Google App Engine Standard env - not found controller method - Spring Boot app

Question

I was trying to deploy Spring Boot application on Google App Engine (standard environment). At first I cloned example app from this nice tutorial https://springframework.guru/spring-boot-web-application-part-4-spring-mvc/

For example I called http://localhost:8080/products and template with data was displayed.

So everything ran without problems, I was able to call all controller methods locally. Then I decided as experiment to deploy it on GAE. I adjusted pom.xml according to instructions from here https://github.com/GoogleCloudPlatform/getting-started-java/tree/master/appengine-standard-java8/springboot-appengine-standard

It means I excluded Tomcat dependency, changed packaging from jar to war, created appengine-web.xml file etc. As next step, I created GAE project in GAE console and copied APP ID into appengine-web.xml. Then I ran mvn clean package and war was created in target folder. Finally I started with GAE deployment and it also went smoothly without errors.

My app is now deployed on this URL https://20180109t135551-dot-oe-gae-test.appspot.com/

If you try it, you will see Hello World in browser. But if I try to call /products controller method like this https://20180109t135551-dot-oe-gae-test.appspot.com/products I get "not found" error.

Can you give me advice on which URL should I call my controller methods? Did I forget to implement something like web.xml servlet mapping? Or is it some specific Spring Boot - Google App Engine problem?

I will be grateful for any hint.

Thank you all in advance

Answer 1

Following this steps translates into the following for the code:

1. In pom.xml, change <packaging>jar</packaging> to <packaging>war</packaging>

2. In the package guru.springframework add this class:

Code:

package guru.springframework;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class SpringBootWebApplication {

public static void main(String[] args) {
        SpringApplication.run(SpringBootWebApplication.class, args);
    }
}    

3. Remove Tomcat Starter:

Find this dependency in the POM:

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

And add these lines:

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
        <exclusions>
            <exclusion>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-tomcat</artifactId>
            </exclusion>
        </exclusions>
    </dependency>

4. Exclude Jetty dependencies and include the Servlet API dependency:

   <dependency> <groupId>javax.servlet</groupId> <artifactId>javax.servlet-api</artifactId> <version>3.1.0</version> <scope>provided</scope> </dependency>

5. Add the App Engine Standard plugin:

   <plugin>
       <groupId>com.google.cloud.tools</groupId>
       <artifactId>appengine-maven-plugin</artifactId>
       <version>1.3.1</version>
   </plugin>
   

   6. Add a file called appengine-web.xml in src/webapp/WEB-INF with these contents:

   <appengine-web-app xmlns="http://appengine.google.com/ns/1.0"> <threadsafe>true</threadsafe> <runtime>java8</runtime> </system-properties> </appengine-web-app>

   7. Exclude JUL to SLF4J Bridge by locating this dependency in the pom:

   <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> </dependency>

and modifying it this way:

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
        <exclusions>
            <exclusion>
                <groupId>org.slf4j</groupId>
                <artifactId>jul-to-slf4j</artifactId>
            </exclusion>
        </exclusions>
    </dependency>

8. Avoiding out of memory errors:

In src/main/resources add a logging.properties file with:

.level = INFO

and inside src/main/webapp/WEB-INF/appengine-web.xml paste this:

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

EDIT:

For steps 3 and 7 you can also go to the project explorer (in case you're using Eclipse) and navigate to Libraries -> Maven dependencies and select each library individually (jul-to-slf4j-1.7.25 and spring-boot-starter-tomcat-1.5.3.RELEASE in my case). Right click on each library and go to Maven -> Exclude Maven artifact... And click Ok. This will have the same effect on the POM as editing.