Understanding how to use Interceptors

[Jordan Force]

I'm just starting out learning to use HAPI. I've cloned the JPA server starter (https://github.com/hapifhir/hapi-fhir-jpaserver-starter) repo, and switched to one of the release commits. I'm able to build and run the docker container, and visit the webpage at localhost:8080. I'm able to run the eclipse debugger and set breakpoints.

I'm trying to add authentication, and as a first step, I'm trying to set up a very simple interceptor:

@Interceptor
public class BasicSecurityInterceptor extends InterceptorAdapter{
      @Hook(Pointcut.SERVER_INCOMING_REQUEST_POST_PROCESSED)
      public boolean incomingRequestPostProcessed(RequestDetails theRequestDetails, HttpServletRequest theRequest, HttpServletResponse theResponse) {
           System.out.println("Hello");
           return true;
}
}

I placed this code into a BasicSecurityInterceptor.java file inside the ca.uhn.fhir.jpa.starter package, re-built and re-ran the docker container. I confirmed that BasicSecurityInterceptor.class is placed in the app at the expected location. Then, I set a breakpoint at the first line of incomingRequestPostProcessed, and then send a POST query to localhost:8080/fhir/Patient. I'm expecting the breakpoint to break, but it never does. What am I doing wrong? Is this the wrong procedure for hooking an interceptor to HAPI?

Thanks,

Jordan

[Kevin Dougan]

Hi Jordan,

There are a number of Interceptor examples, including downloadable source code, on this page:

https://hapifhir.io/hapi-fhir/docs/interceptors/built_in_server_interceptors.html

You can see that all of the examples call a method to register themselves:

registerInterceptor(interceptor);

It sounds like you will need to "register your Interceptor" so the server is made aware of it and knows to call it.

Hope this helps!

Kevin

[Jordan Force]

Thanks, that helps a lot! I'll give it a try.

[Dinesh Chanchalani]

Hi Kevin,

I am facing a similar issue. I did register the interceptor in a MyRestfulServer class within the initilize method.

But, what I face is pretty strange. The interceptor executes when the URL is localhost:8080/fhir/metadata but does not for localhost:8080/fhir/Patient or for  localhost:8080/fhir/Patient/mypatientId

In fact when I register the Interceptor I get a 404 response on the Patient resource GET requests but a 200 on the metadata. If I do not register the interceptor, I get a 200 response on both Patient and metadata

Here is my code (without the import statements):

package ca.uhn.fhir.jpa.starter;

@Interceptor
public class BasicSecurityInterceptor extends InterceptorAdapter {

@Hook(Pointcut.SERVER_INCOMING_REQUEST_POST_PROCESSED)
public boolean incomingRequestPostProcessed(
RequestDetails theRequestDetails, HttpServletRequest theRequest, HttpServletResponse theResponse)

throws AuthenticationException {

System.out.println("Hello");

return true;
}

}

package ca.uhn.fhir.jpa.starter;

@WebServlet(
urlPatterns = {"/fhir/*"},
displayName = "FHIR Server")
public class MyRestfulServer extends RestfulServer {

@Override
protected void initialize() throws ServletException {

System.out.println("first line in initialize");
super.initialize();

// create FhirContext for the appropriate version
setFhirContext(FhirContext.forR4());

registerInterceptor(new BasicSecurityInterceptor());

System.out.println("last line in initialize");

}
}

[Dinesh Chanchalani]

I guess I will need to register resource providers for the interceptor on work on a resource?

Added this code before the registerInterceptor line

List<IResourceProvider> resourceProviders = new ArrayList<>();
resourceProviders.add(new PatientResourceProvider());
setResourceProviders(resourceProviders);

and for a null pointer exception

2023-09-28 15:03:21.037 [http-nio-8080-exec-1] ERROR c.u.f.r.s.i.ExceptionHandlingInterceptor [ExceptionHandlingInterceptor.java:175] Failure during REST processing
ca.uhn.fhir.rest.server.exceptions.InternalErrorException: HAPI-0389: Failed to call access method: java.lang.NullPointerException: Cannot invoke "ca.uhn.fhir.jpa.api.dao.IFhirResourceDao.translateRawParameters(java.util.Map, ca.uhn.fhir.jpa.searchparam.SearchParameterMap)" because the return value of "ca.uhn.fhir.jpa.rp.r4.PatientResourceProvider.getDao()" is null
        at ca.uhn.fhir.rest.server.method.BaseMethodBinding.invokeServerMethod(BaseMethodBinding.java:269)
        at ca.uhn.fhir.rest.server.method.SearchMethodBinding.invokeServer(SearchMethodBinding.java:293)
        at ca.uhn.fhir.rest.server.method.SearchMethodBinding.invokeServer(SearchMethodBinding.java:54)
        at ca.uhn.fhir.rest.server.method.BaseResourceReturningMethodBinding.doInvokeServer(BaseResourceReturningMethodBinding.java:324)
        at ca.uhn.fhir.rest.server.method.BaseResourceReturningMethodBinding.invokeServer(BaseResourceReturningMethodBinding.java:429)
        at ca.uhn.fhir.rest.server.RestfulServer.handleRequest(RestfulServer.java:1170)
        at ca.uhn.fhir.rest.server.RestfulServer.doGet(RestfulServer.java:416)
        at ca.uhn.fhir.rest.server.RestfulServer.service(RestfulServer.java:1869)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:623)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:209)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153)
        at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:96)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153)
        at org.springframework.boot.web.servlet.support.ErrorPageFilter.doFilter(ErrorPageFilter.java:126)
        at org.springframework.boot.web.servlet.support.ErrorPageFilter.access$000(ErrorPageFilter.java:64)
        at org.springframework.boot.web.servlet.support.ErrorPageFilter$1.doFilterInternal(ErrorPageFilter.java:101)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117)
        at org.springframework.boot.web.servlet.support.ErrorPageFilter.doFilter(ErrorPageFilter.java:119)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153)
        at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:167)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:481)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:130)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93)
        at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:673)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
        at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:390)
        at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63)
        at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:926)
        at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1791)
        at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52)
        at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
        at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
        at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
        at java.base/java.lang.Thread.run(Thread.java:833)
Caused by: java.lang.reflect.InvocationTargetException: null
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.base/java.lang.reflect.Method.invoke(Method.java:568)
        at ca.uhn.fhir.rest.server.method.BaseMethodBinding.invokeServerMethod(BaseMethodBinding.java:261)
        ... 45 common frames omitted
Caused by: java.lang.NullPointerException: Cannot invoke "ca.uhn.fhir.jpa.api.dao.IFhirResourceDao.translateRawParameters(java.util.Map, ca.uhn.fhir.jpa.searchparam.SearchParameterMap)" because the return value of "ca.uhn.fhir.jpa.rp.r4.PatientResourceProvider.getDao()" is null
        at ca.uhn.fhir.jpa.rp.r4.PatientResourceProvider.search(PatientResourceProvider.java:262)