core/java/android/os/ServiceManager.java

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * 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 android.os;

import android.util.Log;

import com.android.internal.os.BinderInternal;

import java.util.HashMap;
import java.util.Map;

/** @hide */
public final class ServiceManager {
    private static final String TAG = "ServiceManager";

    private static IServiceManager sServiceManager;
    private static HashMap<String, IBinder> sCache = new HashMap<String, IBinder>();

    private static IServiceManager getIServiceManager() {
        if (sServiceManager != null) {
            return sServiceManager;
        }

        // Find the service manager
        sServiceManager = ServiceManagerNative.asInterface(BinderInternal.getContextObject());
        return sServiceManager;
    }

    /**
     * Returns a reference to a service with the given name.
     * 
     * @param name the name of the service to get
     * @return a reference to the service, or <code>null</code> if the service doesn't exist
     */
    public static IBinder getService(String name) {
        try {
            IBinder service = sCache.get(name);
            if (service != null) {
                return service;
            } else {
                return getIServiceManager().getService(name);
            }
        } catch (RemoteException e) {
            Log.e(TAG, "error in getService", e);
        }
        return null;
    }

    /**
     * Returns a reference to a service with the given name, or throws
     * {@link NullPointerException} if none is found.
     *
     * @hide
     */
    public static IBinder getServiceOrThrow(String name) throws ServiceNotFoundException {
        final IBinder binder = getService(name);
        if (binder != null) {
            return binder;
        } else {
            throw new ServiceNotFoundException(name);
        }
    }

    /**
     * Place a new @a service called @a name into the service
     * manager.
     * 
     * @param name the name of the new service
     * @param service the service object
     */
    public static void addService(String name, IBinder service) {
        try {
            getIServiceManager().addService(name, service, false);
        } catch (RemoteException e) {
            Log.e(TAG, "error in addService", e);
        }
    }

    /**
     * Place a new @a service called @a name into the service
     * manager.
     * 
     * @param name the name of the new service
     * @param service the service object
     * @param allowIsolated set to true to allow isolated sandboxed processes
     * to access this service
     */
    public static void addService(String name, IBinder service, boolean allowIsolated) {
        try {
            getIServiceManager().addService(name, service, allowIsolated);
        } catch (RemoteException e) {
            Log.e(TAG, "error in addService", e);
        }
    }
    
    /**
     * Retrieve an existing service called @a name from the
     * service manager.  Non-blocking.
     */
    public static IBinder checkService(String name) {
        try {
            IBinder service = sCache.get(name);
            if (service != null) {
                return service;
            } else {
                return getIServiceManager().checkService(name);
            }
        } catch (RemoteException e) {
            Log.e(TAG, "error in checkService", e);
            return null;
        }
    }

    /**
     * Return a list of all currently running services.
     * @return an array of all currently running services, or <code>null</code> in
     * case of an exception
     */
    public static String[] listServices() {
        try {
            return getIServiceManager().listServices();
        } catch (RemoteException e) {
            Log.e(TAG, "error in listServices", e);
            return null;
        }
    }

    /**
     * This is only intended to be called when the process is first being brought
     * up and bound by the activity manager. There is only one thread in the process
     * at that time, so no locking is done.
     * 
     * @param cache the cache of service references
     * @hide
     */
    public static void initServiceCache(Map<String, IBinder> cache) {
        if (sCache.size() != 0) {
            throw new IllegalStateException("setServiceCache may only be called once");
        }
        sCache.putAll(cache);
    }

    /**
     * Exception thrown when no service published for given name. This might be
     * thrown early during boot before certain services have published
     * themselves.
     *
     * @hide
     */
    public static class ServiceNotFoundException extends Exception {
        public ServiceNotFoundException(String name) {
            super("No service published for: " + name);
        }
    }
}