The HAPI FHIR RestfulServer module can be used to create a FHIR server endpoint against an arbitrary data source, which could be a database of your own design, an existing clinical system, a set of files, or anything else you come up with.

HAPI also provides a persistence module which can be used to provide a complete RESTful server implementation, backed by a database of your choosing. This module uses the JPA 2.0 API to store data in a database without depending on any specific database technology.

Important Note: This implementation uses a fairly simple table design, with a single table being used to hold resource bodies (which are stored as CLOBs, optionally GZipped to save space) and a set of tables to hold search indexes, tags, history details, etc. This design is only one of many possible ways of designing a FHIR server so it is worth considering whether it is appropriate for the problem you are trying to solve.

Getting Started

The easiest way to get started with HAPI's JPA server module is to begin with the example project. There is a complete sample project found in our GitHub repo here: hapi-fhir-jpaserver-example

This example is a fully contained FHIR server, supporting all standard operations (read/create/delete/etc). It bundles an embedded instance of the Apache Derby Java database so that the server can run without depending on any external database, but it can also be configured to use an installation of Oracle, Postgres, etc.

To take this project for a spin, check out the sources from GitHib (or download a snapshot), and then build the project:

$ cd hapi-fhir-jpaserver-example
$ mvn install

You now have two options for starting the server:

  • Deploy to Tomcat/JBoss/Websphere/etc: You will now have a file in your target directory called hapi-fhir-jpaserver-example.war. This WAR file can be deployed to any Servlet container, at which point you could access the server by pointing your browser at a URL similar to the following (you may need to adjust the port depending on which port your container is configured to listen on): http://localhost:8080/hapi-fhir-jpaserver-example/
  • Run with Maven and Embedded Jetty: To start the server directly within Maven, you can execute the following command:
    $ mvn jetty:run
    You can then access the server by pointing your browser at the following URL: http://localhost:8080/hapi-fhir-jpaserver-example/

Configuring The JPA Server

The JPA server is configured through a series of configuration files, most of which are documented inline.

DaoConfig

The Spring confguration contains a definition for a bean called daoConfig, which will look something like the following:

@Bean()
public DaoConfig daoConfig() {
	DaoConfig retVal = new DaoConfig();
	retVal.setAllowMultipleDelete(true);
	retVal.setAllowInlineMatchUrlReferences(true);
	return retVal;
}

You can use this method to change various configuration settings on the DaoConfig bean which define the way that the JPA server will behave. See the DaoConfig JavaDoc for information about the available settings.

External/Absolute Resource References

Clients may sometimes post resources to your server that contain absolute resource references. For example, consider the following resource:

<Patient xmlns="http://hl7.org/fhir">
   <id value="patient-infant-01"/>
   <name>
      <use value="official"/>
      <family value="Miller"/>
      <given value="Samuel"/>
   </name>
   <managingOrganization>
      <reference value="http://example.com/fhir/Organization/123"/>
   </managingOrganization>
</Patient>

By default, the server will reject this reference, as only local references are permitted by the server. This can be changed however.

If you want the server to recognize that this URL is actually a local reference (i.e. because the server will be deployed to the base URL http://example.com/fhir/) you can configure the server to recognize this URL via the following DaoConfig setting:

@Bean()
public DaoConfig daoConfig() {
	DaoConfig retVal = new DaoConfig();
	// ... other config ...
	retVal.getTreatBaseUrlsAsLocal().add("http://example.com/fhir/");
	return retVal;
}

On the other hand, if you want the server to be configurable to allow remote references, you can set this with the confguration below. Using the setAllowInlineMatchUrlReferences means that it will be possible to search for references that refer to these external references.

@Bean()
public DaoConfig daoConfig() {
	DaoConfig retVal = new DaoConfig();
	// Allow external references
	retVal.setAllowInlineMatchUrlReferences(true);
	
	// If you are allowing external references, it is recommended to
	// also tell the server which references actually will be local
	retVal.getTreatBaseUrlsAsLocal().add("http://mydomain.com/fhir");
	return retVal;
}

Not yet complete

The documentation for the JPA server is not yet complete. Please get in touch if you are able to help us complete it!

Architecture

Architecture

The HAPI JPA Server has the following components:

  • Resource Providers: A RESTful server Resource Provider is provided for each resource type in a given release of FHIR. Each resource provider implements a @Search method implementing the complete set of search parameters defined in the FHIR specification for the given resource type.

    The resource providers also extend a superclass which implements all of the other FHIR methods, such as Read, Create, Delete, etc.

    Note that these resource providers are generated as a part of the HAPI build process, so they are not checked into Git. You can see their source in the JXR Report, for example the PatientResourceProvider.

    The resource providers do not actually implement any of the logic in searching, updating, etc. They simply receive the incoming HTTP calls (via the RestfulServer) and pass along the incoming requests to the DAOs.

  • HAPI DAOs: The DAOs actually implement all of the database business logic relating to the storage, indexing, and retrieval of FHIR resources, using the underlying JPA API.

  • Hibernate: The HAPI JPA Server uses the JPA library, implemented by Hibernate. No Hibernate specific features are used, so the library should also work with other providers (e.g. Eclipselink) but it is not tested regularly with them.

  • Database: The RESTful server uses an embedded Derby database, but can be configured to talk to any database supported by Hibernate.

Additional Information

  • This page has information on loading national editions (UK specifically) of SNOMED CT files into the database.

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