An initial commit for Firebase Event Proxy

appengine/firebase-event-proxy/README.md

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+# App Engine Firebase Event Proxy
+
+An example app that illustrates how to create a Java App Engine Standard Environment
+app that proxies Firebase events to another App Engine app.
+
+# Java Firebase Event Proxy
+Illustrates how to authenticate and subscribe to Firebase from Java App Engine.
+
+# Python App Engine Listener
+Illustrates how to authenticate messages received from the proxy app.
+
+## Setup
+
+### Java Firebase Event Proxy
+Firebase Secret
+Put your Firebase secret in the file:
+gae-firebase-event-proxy/src/main/webapp/firebase-secret.properties
+```
+firebaseSecret=<Your Firebase secret>
+```
+
+* Billing must be enabled from Cloud console.
+* Manual scaling should turned on and configured to 1 instance in appengine-web.xml
+
+## Running locally
+### Java Firebase Event Proxy
+```
+cd gae-firebase-event-proxy
+mvn appengine:devserver
+```
+
+### Python App Engine Listener
+```
+cd gae-firebase-listener-python
+dev_appserver .
+```
+
+## Deploying
+
+### Java Firebase Event Proxy
+```
+cd gae-firebase-event-proxy
+mvn appengine:upload
+```
+
+### Python App Engine Listener
+```
+appcfg.py -A <your app id> -V v1 update gae-firebase-listener-python
+```

appengine/firebase-event-proxy/gae-firebase-event-proxy/pom.xml

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+<!--
+ Copyright 2015 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.
+-->
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+
+    <modelVersion>4.0.0</modelVersion>
+    <packaging>war</packaging>
+    <version>1.0-SNAPSHOT</version>
+
+    <groupId>com.example.GaeFirebaseEventProxy</groupId>
+    <artifactId>GaeFirebaseEventProxy</artifactId>
+
+    <properties>
+        <app.id>gae-firebase-event-proxy</app.id>
+        <app.version>1</app.version>
+        <appengine.version>1.9.36</appengine.version>
+        <gcloud.plugin.version>2.0.9.74.v20150814</gcloud.plugin.version>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <maven.compiler.showDeprecation>true</maven.compiler.showDeprecation>
+    </properties>
+
+    <prerequisites>
+        <maven>3.1.0</maven>
+    </prerequisites>
+
+    <dependencies>
+        <!-- Compile/runtime dependencies -->
+        <dependency>
+            <groupId>com.google.appengine</groupId>
+            <artifactId>appengine-api-1.0-sdk</artifactId>
+            <version>${appengine.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>javax.servlet</groupId>
+            <artifactId>servlet-api</artifactId>
+            <version>2.5</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>jstl</groupId>
+            <artifactId>jstl</artifactId>
+            <version>1.2</version>
+        </dependency>
+        <dependency>
+          <groupId>com.firebase</groupId>
+          <artifactId>firebase-client-jvm</artifactId>
+          <version>[1.0.8,)</version>
+        </dependency>
+        <dependency>
+          <groupId>com.fasterxml.jackson.core</groupId>
+          <artifactId>jackson-core</artifactId>
+          <version>2.7.3</version>
+        </dependency>
+        <dependency>
+            <groupId>com.firebase</groupId>
+            <artifactId>firebase-token-generator</artifactId>
+            <version>2.0.0</version>
+        </dependency>
+
+        <!-- Test Dependencies -->
+        <dependency>
+            <groupId>com.google.appengine</groupId>
+            <artifactId>appengine-testing</artifactId>
+            <version>${appengine.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.google.appengine</groupId>
+            <artifactId>appengine-api-stubs</artifactId>
+            <version>${appengine.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <!-- for hot reload of the web application-->
+        <outputDirectory>${project.build.directory}/${project.build.finalName}/WEB-INF/classes</outputDirectory>
+        <plugins>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>versions-maven-plugin</artifactId>
+                <version>2.1</version>
+                <executions>
+                    <execution>
+                        <phase>compile</phase>
+                        <goals>
+                            <goal>display-dependency-updates</goal>
+                            <goal>display-plugin-updates</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <version>3.1</version>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>1.7</source>
+                    <target>1.7</target>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-war-plugin</artifactId>
+                <version>2.4</version>
+                <configuration>
+                    <archiveClasses>true</archiveClasses>
+                    <webResources>
+                        <!-- in order to interpolate version from pom into appengine-web.xml -->
+                        <resource>
+                            <directory>${basedir}/src/main/webapp/WEB-INF</directory>
+                            <filtering>true</filtering>
+                            <targetPath>WEB-INF</targetPath>
+                        </resource>
+                    </webResources>
+                </configuration>
+            </plugin>
+
+            <plugin>
+                <groupId>com.google.appengine</groupId>
+                <artifactId>appengine-maven-plugin</artifactId>
+                <version>${appengine.version}</version>
+                <configuration>
+                    <enableJarClasses>false</enableJarClasses>
+                    <version>${app.version}</version>
+                    <!-- Comment in the below snippet to bind to all IPs instead of just localhost -->
+                    <!-- address>0.0.0.0</address>
+                    <port>8080</port -->
+                    <!-- Comment in the below snippet to enable local debugging with a remote debugger
+                         like those included with Eclipse or IntelliJ -->
+                    <!-- jvmFlags>
+                      <jvmFlag>-agentlib:jdwp=transport=dt_socket,address=8000,server=y,suspend=n</jvmFlag>
+                    </jvmFlags -->
+                </configuration>
+            </plugin>
+            <plugin>
+              <groupId>com.google.appengine</groupId>
+              <artifactId>gcloud-maven-plugin</artifactId>
+              <version>${gcloud.plugin.version}</version>
+              <configuration>
+                <set_default>true</set_default>
+              </configuration>
+            </plugin>
+        </plugins>
+    </build>
+</project>

appengine/firebase-event-proxy/gae-firebase-event-proxy/src/main/java/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 java.io.FileInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.HttpURLConnection;
+import java.net.URL;
+import java.net.URLEncoder;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Properties;
+import java.util.logging.Logger;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.firebase.client.AuthData;
+import com.firebase.client.DataSnapshot;
+import com.firebase.client.Firebase;
+import com.firebase.client.FirebaseError;
+import com.firebase.client.ValueEventListener;
+import com.firebase.security.token.TokenGenerator;
+import com.google.appengine.api.utils.SystemProperty;
+
+public class FirebaseEventProxy {
+
+  private static final Logger log = Logger.getLogger(FirebaseEventProxy.class.getName());
+
+  private String firebaseAuthToken;
+
+  public FirebaseEventProxy() {
+    // Store Firebase authentication token as an instance variable.
+    this.firebaseAuthToken = this.getFirebaseAuthToken(this.getFirebaseSecret());
+  }
+
+  public void start() {
+    String FIREBASE_LOCATION = "https://gae-fb-proxy.firebaseio.com/";
+    Firebase firebase = new Firebase(FIREBASE_LOCATION);
+
+    // Authenticate with Firebase
+    firebase.authWithCustomToken(this.firebaseAuthToken, new Firebase.AuthResultHandler() {
+      @Override
+      public void onAuthenticationError(FirebaseError error) {
+        log.severe("Firebase login error: " + error.getMessage());
+      }
+
+      @Override
+      public void onAuthenticated(AuthData auth) {
+        log.info("Firebase login successful");
+      }
+    });
+
+    // 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());
+
+            // 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(FirebaseError error) {
+        log.severe("Firebase connection cancelled: " + error.getMessage());
+      }
+    });
+  }
+
+  private String getFirebaseSecret() {
+    Properties props = new Properties();
+    try {
+      // Read from src/main/webapp/firebase-secrets.properties
+      InputStream inputStream = new FileInputStream("firebase-secret.properties");
+      props.load(inputStream);
+      return props.getProperty("firebaseSecret");
+    } catch (java.net.MalformedURLException e) {
+      throw new RuntimeException(
+          "Error reading firebase secrets from file: src/main/webapp/firebase-sercrets.properties: "
+              + e.getMessage());
+    } catch (IOException e) {
+      throw new RuntimeException(
+          "Error reading firebase secrets from file: src/main/webapp/firebase-sercrets.properties: "
+              + e.getMessage());
+    }
+  }
+
+  private String getFirebaseAuthToken(String firebaseSecret) {
+    Map<String, Object> authPayload = new HashMap<String, Object>();
+    // uid and provider will have to match what you have in your firebase security rules
+    authPayload.put("uid", "gae-firebase-event-proxy");
+    authPayload.put("provider", "com.example");
+    TokenGenerator tokenGenerator = new TokenGenerator(firebaseSecret);
+    return tokenGenerator.createToken(authPayload);
+  }
+}

appengine/firebase-event-proxy/gae-firebase-event-proxy/src/main/java/com/example/GaeFirebaseEventProxy/ServletContextListenerImpl.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 java.util.logging.Logger;
+
+import javax.servlet.ServletContextEvent;
+import javax.servlet.ServletContextListener;
+
+// ServletContextListener that is called whenever your App Engine app starts up.
+public class ServletContextListenerImpl implements ServletContextListener {
+
+  private static final Logger log = Logger.getLogger(ServletContextListener.class.getName());
+
+  @Override
+  public void contextInitialized(ServletContextEvent event) {
+    log.info("Starting ....");
+    FirebaseEventProxy proxy = new FirebaseEventProxy();
+    proxy.start();
+  }
+
+  @Override
+  public void contextDestroyed(ServletContextEvent event) {
+    // App Engine does not currently invoke this method.
+  }
+}