com.google.enterprise.adaptor.secmgr.config.ConfigSingleton.java Source code

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Here is the source code for com.google.enterprise.adaptor.secmgr.config.ConfigSingleton.java

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// Copyright 2008 Google 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.google.enterprise.adaptor.secmgr.config;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Preconditions;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

import java.util.Observable;
import java.util.Observer;
import java.util.logging.Logger;

import javax.annotation.concurrent.GuardedBy;
import javax.annotation.concurrent.ThreadSafe;

/**
 * A singleton class to access configured parameters.
 */
@ThreadSafe
public class ConfigSingleton {
    private static final Logger LOGGER = Logger.getLogger(ConfigSingleton.class.getName());

    private static ConfigSingleton instance;
    @GuardedBy("class")
    private static Gson gson;
    private static final LocalObservable observable = new LocalObservable();

    private static final class LocalObservable extends Observable {
        @Override
        protected void setChanged() {
            super.setChanged();
        }
    }

    private ConfigSingleton() {
        resetInternal();
    }

    @VisibleForTesting
    public static synchronized void reset() {
        instance.resetInternal();
    }

    private synchronized void resetInternal() {
    }

    /**
     * Adds an observer that's notified of config changes.
     */
    public static void addObserver(Observer observer) {
        observable.addObserver(observer);
    }

    /**
     * Gets an observable that's notified of config changes.
     */
    public static Observable getObservable() {
        return observable;
    }

    static void setChanged() {
        observable.setChanged();
        observable.notifyObservers();
    }

    public static synchronized void setGsonRegistrations(GsonRegistrations registrations) {
        GsonBuilder builder = new GsonBuilder();
        builder.setPrettyPrinting();
        registrations.register(builder);
        gson = builder.create();
    }

    /** A type to use for passing in Gson registrations. */
    public interface GsonRegistrations {
        public void register(GsonBuilder builder);
    }

    public static synchronized Gson getGson() {
        Preconditions.checkNotNull(gson);
        return gson;
    }
}