com.example.gaefirebaseeventproxy.FirebaseEventProxy.java Source code

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Here is the source code for com.example.gaefirebaseeventproxy.FirebaseEventProxy.java

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/*
 * Copyright 2016 Google Inc. All Rights Reserved.
 *
 * 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.example.gaefirebaseeventproxy;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.appengine.api.utils.SystemProperty;
import com.google.firebase.FirebaseApp;
import com.google.firebase.FirebaseOptions;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

import java.io.FileInputStream;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.util.HashMap;
import java.util.Map;
import java.util.logging.Logger;

public class FirebaseEventProxy {

    private static final Logger log = Logger.getLogger(FirebaseEventProxy.class.getName());

    public FirebaseEventProxy() {
        String firebaseLocation = "https://crackling-torch-392.firebaseio.com";
        Map<String, Object> databaseAuthVariableOverride = new HashMap<String, Object>();
        // uid and provider will have to match what you have in your firebase security rules
        databaseAuthVariableOverride.put("uid", "gae-firebase-event-proxy");
        databaseAuthVariableOverride.put("provider", "com.example");
        try {
            FirebaseOptions options = new FirebaseOptions.Builder()
                    .setServiceAccount(new FileInputStream("gae-firebase-secrets.json"))
                    .setDatabaseUrl(firebaseLocation).setDatabaseAuthVariableOverride(databaseAuthVariableOverride)
                    .build();
            FirebaseApp.initializeApp(options);
        } catch (IOException e) {
            throw new RuntimeException(
                    "Error reading firebase secrets from file: src/main/webapp/gae-firebase-secrets.json: "
                            + e.getMessage());
        }
    }

    public void start() {
        DatabaseReference firebase = FirebaseDatabase.getInstance().getReference();

        // Subscribe to value events. Depending on use case, you may want to subscribe to child events
        // through childEventListener.
        firebase.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot snapshot) {
                if (snapshot.exists()) {
                    try {
                        // Convert value to JSON using Jackson
                        String json = new ObjectMapper().writeValueAsString(snapshot.getValue(false));

                        // Replace the URL with the url of your own listener app.
                        URL dest = new URL("http://gae-firebase-listener-python.appspot.com/log");
                        HttpURLConnection connection = (HttpURLConnection) dest.openConnection();
                        connection.setRequestMethod("POST");
                        connection.setDoOutput(true);

                        // Rely on X-Appengine-Inbound-Appid to authenticate. Turning off redirects is
                        // required to enable.
                        connection.setInstanceFollowRedirects(false);

                        // Fill out header if in dev environment
                        if (SystemProperty.environment.value() != SystemProperty.Environment.Value.Production) {
                            connection.setRequestProperty("X-Appengine-Inbound-Appid", "dev-instance");
                        }

                        // Put Firebase data into http request
                        StringBuilder stringBuilder = new StringBuilder();
                        stringBuilder.append("&fbSnapshot=");
                        stringBuilder.append(URLEncoder.encode(json, "UTF-8"));
                        connection.getOutputStream().write(stringBuilder.toString().getBytes());
                        if (connection.getResponseCode() != 200) {
                            log.severe("Forwarding failed");
                        } else {
                            log.info("Sent: " + json);
                        }
                    } catch (JsonProcessingException e) {
                        log.severe("Unable to convert Firebase response to JSON: " + e.getMessage());
                    } catch (IOException e) {
                        log.severe("Error in connecting to app engine: " + e.getMessage());
                    }
                }
            }

            @Override
            public void onCancelled(DatabaseError error) {
                log.severe("Firebase connection cancelled: " + error.getMessage());
            }
        });
    }
}