Setting up Android Studio with Cloud Endpoints Frameworks (Cloud Endpoints v2.0)

This blog article demonstrates how to get started with App Engine’s Cloud Endpoints Framwork v2.0 in Android Studio and details configuration necessary for migration from version 1.0 of App Engine Cloud Endpoints.

Selecting a cloud platform serving as backend for an Android or web application can be tedious, there are numerous services such as Heroku, Amazon AWS, Google App Engine as well as providers offering hosting for Docker containers.

While there are a large variety of factors that should influence your decision of choosing the right platform, such as how complex maintenance is, how price compares and how much many ties there are to any given platform that might lock you in, it is still tempting to go ahead and just try out a platform that offers the most convenience.

Thus, when developing Android applications in Android Studio it is quite difficult to oversee the apparent ease of integration into Google App Engine.

One of the most convenient features of writing backend code in Java when using it together with an Android application, is the reuse of class code that is shared between the Android client application and the server side code.

When checking the “New Module” dialog in Android Studio, there are a couple of different ways to set up an App Engine service. The option “App Engine Java Endpoints Module” seems to offer an impressive set of features, among them Security (+ Authentication), Monitoring, Performance.

Having spent a good amount of time to understand how user registration, authentication and account maintenance in a web application work, it becomes apparent that not only implementation is very effort intensive, also storing and accessing user data in a secure and save way proves to be a challenge as well.

Especially maintaining data such as passwords and private user information in a secure way can lead to large overhead for a startup project. The solution for this is to use 3rd party authentication services and even better, to let users log in by using existing one of their accounts such as their Google Login, Facebook, Twitter or Github service. One of the 3rd parties offering ease of access is “Firebase Auth”. And coincidentally they also offer integration into App Engine Cloud Endpoints.

Now of course it goes without saying, that when using a service like that, the application will heavily rely on the existence of the 3rd party service, meaning that if for some reason the provider shuts down or has issues with their service, the users will most probably will not be able to log into the web application depending on authentication.

Set aside all the considerations and fears of using any services at all, let’s dive into setting up a project with Google Cloud Endpoints.

https://cloud.google.com/endpoints/

One of the first things to notice is that currently there seems to be two versions of Cloud Endpoints available. The most recent iteration (at the time of this writing version 2.0) promises improvements of performance, reduced latency, more features. The only caveat, currently Android Studio sets up a Cloud Endpoints module with version 1.0. Of course this is utterly unacceptable you might agree, which is why migrating to version 2.0 is the only real option.

This article will help you to get started to get your Android Application and the Cloud Endpoints Framework v2.0 running on a local development server. Setting up a Google App Engine account for the purpose of local debugging is not even necessary.

While there are official guides that help migration to Cloud Endpoints v2.0 they don’t really address how to do this in Android Studio, let alone with gradle, thus this guide will try to fill the gap by guiding the reader through the process of setting up a new project.

Let’s get started.

Creating an Android Application with a Cloud Endpoints Module

First create a new Android Application Project inside Android Studio with an Empty Activity.

Your Project should look like in the image below.

After Gradle is synced, add a new module of the type “App Engine Java Cloud Endpoints Module”.

After the module is created, be sure to wait until Gradle syncs (possibly hit the gradle sync button above, or go to Tools > Android > Sync Project with Gradle Files.

You will notice that besides the new module, there is also a new gradle build file for “backend” available.

Open it in Android Studio and replace its contents with the ones below:

Use the gradle code available here:

https://github.com/GoogleCloudPlatform/java-docs-samples/blob/master/appengine/endpoints-frameworks-v2/migration-example/build.gradle

// Copyright 2017 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.

// [START buildscript]
buildscript {    // Configuration for building
  repositories {
    mavenCentral()
    jcenter()    // Bintray's repository - a fast Maven Central mirror & more
  }
  dependencies {
    // App Engine Gradle plugin
    classpath 'com.google.cloud.tools:appengine-gradle-plugin:1.3.0'

    // Endpoints Frameworks Gradle plugin
    classpath 'com.google.cloud.tools:endpoints-framework-gradle-plugin:1.0.0-beta9'
  }
}
// [END buildscript]

repositories {   // repositories for Jar's you access in your code
  mavenCentral()
  jcenter()
}

apply plugin: 'java'                              // standard Java tasks
apply plugin: 'war'                               // standard Web Archive plugin

// [START apply_appengine]
apply plugin: 'com.google.cloud.tools.appengine'  // App Engine tasks
// [END apply_appengine]

// [START apply_endpoints-framework-server]
apply plugin: 'com.google.cloud.tools.endpoints-framework-server'
// [END apply_endpoints-framework-server]

dependencies {
  providedCompile group: 'javax.servlet', name: 'servlet-api', version:'2.5'
  compile 'jstl:jstl:1.2'
  compile group: 'javax.inject', name: 'javax.inject', version: '1'

  // Uncomment to use Endpoints Frameworks v1.0
  // compile group: 'com.google.appengine', name: 'appengine-endpoints', version: '1.9.48'
  // End of Endpoints Frameworks v1.0

  // Endpoints Frameworks v2.0
  // [START endpoints-tools]
  compile group: 'com.google.endpoints', name: 'endpoints-framework-tools', version: '2.0.7'
  // [END endpoints-tools]
  // End of Endpoints Frameworks v2.0
}

appengine {  // App Engine tasks configuration
  deploy {   // deploy configuration
    version = findProperty("appengine.deploy.version")

    def promoteProp = findProperty("appengine.deploy.promote")
    if (promoteProp != null) {
      promote = new Boolean(promoteProp)
    }
  }
}

/* [START endpoints-server]
endpointsServer {
  // Endpoints Framework Plugin server-side configuration
}
[END endpoints-server] */

group   = 'com.example.helloendpoints' // Generated output GroupId
version = '1'                          // Version in generated output

sourceCompatibility = 1.7     // App Engine Standard uses Java 7
targetCompatibility = 1.7     // App Engine Standard uses Java 7

After replacing the Gradle Build Script you will receive an error pointing out that the Android module cannot find the corresponding build configuration.

Error:Project :app declares a dependency from configuration 'compile' to configuration 'android-endpoints' which is not declared in the descriptor for project :backend.

In order to fix that, go into the “app” Gradle build script and adjust the following lines under “dependencies”.

# build.gradle (app)
compile project(path: ':backend', configuration: 'android-endpoints')

change it to

# build.gradle (app)
compile project(path: ':backend', configuration: 'android-backend')

Let Gradle sync. Now a new issue will arise, throwing following exception:

Error:Execution failed for task ':backend:endpointsDiscoveryDocs'.
> com.google.common.reflect.TypeToken.isSubtypeOf(Ljava/lang/reflect/Type;)Z

In order to fix the issue, open the Gradle build file of the module “CloudApp” and place the first dependency lines of the backend Gradle inside it in order for it to look like the code below.

// Top-level build file where you can add configuration options common to all sub-projects/modules.

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:2.3.1'

        classpath 'com.google.cloud.tools:appengine-gradle-plugin:1.3.0'

        // Endpoints Frameworks Gradle plugin
        classpath 'com.google.cloud.tools:endpoints-framework-gradle-plugin:1.0.0-beta9'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

After Running a clean via Build > Clean Project and hitting the build button (hammer symbol) there will be yet again an Error.

Error running backend: Cannot start process, the working directory '/home/mdc/aw/CloudApp/backend/build/exploded-app' does not exist

It seems the WAR dir is not properly configured. Make sure to be in the “Project Files” perspective and navigate into the backend.iml File.

<option name="WAR_DIR" value="$MODULE_DIR$/build/exploded-app" />

The above line needs to be changed into

<option name="WAR_DIR" value="$MODULE_DIR$/build/exploded-backend" />

Again, hit Clean and Build. Afterwards hit the Run button just on the right of it. Possibly if you have a service running already on port 8080, you will need to adjust the settings of the development server. Following error will be shown if you cannot start the server on port 8080:

Could not open the requested socket: Address already in use
Try overriding --address and/or --port.

In order to change the port we need to adjust the Android Studio project settings for the backend project.
Therefore, change into the “Project Files” view and navigate to backend > backend > backend.iml.

Find the HTTP_PORT parameter and change it accordingly. Also if you later want to access the backend from your local network, change the http address from “localhost” to “0.0.0.0”.

<option name="HTTP_ADDRESS" value="localhost" />
<option name="HTTP_PORT" value="8080" />

<option name="HTTP_PORT" value="9292" />
<option name="HTTP_ADDRESS" value="0.0.0.0" />

Once more hit clean, then build and run.

In the “Run” tab you will notice a couple of exceptions.

WARNING: EXCEPTION 
java.lang.ClassNotFoundException: com.google.api.server.spi.SystemServiceServlet
	at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at com.google.appengine.tools.development.IsolatedAppClassLoader.loadClass(IsolatedAppClassLoader.java:198)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	at org.mortbay.util.Loader.loadClass(Loader.java:91)
	at org.mortbay.util.Loader.loadClass(Loader.java:71)
	at org.mortbay.jetty.servlet.Holder.doStart(Holder.java:73)
	at org.mortbay.jetty.servlet.ServletHolder.doStart(ServletHolder.java:242)
	at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
	at org.mortbay.jetty.servlet.ServletHandler.initialize(ServletHandler.java:685)
	at org.mortbay.jetty.servlet.Context.startContext(Context.java:140)
	at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1250)
	at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:517)
	at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:467)
	at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
	at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:130)
	at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
	at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:130)
	at org.mortbay.jetty.Server.doStart(Server.java:224)
	at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
	at com.google.appengine.tools.development.JettyContainerService.startContainer(JettyContainerService.java:271)
	at com.google.appengine.tools.development.AbstractContainerService.startup(AbstractContainerService.java:284)
	at com.google.appengine.tools.development.AutomaticInstanceHolder.startUp(AutomaticInstanceHolder.java:26)
	at com.google.appengine.tools.development.AbstractModule.startup(AbstractModule.java:87)
	at com.google.appengine.tools.development.Modules.startup(Modules.java:105)
	at com.google.appengine.tools.development.DevAppServerImpl.doStart(DevAppServerImpl.java:262)
	at com.google.appengine.tools.development.DevAppServerImpl.access$000(DevAppServerImpl.java:45)
	at com.google.appengine.tools.development.DevAppServerImpl$1.run(DevAppServerImpl.java:217)
	at com.google.appengine.tools.development.DevAppServerImpl$1.run(DevAppServerImpl.java:215)
	at java.security.AccessController.doPrivileged(Native Method)
	at com.google.appengine.tools.development.DevAppServerImpl.start(DevAppServerImpl.java:215)
	at com.google.appengine.tools.development.DevAppServerMain$StartAction.apply(DevAppServerMain.java:277)
	at com.google.appengine.tools.util.Parser$ParseResult.applyArgs(Parser.java:48)
	at com.google.appengine.tools.development.DevAppServerMain.run(DevAppServerMain.java:225)
	at com.google.appengine.tools.development.DevAppServerMain.main(DevAppServerMain.java:216)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)

May 13, 2017 4:29:48 PM com.google.appengine.tools.development.ApiProxyLocalImpl log
SEVERE: javax.servlet.ServletContext log: unavailable
javax.servlet.UnavailableException: com.google.api.server.spi.SystemServiceServlet
	at org.mortbay.jetty.servlet.Holder.doStart(Holder.java:79)
	at org.mortbay.jetty.servlet.ServletHolder.doStart(ServletHolder.java:242)
	at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
	at org.mortbay.jetty.servlet.ServletHandler.initialize(ServletHandler.java:685)
	at org.mortbay.jetty.servlet.Context.startContext(Context.java:140)
	at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1250)
	at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:517)
	at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:467)
	at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
	at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:130)
	at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
	at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:130)
	at org.mortbay.jetty.Server.doStart(Server.java:224)
	at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
	at com.google.appengine.tools.development.JettyContainerService.startContainer(JettyContainerService.java:271)
	at com.google.appengine.tools.development.AbstractContainerService.startup(AbstractContainerService.java:284)
	at com.google.appengine.tools.development.AutomaticInstanceHolder.startUp(AutomaticInstanceHolder.java:26)
	at com.google.appengine.tools.development.AbstractModule.startup(AbstractModule.java:87)
	at com.google.appengine.tools.development.Modules.startup(Modules.java:105)
	at com.google.appengine.tools.development.DevAppServerImpl.doStart(DevAppServerImpl.java:262)
	at com.google.appengine.tools.development.DevAppServerImpl.access$000(DevAppServerImpl.java:45)
	at com.google.appengine.tools.development.DevAppServerImpl$1.run(DevAppServerImpl.java:217)
	at com.google.appengine.tools.development.DevAppServerImpl$1.run(DevAppServerImpl.java:215)
	at java.security.AccessController.doPrivileged(Native Method)
	at com.google.appengine.tools.development.DevAppServerImpl.start(DevAppServerImpl.java:215)
	at com.google.appengine.tools.development.DevAppServerMain$StartAction.apply(DevAppServerMain.java:277)
	at com.google.appengine.tools.util.Parser$ParseResult.applyArgs(Parser.java:48)
	at com.google.appengine.tools.development.DevAppServerMain.run(DevAppServerMain.java:225)
	at com.google.appengine.tools.development.DevAppServerMain.main(DevAppServerMain.java:216)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)

May 13, 2017 4:29:48 PM com.google.apphosting.utils.jetty.JettyLogger warn
WARNING: failed SystemServiceServlet: java.lang.NullPointerException
May 13, 2017 4:29:48 PM com.google.apphosting.utils.jetty.JettyLogger warn
WARNING: Failed startup of context com.google.appengine.tools.development.DevAppEngineWebAppContext@2e3967ea{/,/home/mdc/aw/CloudApp/backend/build/exploded-backend}
java.lang.NullPointerException
	at java.lang.Class.isAssignableFrom(Native Method)
	at org.mortbay.jetty.servlet.ServletHolder.doStart(ServletHolder.java:256)
	at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
	at org.mortbay.jetty.servlet.ServletHandler.initialize(ServletHandler.java:685)
	at org.mortbay.jetty.servlet.Context.startContext(Context.java:140)
	at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1250)
	at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:517)
	at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:467)
	at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
	at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:130)
	at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
	at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:130)
	at org.mortbay.jetty.Server.doStart(Server.java:224)
	at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
	at com.google.appengine.tools.development.JettyContainerService.startContainer(JettyContainerService.java:271)
	at com.google.appengine.tools.development.AbstractContainerService.startup(AbstractContainerService.java:284)
	at com.google.appengine.tools.development.AutomaticInstanceHolder.startUp(AutomaticInstanceHolder.java:26)
	at com.google.appengine.tools.development.AbstractModule.startup(AbstractModule.java:87)
	at com.google.appengine.tools.development.Modules.startup(Modules.java:105)
	at com.google.appengine.tools.development.DevAppServerImpl.doStart(DevAppServerImpl.java:262)
	at com.google.appengine.tools.development.DevAppServerImpl.access$000(DevAppServerImpl.java:45)
	at com.google.appengine.tools.development.DevAppServerImpl$1.run(DevAppServerImpl.java:217)
	at com.google.appengine.tools.development.DevAppServerImpl$1.run(DevAppServerImpl.java:215)
	at java.security.AccessController.doPrivileged(Native Method)
	at com.google.appengine.tools.development.DevAppServerImpl.start(DevAppServerImpl.java:215)
	at com.google.appengine.tools.development.DevAppServerMain$StartAction.apply(DevAppServerMain.java:277)
	at com.google.appengine.tools.util.Parser$ParseResult.applyArgs(Parser.java:48)
	at com.google.appengine.tools.development.DevAppServerMain.run(DevAppServerMain.java:225)
	at com.google.appengine.tools.development.DevAppServerMain.main(DevAppServerMain.java:216)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)

This is due to the new classes used of the servlet. Navigate into the webapp/WEB-INF/web.xml File and replace the contents as follows:

<?xml version="1.0" encoding="utf-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee">
    <servlet>
        <servlet-name>EndpointsServlet</servlet-name>
        <servlet-class>com.google.api.server.spi.EndpointsServlet</servlet-class>
        <init-param>
            <param-name>services</param-name>
            <param-value>ch.nexuscomputing.cloudapp.backend.MyEndpoint</param-value>
        </init-param>
        <init-param>
            <param-name>restricted</param-name>
            <param-value>false</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>EndpointsServlet</servlet-name>
        <url-pattern>/_ah/api/*</url-pattern>
    </servlet-mapping>
</web-app>

Note that the classname “ch.nexuscomputing.cloudapp.backend.MyEndpoint” needs to match your namespace in your backend module.

Hit Clean Project, Rebuild the backend and hit run once more.

Now if all goes well you can navigate in your browser to http://localhost:9292/ and see the web application running.

One more pro tip for debugging: don’t right away start coding the Android part, but try to access the web application from your android device’s browser via http://YOURIP:9292/, this will already rule out connection issues within your LAN.

This will set you up for starting to code your Android application and make full use of the “Cloud Endpoints Framework v2.0” features.

If you liked this tutorial make sure to give it a +1 and share it among your friends, we greatly appreciate all your support! Of course if you have questions or if a step in the guide is not working out for you, please let us know about it so we can keep the article up to date.