Java 7 runtime support on App Engine standard was deprecated on December 13, 2017 and will be shut down entirely on January 16, 2019. It is replaced by the Java 8 Runtime Environment.
Samples for the Java 8 runtime can be found here.
This directory contains Google Cloud Endpoints Frameworks for App Engine for
App Engine Standard samples. The backend/ directory contains the
sample code for the quickstart for Cloud Endpoints Frameworks on App Engine
using an OpenAPI development process. The migration-example/ directory
contains the sample code for a migrated version of the Cloud Endpoints
Frameworks sample project to the new [Cloud Endpoints Frameworks for App Engine][8]
development process.
The new Google Cloud Endpoints Frameworks for App Engine provides additional functionality using OpenAPI which may require payment. It's recommended that you migrate projects using the prior version of Cloud Endpoints Frameworks.