Spring Boot: How to add another WAR files to the embedded tomcat?

Question

Spring Boot\'s embedded tomcat is very handy, for both development and deploy.

But what if an another (3rd-party) WAR file (for example, GeoServer) should be added?<

Answer 1

You can add a war file to embedded Tomcat using Tomcat.addWebapp. As its javadoc says, it's the "equivalent to adding a web application to Tomcat's web apps directory". To use this API in Spring Boot, you need to use a custom TomcatEmbeddedServletContainerFactory subclass:

@Bean
public EmbeddedServletContainerFactory servletContainerFactory() {
    return new TomcatEmbeddedServletContainerFactory() {

        @Override
        protected TomcatEmbeddedServletContainer getTomcatEmbeddedServletContainer(
                Tomcat tomcat) {
            // Ensure that the webapps directory exists
            new File(tomcat.getServer().getCatalinaBase(), "webapps").mkdirs();

            try {
                Context context = tomcat.addWebapp("/foo", "/path/to/foo.war");
                // Allow the webapp to load classes from your fat jar
                context.setParentClassLoader(getClass().getClassLoader());
            } catch (ServletException ex) {
                throw new IllegalStateException("Failed to add webapp", ex);
            }
            return super.getTomcatEmbeddedServletContainer(tomcat);
        }

    };
}

Answer 2

It took a while to figure this out for Spring Boot 2 as none of the answers fully worked for me. I finally came up with this (fyi I have SSL turned on): WarRun.java with Gradle dependencies below to make it work.

What it gives:

embedded tomcat with context path / at https://localhost:8070

sample.war at https://localhost:8070/sample

SampleWebApp.war at https://localhost:8070/yo

import java.io.File;
import java.io.IOException;
import java.io.PrintStream;
import java.util.Properties;
import org.apache.catalina.Context;
import org.apache.catalina.startup.Tomcat;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.WebApplicationType;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory;
import org.springframework.boot.web.embedded.tomcat.TomcatWebServer;
import org.springframework.boot.web.servlet.server.ServletWebServerFactory;
import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Profile;
import org.springframework.core.io.ClassPathResource;

@ComponentScan({ "com.towianski.controllers" })
@SpringBootApplication
@Profile("server")
public class WarRun extends SpringBootServletInitializer {

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(WarRun.class).web(  WebApplicationType.SERVLET );
    }

    public static void main(String[] args) {

        SpringApplication app = new SpringApplication(WarRun.class);
        System.out.println( "Entered WarRun.main");

        String loggingFile = "";
        String dir = "";

        for ( int i = 0; i < args.length; i++ )
            {
//            logger.info( "** args [" + i + "] =" + args[i] + "=" );
            System.out.println( "** args [" + i + "] =" + args[i] + "=" );
            if ( args[i].toLowerCase().startsWith( "-dir" ) )
                {
                dir = args[i].substring( "-dir=".length() );
                }
            else if ( args[i].toLowerCase().startsWith( "--logging.file" ) )
                {
                loggingFile = args[i].substring( "--logging.file=".length() );
                stdOutFilePropertyChange( loggingFile );
                stdErrFilePropertyChange( loggingFile );
                }
            }

        Properties properties = new Properties();
//        properties.setProperty( "spring.resources.static-locations",
//                               "classpath:/home/stan/Downloads" );
        properties.setProperty( "server.port", "8070" );
//        System.setProperty("server.servlet.context-path", "/prop");     <--- Will set embedded Spring Boot Tomcat context path
        properties.setProperty( "spring.security.user.name", "stan" );
        properties.setProperty( "spring.security.user.password", "stan" );
        System.out.println( "Entered WarRun.main after set properties");
        app.setDefaultProperties(properties);
        System.out.println( "Entered WarRun.main after call set props. before app.run");

        app.run(args);
        System.out.println( "Entered WarRun.main after app.run()");
    }

    @Bean
    public ServletWebServerFactory servletContainer() {
        return new TomcatServletWebServerFactory() {
            protected TomcatWebServer getTomcatWebServer(Tomcat tomcat) {
                System.out.println( "tomcat.getServer().getCatalinaBase() =" + tomcat.getServer().getCatalinaBase() + "=" );
                new File(tomcat.getServer().getCatalinaBase(), "/webapps").mkdirs();
    //            try {
    //                Files.copy( (new File( "/home/stan/Downloads/sample.war" ) ).toPath(), (new File( tomcat.getServer().getCatalinaBase() +"/webapp/sample.war") ).toPath());
    //            } catch (IOException ex) {
    //                Logger.getLogger(WarRun.class.getName()).log(Level.SEVERE, null, ex);
    //            }
                try {
                    System.out.println( "Entered ServletWebServerFactory servletContainer()");
                    Context context2 = tomcat.addWebapp("/sample", new ClassPathResource("file:/home/stan/Downloads/sample.war").getFile().toString());
                    Context context3 = tomcat.addWebapp("/yo", new ClassPathResource("file:/home/stan/Downloads/SampleWebApp.war").getFile().toString());
    //                Context context = tomcat.addWebapp("/what", new ClassPathResource( "file:" + tomcat.getServer().getCatalinaBase() +"/webapps/sample.war" ).getFile().toString() );

                    context2.setParentClassLoader(getClass().getClassLoader());
                    context3.setParentClassLoader(getClass().getClassLoader());

    //  also works but above seems better
    //                WebappLoader loader2 = new WebappLoader(Thread.currentThread().getContextClassLoader());
    //                WebappLoader loader3 = new WebappLoader(Thread.currentThread().getContextClassLoader());
    //                context2.setLoader(loader2);
    //                context3.setLoader(loader3);
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
                return super.getTomcatWebServer(tomcat);
            }
        };
    }
}

Gradle:

apply plugin: 'war'

war {
    enabled = true
}

. . . .
dependencies {
    compile("org.springframework.boot:spring-boot-starter:2.1.6.RELEASE")
    compile("org.springframework.boot:spring-boot-starter-web:2.1.6.RELEASE") 
    compile group: 'org.apache.tomcat.embed', name: 'tomcat-embed-jasper', version: '9.0.21'
    compile("org.springframework.boot:spring-boot-starter-security:2.1.6.RELEASE")
    compile 'org.apache.httpcomponents:httpclient:4.5.7'
    compile group: 'org.codehaus.groovy', name: 'groovy-all', version: '2.5.6'
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.jcraft:jsch:0.1.55'

    testCompile group: 'junit', name: 'junit', version: '4.12'
}

Answer 3

The accepted answer covers Spring Boot 1.x. The class mentioned is no longer present in Spring Boot 2.x. When using version 2, you need to use a different one:

    @Bean
    @ConditionalOnProperty(name = "external.war.file")
    public TomcatServletWebServerFactory servletContainerFactory(@Value("${external.war.file}") String path,
                                                                 @Value("${external.war.context:}") String contextPath) {
        return new TomcatServletWebServerFactory() {

            @Override
            protected TomcatWebServer getTomcatWebServer(Tomcat tomcat) {
                new File(tomcat.getServer().getCatalinaBase(), "webapps").mkdirs();

                Context context = tomcat.addWebapp(contextPath, path);
                context.setParentClassLoader(getClass().getClassLoader());

                return super.getTomcatWebServer(tomcat);
            }

        };
    }

Also, Spring boot enbedded Tomcat does not by default contain dependencies for JSPs. If you are using JSPs in your external war, you need to include them.

<dependency>
    <groupId>org.apache.tomcat.embed</groupId>
    <artifactId>tomcat-embed-jasper</artifactId>
</dependency>
<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>jstl</artifactId>
</dependency>

UPDATE: I've written a more detailed blog post on how to set this up for both Spring Boot 1 and 2.