDetector detector : serviceLoader) {
            detectors.add(detector);
        }

        // sort them by priority
        Collections.sort(detectors, new Comparator<DevelopmentModeDetector>() {
            public int compare(DevelopmentModeDetector left, DevelopmentModeDetector right) {
                return left.getPriority() - right.getPriority();
            }
        });

        // process the detectors until one returns a result != null
        for (DevelopmentModeDetector detector : detectors) {

            Boolean result = detector.isDevelopmentMode(servletContext);

            if (log.isDebugEnabled()) {
                log.debug("Detector " + detector.getClass().getSimpleName() + " returned: " + result);
            }

            if (result != null) {
                return result.booleanValue();
            }

        }

        // default value
        return false;

    }

}