/*
 * Copyright 2018 - 2020 Anton Tananaev (anton@traccar.org)
 * Copyright 2018 Andrey Kunitsyn (andrey@traccar.org)
 *
 * 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 org.traccar.notificators;

import com.fasterxml.jackson.annotation.JsonProperty;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.traccar.Context;
import org.traccar.config.Keys;
import org.traccar.model.Event;
import org.traccar.model.Position;
import org.traccar.model.User;
import org.traccar.notification.NotificationMessage;
import org.traccar.notification.NotificationFormatter;

import javax.ws.rs.client.Entity;
import javax.ws.rs.client.InvocationCallback;

public class NotificatorFirebase extends Notificator {

    private static final Logger LOGGER = LoggerFactory.getLogger(NotificatorFirebase.class);

    private final String url;
    private final String key;

    public static class Notification {
        @JsonProperty("title")
        private String title;
        @JsonProperty("body")
        private String body;
        @JsonProperty("sound")
        private String sound;
    }

    public static class Message {
        @JsonProperty("registration_ids")
        private String[] tokens;
        @JsonProperty("notification")
        private Notification notification;
    }

    public NotificatorFirebase() {
        this(
                "https://fcm.googleapis.com/fcm/send",
                Context.getConfig().getString(Keys.NOTIFICATOR_FIREBASE_KEY));
    }

    protected NotificatorFirebase(String url, String key) {
        this.url = url;
        this.key = key;
    }

    @Override
    public void sendSync(long userId, Event event, Position position) {
        final User user = Context.getPermissionsManager().getUser(userId);
        if (user.getAttributes().containsKey("notificationTokens")) {

            NotificationMessage shortMessage = NotificationFormatter.formatMessage(userId, event, position,"short");

            Notification notification = new Notification();
            notification.title= shortMessage.getSubject();
            notification.body = shortMessage.getBody();
            notification.sound = "default";

            Message message = new Message();
            message.tokens = user.getString("notificationTokens").split("[, ]");
            message.notification = notification;

            Context.getClient().target(url).request()
                    .header("Authorization", "key=" + key)
                    .async().post(Entity.json(message), new InvocationCallback<Object>() {
                        @Override
                        public void completed(Object o) {
                        }

                        @Override
                        public void failed(Throwable throwable) {
                            LOGGER.warn("Firebase notification error", throwable);
                        }
                    });
        }
    }

    @Override
    public void sendAsync(long userId, Event event, Position position) {
        sendSync(userId, event, position);
    }

}

@@ -2547,16 +2547,17 @@
 on.title
+ 
 = shortM

Update src/main/java/org/traccar/notificators/NotificatorFirebase.java