SpringBoot API calls causing a 404, i have no access to my backend on tomcat9 server

Question

I have built a webapp using springboot with a react frontend and when I run the app locally I can use my REST API calls without any issue. Once I package everything up into a war file and deploy it to my tomcat server on my VM I can no longer access my backend.

On the catalina.out log file there are no errors appearing however theres also no indication of the springboot app starting. This is all I am getting.

17-Jul-2024 19:20:56.108 INFO [http-nio-0.0.0.0-8080-exec-2] org.apache.catalina.startup.HostConfig.deployWAR Deploying web application archive [/opt/tomcat/webapps/record-retention.war]
17-Jul-2024 19:20:56.305 WARNING [http-nio-0.0.0.0-8080-exec-2] org.apache.tomcat.util.descriptor.web.WebXml.setVersion Unknown version string [5.0]. Default version will be used.
17-Jul-2024 19:20:58.396 INFO [http-nio-0.0.0.0-8080-exec-2] org.apache.jasper.servlet.TldScanner.scanJars At least one JAR was scanned for TLDs yet contained no TLDs. Enable debug logging for this logger for a complete list of JARs that werening can improve startup time and JSP compilation time.
17-Jul-2024 19:20:58.416 INFO [http-nio-0.0.0.0-8080-exec-2] org.apache.catalina.startup.HostConfig.deployWAR Deployment of web application archive [/opt/tomcat/webapps/record-retention.war] has finished in [2,308] ms

This is my App class.

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;

@SpringBootApplication
public class App extends SpringBootServletInitializer{
 
    public static void main(String[] args) {    
        SpringApplication.run(App.class, args);  
    }

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application){
        return application.sources(App.class);
    }
}

The build portion of my pom.xml

<build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>

           <plugin>
            <groupId>com.github.eirslett</groupId>
            <artifactId>frontend-maven-plugin</artifactId>
            <version>1.12.1</version>
            <executions>
                <execution>
                    <id>Install node and npm</id>
                    <goals>
                        <goal>install-node-and-npm</goal>
                    </goals>
                    <configuration>
                        <nodeVersion>v20.14.0</nodeVersion>
                        <npmVersion>10.8.1</npmVersion>
                    </configuration>
                </execution>
                <execution>
                    <id>npm install</id>
                    <goals>
                        <goal>npm</goal>
                    </goals>
                    <phase>generate-resources</phase>
                    <configuration>
                        <arguments>install</arguments>
                        <workingDirectory>src/main/record-retention-ui</workingDirectory>
                    </configuration>
                </execution>
                <execution>
                    <id>npm build</id>
                    <goals>
                        <goal>npm</goal>
                    </goals>
                    <phase>generate-resources</phase>
                    <configuration>
                        <arguments>run build</arguments>
                        <workingDirectory>src/main/record-retention-ui</workingDirectory>
                    </configuration>
                </execution>
            </executions>
            <configuration>
                <workingDirectory>src/main/record-retention-ui</workingDirectory>
            </configuration>
        </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-resources-plugin</artifactId>
                <executions>
                    <execution>
                        <id>Copy JavaScript app into Springboot</id>
                        <phase>process-resources</phase>
                        <goals>
                            <goal>copy-resources</goal>
                        </goals>
                        <configuration>
                            <outputDirectory>${project.build.directory}/${project.build.finalName}/</outputDirectory>
                            <resources>
                                <resource>
                                    <directory>src/main/record-retention-ui/build</directory>
                                    <filtering>false</filtering>
                                </resource>
                            </resources>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

Previous to posting I've attacking this problem for 2 days with no avail, I implemented the servletInitializer as I didn't have that initially. I have no issue accessing the frontend through the server I just cant make any API calls.

This is my first time attempting to deploy a webapp to a server so any help/advice is greatly appreciated. If more information is needed I can provide it!

Answer 1

As shown here Spring Boot 3 comes with Jakarta EE 10 which means Servlet Specification 6.

As shown here for Servlet Spec 6 you need Tomcat 10.1+

Servlet Spec	Apache Tomcat Version	Supported Java Versions
6.1	11.0.x	17 and later
6.0	10.1.x	11 and later
4.0	9.0.x	8 and later

So provided you are using modern Spring Boot 3+, you need to use Tomcat 10.1+