Unrecognized element <app-engine-apis> in Google App Engine Java 11+ server deployment

Google Cloud Cloud Foundations & Onboarding
1

I finally migrated a long-running Google App Engine Java 8 project to Java 11+ standard environment before loss of Java 8 support in Jan 2024.

But I need to use the legacy bundled services including Datastore, Blobstore and Task Queues. I should do this by ‘Installing the App Engine API Jar.’

I followed the following Google tutorial https://cloud.google.com/appengine/docs/standard/java-gen2/services/access

In particular I need to ‘Install the App Engine API JAR’ by adding the following to the app-engine.web.xml file:

true

But trying to build/deploy the project via the Gradle plugin in Android Studio gets the exception ‘Unrecognized element ’.

So alas - I can’t deploy to the new Java 11 server environment while preserving the old bundled legacy functions.

Note: because I use the Gradle plugin with Android Studio to build and deploy the server, I don’t have a pom.xml file used by Maven.

Any advice on how to build the gradle file using the necessary ‘true’ would be greatly appreciated! Specs below:

Android Studio Giraffe 2022.3.1 Patch 4 with Gradle 7.4.2

Running server on GAE Standard Environment with Objectify 5

AppEngine Gradle file

apply **plugin**: **'java'**
apply **plugin**: **'war'**
apply **plugin**: **'com.google.cloud.tools.appengine'**
apply **plugin**: **'com.google.cloud.tools.endpoints-framework-server'**

buildscript **{**
 repositories **{**
 google()
        mavenCentral()
    **}**
 dependencies **{**
 classpath **'com.google.cloud.tools:endpoints-framework-gradle-plugin:2.1.0'**
 classpath **'com.google.cloud.tools:appengine-gradle-plugin:2.4.2'**
 **}**
**}**

repositories **{**
 google()
    mavenCentral()
**}**

appengine **{**
 deploy **{**
 version = **"GCLOUD_CONFIG"**
 projectId = **"GCLOUD_CONFIG"**
**    }**
**}**

sourceCompatibility = JavaVersion.<strong>*VERSION_11*</strong>
targetCompatibility = JavaVersion.<strong>*VERSION_11*</strong>

dependencies **{**
 implementation (**group**: **'com.google.appengine'**, **name**: **'appengine-api-1.0-sdk'**, **version**: **'2.0.0'**)
 implementation **'com.google.endpoints:endpoints-framework:2.2.2'**
 implementation (**'com.google.http-client:google-http-client-gson:1.40.1'**) **{**
 exclude (**group**: **'httpclient'**, **module**: **'httpclient'**)
    **}**
 implementation **'javax.inject:javax.inject:1'**
 implementation **'javax.servlet:servlet-api:3.0-alpha-1'**
 implementation **'javax.activation:javax.activation-api:1.2.0'**
 implementation (**'com.google.firebase:firebase-admin:8.1.0'**) **{**
 exclude (**group**: **'com.google.guava'**)
    **}**
 implementation **'com.google.guava:guava:31.0.1-jre'**
 implementation (**group**: **'com.google.appengine.tools'**, **name**: **'appengine-gcs-client'**, **version**: **'0.8.2'**)
 implementation **'com.googlecode.objectify:objectify:5.1.25'**
 implementation **"com.stripe:stripe-java:20.90.0"**
**}**

app-engine.web.xml

*<?***xml version="1.0" encoding="utf-8"***?>*
<**appengine-web-app xmlns="http://appengine.google.com/ns/1.0"**>
    <**application**>my-fashion-project</**application**>
    <**version**>1</**version**>
    <**runtime**>java11</**runtime**>
    <**app-engine-apis**>true</**app-engine-apis**>   // THIS IS THE LINE THAT CAUSES EXCEPTION
    <**threadsafe**>true</**threadsafe**>
    <**url-stream-handler**>urlfetch</**url-stream-handler**>

    <**system-properties**>
        <**property name="java.util.logging.config.file" value="WEB-INF/logging.properties"** />
    </**system-properties**>

    <**sessions-enabled**>
        true
    </**sessions-enabled**>

    <**resource-files**>
        <__include path="/**.json"__ />
    </**resource-files**>

    <**automatic-scaling**>
        <**min-instances**>1</**min-instances**>
    </**automatic-scaling**>

</**appengine-web-app**>

web.xml

*<?***xml version="1.0" encoding="utf-8"***?>*
<**web-app xmlns="http://java.sun.com/xml/ns/javaee" version="2.5"**>
    <**app-engine-apis**>true</**app-engine-apis**>

    <**filter**>
        <**filter-name**>ObjectifyFilter</**filter-name**>
        <**filter-class**>com.googlecode.objectify.ObjectifyFilter</**filter-class**>
    </**filter**>
    <**filter-mapping**>
        <**filter-name**>ObjectifyFilter</**filter-name**>
        <**url-pattern**>/*</**url-pattern**>
    </**filter-mapping**>

    <**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**>
                com.myfashionserver.entities.MemberEndpoint,
                ............ (list of entity endpoints excluded) ............ 
            </**param-value**>
        </**init-param**>
    </**servlet**

    <**servlet-mapping**>
............ (list of servlets excluded) ............

 <**security-constraint**>
        <**web-resource-collection**>
            <**web-resource-name**>queue</**web-resource-name**>
            <**url-pattern**>/queue/*</**url-pattern**>
        </**web-resource-collection**>
        <**auth-constraint**>
            <**role-name**>admin</**role-name**>
        </**auth-constraint**>
    </**security-constraint**>
    <**welcome-file-list**>
        <**welcome-file**>blog.html</**welcome-file**>
    </**welcome-file-list**>
</**web-app**>

Android Studio Gradle build exception log

com.google.apphosting.utils.config.AppEngineConfigException: Unrecognized element <app-engine-apis>
at com.google.apphosting.utils.config.AppEngineWebXmlProcessor.processSecondLevelNode(AppEngineWebXmlProcessor.java:243)
at com.google.apphosting.utils.config.AppEngineWebXmlProcessor.processXml(AppEngineWebXmlProcessor.java:64)
at com.google.apphosting.utils.config.AppEngineWebXmlReader.processXml(AppEngineWebXmlReader.java:132)
at com.google.apphosting.utils.config.AppEngineWebXmlReader.readAppEngineWebXml(AppEngineWebXmlReader.java:76)
at com.google.api.server.spi.tools.AppEngineUtil.getAppProperty(AppEngineUtil.java:138)
at com.google.api.server.spi.tools.AppEngineUtil.getApplicationId(AppEngineUtil.java:57)
at com.google.api.server.spi.tools.AppEngineUtil.getApplicationDefaultHostname(AppEngineUtil.java:96)
at com.google.api.server.spi.tools.EndpointsToolAction.getHostname(EndpointsToolAction.java:233)
at com.google.api.server.spi.tools.GetDiscoveryDocAction.execute(GetDiscoveryDocAction.java:85)
at com.google.api.server.spi.tools.EndpointsTool.execute(EndpointsTool.java:84)
at com.google.cloud.tools.gradle.endpoints.framework.server.task.EndpointsArtifactTask.generateEndpointsArtifact(EndpointsArtifactTask.java:208)
at java.base@17.0.6/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base@17.0.6/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at java.base@17.0.6/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.base@17.0.6/java.lang.reflect.Method.invoke(Unknown Source)
at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:125
at org.gradle.api.internal.project.taskfactory.StandardTaskAction.doExecute(StandardTaskAction.java:58)
at org.gradle.api.internal.project.taskfactory.StandardTaskAction.execute(StandardTaskAction.java:51)
at org.gradle.api.internal.project.taskfactory.StandardTaskAction.execute(StandardTaskAction.java:29)
at org.gradle.api.internal.tasks.execution.TaskExecution$3.run(TaskExecution.java:236)
at org.gradle.internal.operations.DefaultBuildOperationRunner$1.execute(DefaultBuildOperationRunner.java:29)
at org.gradle.internal.operations.DefaultBuildOperationRunner$1.execute(DefaultBuildOperationRunner.java:26)
at org.gradle.internal.operations.DefaultBuildOperationRunner$2.execute(DefaultBuildOperationRunner.java:66)
at org.gradle.internal.operations.DefaultBuildOperationRunner$2.execute(DefaultBuildOperationRunner.java:59)
at org.gradle.internal.operations.DefaultBuildOperationRunner.execute(DefaultBuildOperationRunner.java:157)
at org.gradle.internal.operations.DefaultBuildOperationRunner.execute(DefaultBuildOperationRunner.java:59)
at org.gradle.internal.operations.DefaultBuildOperationRunner.run(DefaultBuildOperationRunner.java:47)
at org.gradle.internal.operations.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:68)
at org.gradle.api.internal.tasks.execution.TaskExecution.executeAction(TaskExecution.java:221)
at org.gradle.api.internal.tasks.execution.TaskExecution.executeActions(TaskExecution.java:204)
at org.gradle.api.internal.tasks.execution.TaskExecution.executeWithPreviousOutputFiles(TaskExecution.java:187)
at org.gradle.api.internal.tasks.execution.TaskExecution.execute(TaskExecution.java:165)
at org.gradle.internal.execution.steps.ExecuteStep.executeInternal(ExecuteStep.java:89)
at org.gradle.internal.execution.steps.ExecuteStep.access$000(ExecuteStep.java:40)
at org.gradle.internal.execution.steps.ExecuteStep$1.call(ExecuteStep.java:53)
at org.gradle.internal.execution.steps.ExecuteStep$1.call(ExecuteStep.java:50)

App Engine server exception log when trying to call API methods that use Datastore with Objectify 5. Error occurs when deployed the project in the Java 11+ environment without the true line in app-engine.web.xml.

exception occurred while calling backend method
com.google.apphosting.api.ApiProxy$FeatureNotEnabledException: datastore_v3.RunQuery 
 at com.google.apphosting.utils.runtime.ApiProxyUtils.convertApiError(ApiProxyUtils.java:81)
 at com.google.apphosting.utils.runtime.ApiProxyUtils.getApiError(ApiProxyUtils.java:198)
 at com.google.apphosting.runtime.ApiProxyImpl$AsyncApiFuture.success(ApiProxyImpl.java:684)
 at com.google.apphosting.runtime.ApiProxyImpl$AsyncApiFuture.success(ApiProxyImpl.java:581)
 at com.google.apphosting.runtime.http.HttpApiHostClient.receivedResponse(HttpApiHostClient.java:296)
 at com.google.apphosting.runtime.http.JettyHttpApiHostClient$Listener.onComplete(JettyHttpApiHostClient.java:206)
 at org.eclipse.jetty.client.ResponseNotifier.notifyComplete(ResponseNotifier.java:218)
 at org.eclipse.jetty.client.ResponseNotifier.notifyComplete(ResponseNotifier.java:210)
 at org.eclipse.jetty.client.HttpReceiver.terminateResponse(HttpReceiver.java:481)
 at org.eclipse.jetty.client.HttpReceiver.terminateResponse(HttpReceiver.java:461)
 at org.eclipse.jetty.client.HttpReceiver.responseSuccess(HttpReceiver.java:424)
 at org.eclipse.jetty.client.http.HttpReceiverOverHTTP.messageComplete(HttpReceiverOverHTTP.java:374)
 at org.eclipse.jetty.http.HttpParser.handleContentMessage(HttpParser.java:596)
 at org.eclipse.jetty.http.HttpParser.parseContent(HttpParser.java:1723)
 at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:1552)
 at org.eclipse.jetty.client.http.HttpReceiverOverHTTP.parse(HttpReceiverOverHTTP.java:208)
 at org.eclipse.jetty.client.http.HttpReceiverOverHTTP.process(HttpReceiverOverHTTP.java:148)
 at org.eclipse.jetty.client.http.HttpReceiverOverHTTP.receive(HttpReceiverOverHTTP.java:80)
 at org.eclipse.jetty.client.http.HttpChannelOverHTTP.receive(HttpChannelOverHTTP.java:131)
 at org.eclipse.jetty.client.http.HttpConnectionOverHTTP.onFillable(HttpConnectionOverHTTP.java:172)
 at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:311)
 at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:105)
 at org.eclipse.jetty.io.ChannelEndPoint$1.run(ChannelEndPoint.java:104)
 at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
 at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
 at java.base/java.lang.Thread.run(Thread.java:829)

I assume this GAE exception is thrown because the server can’t access the legacy Datastore due to failure to ‘Install the App Engine API JAR’. The alternative explanation is that I am not using Objectify 6, but I have read that others are running Java 11+ GAE servers with Objectify 5.

2

So I’ll post the answer to this problem in case anyone else is also trying to update their GAE project to Java 11+ and tries to use the Legacy Bundled services and encounters the inability to build their App Engine standard project when using true in the appengine-web.xml file.

The problem is my GAE server project was using the original Cloud Endpoints Frameworks that conveniently created the server API stubs for the server and Android device client (see https://cloud.google.com/endpoints/docs/frameworks/about-cloud-endpoints-frameworks).

However Cloud Endpoints Framework uses the Java 8 environment. The project is ‘dead’ on Github and has been abandoned for the newer Google Endpoints that uses the OpenAPI protocol.

So the problem was actually in the web.xml file where I specified the Endpoints servlet class to build the Endpoints servlets:

<servlet-class>com.google.api.server.spi.EndpointsServlet</servlet-class>

This servlet specification is required for the old Cloud Endpoints Framework along with the build.gradle dependency:

implementation 'com.google.endpoints:endpoints-framework:2.2.2'

Using this framework prevents the true specification in the appengine-web.xml. The project won’t build.

My solution: I just couldn’t use the Legacy Bundled Services and instead was forced to update the GAE server to use the new Google Cloud Client Libraries with Cloud Storage and Datastore in Firebase. The server database was already under the Firebase Datastore environment.

However what isn’t clearly stated is that if you want to use Objectify with the newer Cloud Client Libraries, you must update the Objectify version to 6. Any Objectify version under 6 will not work with the Cloud Client Libraries.

I believe this is good for the long run, because Google will eventually abandoned the Legacy Bundled services, and it would be foolish to build an entire database based on old APIs. I am still using the Cloud Endpoints framework to build and deploy the project in a Java 17 environment now. Eventually I’ll have to implement the new Cloud Endpoints with openAPI but this will require a total rehaul of the Android, iPhone and web page client code - a very daunting task that will ‘kill’ any old versions of the client apps.

Hope this helps anyone in the same dilemma.

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