Purpose

To illustrate how to use Remote API in a local Java console app to access Google App Engine (GAE) services remotely.

Prerequisite

A valid GAE application with Remote API enabled is required. [1]

The Remote API client will rely on Application Default Credentials that use OAuth 2.0.

In order to get a credential run:

gcloud auth application-default login

To run the app

mvn exec:java -Dexec.mainClass=wua.eg.gae.remoteapi.App -Dexec.args="$GAE_HOST"

where $GAE_HOST is the remote GAE host. It can be localhost or xxxx.appspot.com

Alternatively, we could also copy the required dependency libraries with Maven and then run the app with the java command directly without Maven.

For example,

# Copy dependency libraries to folder ./target/
mvn -DoutputDirectory=target dependency:copy-dependencies

# Run it (with .class and .jar files in classpath, the main class, and arguments)
java -cp target/classes/:target/* wua.eg.gae.remoteapi.App $GAE_HOST

Make sure to replace $GAE_HOST with the actual GAE hostname (e.g. xxxx.appspot.com or localhost for local development server)

Maven Template used

mvn archetype:generate \
 -DgroupId=wua \
 -DartifactId=gae-remote-api-console-app \
 -Dpackage=wua.eg.gae.remoteapi \
 -DarchetypeArtifactId=maven-archetype-quickstart \
 -DinteractiveMode=false

Reference

[1] Remote API for Java https://cloud.google.com/appengine/docs/java/tools/remoteapi