Google cloud App engine Spring deploy error

Question

Im trying to deploy a springboot rest api to google cloud's app engine, following this recent tutorial: https://medium.com/@smccartney09/deploy-a-spring-boot-api-to-gcp-app-engine-722198bab4d4and

However i'm getting this error:

org.springframework.context.ApplicationContextException: Unable to start ServletWebServerApplicationContext due to missing ServletWebServerFactory bean.

The app runs normally in localhost, from what I can see trying to debug, on localhost springboot launches a tomcat web server, and it doesn't in the logs form google app run deployment. Does this mean I have to use google's web server instead of tomcat? i'm really lost as to what i'm doing wrong right now.

POM xml:

<parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.4.1</version>
        <relativePath/>
    </parent>
    <groupId>com.owl</groupId>
    <artifactId>owl-server</artifactId>
    <version>0.0</version>
    <name>owl-server</name>
    <description>owl backend server</description>

    <properties>
        <java.version>11</java.version>
    </properties>

    <dependencies>

        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-collections4</artifactId>
            <version>4.4</version>
        </dependency>
        <dependency>
            <groupId>org.modelmapper</groupId>
            <artifactId>modelmapper</artifactId>
            <version>2.3.9</version>
        </dependency>
        <dependency>
            <groupId>io.vavr</groupId>
            <artifactId>vavr</artifactId>
            <version>0.10.3</version>
        </dependency>
        <dependency>
            <groupId>commons-beanutils</groupId>
            <artifactId>commons-beanutils</artifactId>
            <version>1.9.4</version>
        </dependency>

        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>3.12.0</version>
        </dependency>


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

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-gcp-starter-sql-mysql</artifactId>
            <version>1.2.8.RELEASE</version>
        </dependency>

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

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

main:

@SpringBootApplication
@EnableCaching
public class OwlServerApplication {

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

    }

Ok, so after a lot of reading i think it might be because google app engine doesnt support tomcat as a webserver, and instead only supports jetty? so i tried the following:

added to pom xml:

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

but this does nothing, same exact error. I then tried to add jetty as well, which runs locally great as a jetty web server, but gives the same error on app engine. So we know the error is due to google app engine not supporting tomcat or jetty, but what do i use now? Anyone have any idea on whats going wrong?

Answer 1

So after a lot of debugging, the problem here lies in spring security. If you have a class that extends WebSecurityConfigurerAdapter, spring will automatically attempt to use apply it to the embedded tomcat web server. Which is not supported on google app engine, which broke it. Just remove the class and the app will work.