title: How can I base my Spring Boot app on an external Servlet?
body: <p>I'm trying to turn <a href="https://github.com/jamesagnew/hapi-fhir/blob/master/hapi-fhir-jpaserver-examples/hapi-fhir-jpaserver-example-postgres/src/main/java/ca/uhn/fhir/jpa/demo/JpaServerDemo.java" rel="nofollow noreferrer">this example</a> into a Spring Boot application, the problem lying in that <code>RestfulServer</code> 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 <code>WebApplicationInitializer</code> and <code>SpringBootApplicationInitializer</code> is that they are not initializing the servlet before doing other <code>@Configuration</code> classes. How can I convert the <code>JpaServerDemo</code> class to Spring Boot? (note: we don't need the 2nd servlet)</p>
  
  <p><em>update</em> this is the last thing I tried, however I also tried various iterations of just <code>WebApplicationInitializer</code>, or doing things in the <code>configure</code> method which seems tricky because it has no <code>servletContext</code>, and <code>onStartup</code> has no <code>ApplicationContext</code></p>
  
  <pre><code>@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&lt;IResourceProvider&gt; 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&lt;Bundle, Meta&gt; 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&lt;IServerInterceptor&gt; 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 );
      }
  }
  </code></pre>