Simplify using an interceptor with Docker

Now it is possible to mount a folder with extra classes that are loaded
by HAPI. This makes it easy to load an interceptor JAR while using the
standard Docker image. The README explains how to use it.

Spring by default uses the WarLauncher. Now the ENTRYPOINT uses the
PropertiesLauncher, configured in such a way that it is compatible with
the WarLauncher, but adding the folder /app/extra-classes to the
loader.path.

Dockerfile

@@ -46,4 +46,4 @@ WORKDIR /app
 COPY --chown=nonroot:nonroot --from=build-distroless /app /app
 COPY --chown=nonroot:nonroot --from=build-hapi /tmp/hapi-fhir-jpaserver-starter/opentelemetry-javaagent.jar /app
 
-CMD ["/app/main.war"]
+ENTRYPOINT ["java", "--class-path", "/app/main.war", "-Dloader.path=main.war!/WEB-INF/classes/,main.war!/WEB-INF/,/app/extra-classes", "org.springframework.boot.loader.PropertiesLauncher", "app/main.war"]

README.md

@@ -75,6 +75,7 @@ services:
     depends_on:
       - db
 
+
   db:
     image: postgres
     restart: always
@@ -105,6 +106,87 @@ spring:
       hibernate.search.enabled: false
 ```
 
+### Example running custom interceptor using docker-compose
+
+This example is an extension of the above one, now adding a custom interceptor.
+
+```yaml
+version: '3.7'
+
+services:
+  fhir:
+    container_name: fhir
+    image: "hapiproject/hapi:latest"
+    ports:
+      - "8080:8080"
+    configs:
+      - source: hapi
+        target: /app/config/application.yaml
+      - source: hapi-extra-classes
+        target: /app/extra-classes
+    depends_on:
+      - db
+
+  db:
+    image: postgres
+    restart: always
+    environment:
+      POSTGRES_PASSWORD: admin
+      POSTGRES_USER: admin
+      POSTGRES_DB: hapi
+    volumes:
+      - ./hapi.postgress.data:/var/lib/postgresql/data
+
+configs:
+  hapi:
+     file: ./hapi.application.yaml
+  hapi-extra-classes:
+     file: ./hapi-extra-classes
+```
+
+Provide the following content in ``./hapi.aplication.yaml``:
+
+```yaml
+spring:
+  datasource:
+    url: 'jdbc:postgresql://db:5432/hapi'
+    username: admin
+    password: admin
+    driverClassName: org.postgresql.Driver
+  jpa:
+    properties:
+      hibernate.dialect: ca.uhn.fhir.jpa.model.dialect.HapiFhirPostgres94Dialect
+      hibernate.search.enabled: false
+hapi:
+  fhir:
+    custom-bean-packages: the.package.containing.your.interceptor
+    custom-interceptor-classes: the.package.containing.your.interceptor.YourInterceptor
+```
+
+The basic interceptor structure would be like this:
+
+```java
+package the.package.containing.your.interceptor;
+
+import org.hl7.fhir.instance.model.api.IBaseResource;
+import org.springframework.stereotype.Component;
+
+import ca.uhn.fhir.interceptor.api.Hook;
+import ca.uhn.fhir.interceptor.api.Interceptor;
+import ca.uhn.fhir.interceptor.api.Pointcut;
+
+@Component
+@Interceptor
+public class YourInterceptor
+{
+    @Hook(Pointcut.STORAGE_PRECOMMIT_RESOURCE_CREATED)
+    public void resourceCreated(IBaseResource newResource)
+    {
+        System.out.println("YourInterceptor.resourceCreated");
+    }
+}
+```
+
 ## Running locally
 
 The easiest way to run this server entirely depends on your environment requirements. At least, the following 4 ways are supported: