How can I base my Spring Boot app on an external Servlet?

Question

I'm trying to turn this example into a Spring Boot application, the problem lying in that RestfulServer is a servlet, and I"m not really trying to make a separate app, but a single one that, more or less extends that servlet. Problem I seem to be running into though is that things I've tried with WebApplicationInitializer and SpringBootApplicationInitializer is that they are not initializing the servlet before doing other @Configuration classes. How can I convert the JpaServerDemo class to Spring Boot? (note: we don't need the 2nd servlet)

update this is the last thing I tried, however I also tried various iterations of just WebApplicationInitializer, or doing things in the configure method which seems tricky because it has no servletContext, and onStartup has no ApplicationContext

@SpringBootApplication
public class Application extends SpringBootServletInitializer {


    @Override
    public void onStartup( ServletContext servletContext ) throws ServletException {
        super.onStartup( servletContext );

        RestfulServer server = new RestfulServer();
        servletContext.addServlet( "restful", server );
            /*
         * We want to support FHIR DSTU3 format. This means that the server
         * will use the DSTU3 bundle format and other DSTU3 encoding changes.
         *
         * If you want to use DSTU1 instead, change the following line, and change the 3 occurrences of dstu2 in web.xml to dstu1
         */
        server.setFhirContext( FhirContext.forDstu3() );
        WebApplicationContext myAppCtx = this.createRootApplicationContext( servletContext );

        // Get the spring context from the web container (it's declared in web.xml)

    /*
     * The BaseJavaConfigDstu3.java class is a spring configuration
     * file which is automatically generated as a part of hapi-fhir-jpaserver-base and
     * contains bean definitions for a resource provider for each resource type
     */
        List<IResourceProvider> beans = myAppCtx.getBean( "myResourceProvidersDstu3", List.class );
        server.setResourceProviders( beans );

        /*
         * The system provider implements non-resource-type methods, such as
         * transaction, and global history.
         */
        server.setPlainProviders( myAppCtx.getBean( "mySystemProviderDstu3", JpaSystemProviderDstu3.class ) );

    /*
     * The conformance provider exports the supported resources, search parameters, etc for
     * this server. The JPA version adds resource counts to the exported statement, so it
     * is a nice addition.
     */
        IFhirSystemDao<Bundle, Meta> systemDao = myAppCtx.getBean( "mySystemDaoDstu3", IFhirSystemDao.class );
        DaoConfig daoConfig = myAppCtx.getBean( DaoConfig.class );
        JpaConformanceProviderDstu3 confProvider = new JpaConformanceProviderDstu3( server, systemDao, daoConfig );
        confProvider.setImplementationDescription( "Example Server" );
        server.setServerConformanceProvider( confProvider );

        /*
         * Enable ETag Support (this is already the default)
         */
        server.setETagSupport( ETagSupportEnum.ENABLED );

    /*
     * This server tries to dynamically generate narratives
     */
        FhirContext ctx = server.getFhirContext();
        ctx.setNarrativeGenerator( new

                DefaultThymeleafNarrativeGenerator() );

        /*
         * Default to JSON and pretty printing
         */
        server.setDefaultPrettyPrint( true );
        server.setDefaultResponseEncoding( EncodingEnum.JSON );

        /*
         * -- New in HAPI FHIR 1.5 --
         * This configures the server to page search results to and from
         * the database, instead of only paging them to memory. This may mean
         * a performance hit when performing searches that return lots of results,
         * but makes the server much more scalable.
         */
        server.setPagingProvider( myAppCtx.getBean( DatabaseBackedPagingProvider.class ) );

    /*
     * Load interceptors for the server from Spring (these are defined in FhirServerConfig.java)
     */
        Collection<IServerInterceptor> interceptorBeans = myAppCtx.getBeansOfType( IServerInterceptor.class ).values();
        for (
                IServerInterceptor interceptor : interceptorBeans )

        {
            server.registerInterceptor( interceptor );
        }

        /*
         * If you are hosting this server at a specific DNS name, the server will try to
         * figure out the FHIR base URL based on what the web container tells it, but
         * this doesn't always work. If you are setting links in your search bundles that
         * just refer to "localhost", you might want to use a server address strategy:
         */
        //setServerAddressStrategy(new HardcodedServerAddressStrategy("http://example.com/fhir/baseDstu2"));

        /*
         * If you are using DSTU3+, you may want to add a terminology uploader, which allows
         * uploading of external terminologies such as Snomed CT. Note that this uploader
         * does not have any security attached (any anonymous user may use it by default)
         * so it is a potential security vulnerability. Consider using an AuthorizationInterceptor
         * with this feature.
         */
        server.registerProvider( myAppCtx.getBean( TerminologyUploaderProviderDstu3.class ) );


    }

    @Override
    protected SpringApplicationBuilder configure( final SpringApplicationBuilder builder ) {
        return builder;
    }

    public static void main( String[] args ) {
        configureApplication( new SpringApplicationBuilder() ).run( args );
    }

    private static SpringApplicationBuilder configureApplication( final SpringApplicationBuilder builder ) {
        return builder.sources( Application.class );
    }
}

Answer 1

This seems to work, I added @WebServlet to the class, and injected the WebApplicationContext using Spring 4.3's annotationless constructor injection feature. I also added @ServletComponentScan to my Application which is in the same package

@WebServlet( "/fhir/*" )
public class FhirServlet extends RestfulServer {

    private static final long serialVersionUID = 3341258540126825379L;
    private final WebApplicationContext myAppCtx;

    public FhirServlet( WebApplicationContext myAppCtx ) {
        this.myAppCtx = myAppCtx;
    }

    @Override
    protected void initialize() throws ServletException {
        this.setFhirContext( FhirContext.forDstu3() );
        this.setServerAddressStrategy( new IncomingRequestAddressStrategy() );
        this.setDefaultPrettyPrint( true );
        this.setDefaultResponseEncoding( EncodingEnum.JSON );
        this.setETagSupport( ETagSupportEnum.ENABLED );

        /*
         * The BaseJavaConfigDstu3.java class is a spring configuration
         * file which is automatically generated as a part of hapi-fhir-jpaserver-base and
         * contains bean definitions for a resource provider for each resource type
         */
        List<IResourceProvider> beans = myAppCtx.getBean( "myResourceProvidersDstu3", List.class );
        setResourceProviders( beans );

        /*
         * The system provider implements non-resource-type methods, such as
         * transaction, and global history.
         */
        setPlainProviders( myAppCtx.getBean( "mySystemProviderDstu3", JpaSystemProviderDstu3.class ) );

        /*
         * The conformance provider exports the supported resources, search parameters, etc for
         * this server. The JPA version adds resource counts to the exported statement, so it
         * is a nice addition.
         */
        IFhirSystemDao<Bundle, Meta> systemDao = myAppCtx.getBean( "mySystemDaoDstu3", IFhirSystemDao.class );
        JpaConformanceProviderDstu3 confProvider = new JpaConformanceProviderDstu3( this, systemDao, myAppCtx.getBean( DaoConfig.class ) );
        confProvider.setImplementationDescription( "Example Server" );
        setServerConformanceProvider( confProvider );

        /*
         * This server tries to dynamically generate narratives
         */
        getFhirContext().setNarrativeGenerator( new DefaultThymeleafNarrativeGenerator() );

        /*
         * -- New in HAPI FHIR 1.5 --
         * This configures the server to page search results to and from
         * the database, instead of only paging them to memory. This may mean
         * a performance hit when performing searches that return lots of results,
         * but makes the server much more scalable.
         */
        setPagingProvider( myAppCtx.getBean( DatabaseBackedPagingProvider.class ) );

        /*
         * Load interceptors for the server from Spring (these are defined in FhirServerConfig.java)
         */
        Collection<IServerInterceptor> interceptorBeans = myAppCtx.getBeansOfType( IServerInterceptor.class ).values();
        for ( IServerInterceptor interceptor : interceptorBeans ) {
            this.registerInterceptor( interceptor );
        }

        /*
         * If you are hosting this server at a specific DNS name, the server will try to
         * figure out the FHIR base URL based on what the web container tells it, but
         * this doesn't always work. If you are setting links in your search bundles that
         * just refer to "localhost", you might want to use a server address strategy:
         */
        //setServerAddressStrategy(new HardcodedServerAddressStrategy("http://example.com/fhir/baseDstu2"));

        /*
         * If you are using DSTU3+, you may want to add a terminology uploader, which allows
         * uploading of external terminologies such as Snomed CT. Note that this uploader
         * does not have any security attached (any anonymous user may use it by default)
         * so it is a potential security vulnerability. Consider using an AuthorizationInterceptor
         * with this feature.
         */
        registerProvider( myAppCtx.getBean( TerminologyUploaderProviderDstu3.class ) );
    }
}