Deploying Spring Boot Applications on Google Application Engine (GAE)

I previously blogged about how to how to deploy a Spring Boot application to Flexible VM's on Google Cloud Platform as shown below.

http://theblasfrompas.blogspot.com.au/2016/09/spring-boot-on-google-cloud-platform-gcp.html

In this example below I use Google Application Engine (GAE) to deploy a Spring Boot application without using a flexible VM which is a lot faster and what I orginally wanted to do when I did this previously. In short this is using the [Standard environment] option for GAE.

Spring Boot uses Servlet 3.0 APIs to initialize the ServletContext (register Servlets etc.) so you can’t use the same application out of the box in a Servlet 2.5 container. It is however possible to run a Spring Boot application on an older container with some special tools. If you include org.springframework.boot:spring-boot-legacy as a dependency (maintained separately to the core of Spring Boot and currently available at 1.0.2.RELEASE), all you should need to do is create a web.xml and declare a context listener to create the application context and your filters and servlets. The context listener is a special purpose one for Spring Boot, but the rest of it is normal for a Spring application in Servlet 2.5

Visit for more Information:

   http://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#howto-servlet-2-5 

Steps

1. In order to use Servlet 2.5 and a web.xml we will need to add spring-boot-legacy dependecany to a local maven repoistory as shown below.

$ git clone https://github.com/scratches/spring-boot-legacy
$ cd spring-boot-legacy
$ mvn install

2. Clone and package the GIT REPO as shown below

$ https://github.com/papicella/GoogleAppEngineSpringBoot.git

3. Edit the file ./src/main/webapp/WEB-INF/appengine-web.xml to specify the correct APPLICATION ID which we will target in step 4 as well.

  
<?xml version="1.0" encoding="utf-8"?>
<appengine-web-app xmlns="http://appengine.google.com/ns/1.0">
 <application>fe-papicella</application>
 <version>5</version>
   <threadsafe>true</threadsafe>
 <manual-scaling>
  <instances>1</instances>
 </manual-scaling>
</appengine-web-app>

4. Package as shown below

$ mvn package

5. Target your project for deployment as follows

pasapicella@pas-macbook:~/piv-projects/GoogleAppEngineSpringBoot$ gcloud projects list
PROJECT_ID              NAME                    PROJECT_NUMBER
bionic-vertex-150302    AppEngineSpringBoot     97889500330
fe-papicella            FE-papicella            1049163203721
pas-spring-boot-on-gcp  Pas Spring Boot on GCP  1043917887789

pasapicella@pas-macbook:~/piv-projects/GoogleAppEngineSpringBoot$ gcloud config set project fe-papicella
Updated property [core/project].

6. Deploy as follows

mvn appengine:deploy

Finally once deployed you can access you application using it's endpoint which is displayed in the dashboard of GCP console

Project in InteiilJ IDEA

NOTE: Google AppEngine does not allow JMX, so you have to switch it off in a Spring Boot app (set spring.jmx.enabled=false in application.properties).

application.properties

spring.jmx.enabled=false

More Information

Full working example with code as follows on GitHub

https://github.com/papicella/GoogleAppEngineSpringBoot