HL7

Since Camel 2.0

The HL7 component is used for working with the HL7 MLLP protocol and HL7 v2 messages using the HAPI library.

This component supports the following:

  • HL7 MLLP codec for Mina

  • HL7 MLLP codec for Netty

  • Type Converter from/to HAPI and String

  • HL7 DataFormat using the HAPI library

Maven users will need to add the following dependency to their pom.xml for this component:

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-hl7</artifactId>
    <version>x.x.x</version>
    <!-- use the same version as your Camel core version -->
</dependency>

HL7 MLLP protocol

HL7 is often used with the HL7 MLLP protocol, which is a text-based TCP socket based protocol. This component ships with a Mina and Netty Codec that conforms to the MLLP protocol, so you can easily expose an HL7 listener accepting HL7 requests over the TCP transport layer. To expose a HL7 listener service, the camel-mina or camel-netty component is used with the HL7MLLPCodec (mina) or HL7MLLPNettyDecoder/HL7MLLPNettyEncoder (Netty).

HL7 MLLP codec can be configured as follows:

Name Default Value Description

startByte

0x0b

The start byte spanning the HL7 payload.

endByte1

0x1c

The first end byte spanning the HL7 payload.

endByte2

0x0d

The 2nd end byte spanning the HL7 payload.

charset

JVM Default

The encoding (a charset name) to use for the codec. If not provided, Camel will use the JVM default Charset.

produceString

true

If true, the codec creates a string using the defined charset. If false, the codec sends a plain byte array into the route, so that the HL7 Data Format can determine the actual charset from the HL7 message content.

convertLFtoCR

false

Will convert \n to \r (0x0d, 13 decimal) as HL7 stipulates \r as segment terminators. The HAPI library requires the use of \r.

Exposing an HL7 listener using Mina

In the Spring XML file, we configure a mina endpoint to listen for HL7 requests using TCP on port 8888: 

<endpoint id="hl7MinaListener" uri="mina:tcp://localhost:8888?sync=true&amp;codec=#hl7codec"/>

sync=true indicates that this listener is synchronous and therefore will return a HL7 response to the caller. The HL7 codec is set up with codec=#hl7codec. Note that hl7codec is just a Spring bean ID, so it could be named mygreatcodecforhl7 or whatever. The codec is also set up in the Spring XML file:

<bean id="hl7codec" class="org.apache.camel.component.hl7.HL7MLLPCodec">
    <property name="charset" value="iso-8859-1"/>
</bean>

The endpoint hl7MinaLlistener can then be used in a route as a consumer, as this Java DSL example illustrates:

from("hl7MinaListener")
  .bean("patientLookupService");

This is a basic route that will listen for HL7 and route it to a service named patientLookupService. This is also Spring bean ID, configured in the Spring XML as:

<bean id="patientLookupService" class="com.mycompany.healthcare.service.PatientLookupService"/>

The business logic can be implemented in POJO classes that do not depend on Camel, as shown here:

import ca.uhn.hl7v2.HL7Exception;
import ca.uhn.hl7v2.model.Message;
import ca.uhn.hl7v2.model.v24.segment.QRD;

public class PatientLookupService {
    public Message lookupPatient(Message input) throws HL7Exception {
        QRD qrd = (QRD)input.get("QRD");
        String patientId = qrd.getWhoSubjectFilter(0).getIDNumber().getValue();

        // find patient data based on the patient id and create a HL7 model object with the response
        Message response = ... create and set response data
        return response
    }

Exposing an HL7 listener using Netty (available from Camel 2.15 onwards)

In the Spring XML file, we configure a netty endpoint to listen for HL7 requests using TCP on port 8888: 

<endpoint id="hl7NettyListener" uri="netty:tcp://localhost:8888?sync=true&amp;encoders=#hl7encoder&amp;decoders=#hl7decoder"/>

sync=true indicates that this listener is synchronous and therefore will return a HL7 response to the caller. The HL7 codec is set up with encoders=#hl7encoder*and*decoders=#hl7decoder. Note that hl7encoder and hl7decoder are just bean IDs, so they could be named differently. The beans can be set in the Spring XML file: 

<bean id="hl7decoder" class="org.apache.camel.component.hl7.HL7MLLPNettyDecoderFactory"/>
<bean id="hl7encoder" class="org.apache.camel.component.hl7.HL7MLLPNettyEncoderFactory"/>

The endpoint hl7NettyListener can then be used in a route as a consumer, as this Java DSL example illustrates:

from("hl7NettyListener")
  .bean("patientLookupService");

HL7 Model using java.lang.String or byte[]

The HL7 MLLP codec uses plain String as its data format. Camel uses its Type Converter to convert to/from strings to the HAPI HL7 model objects, but you can use the plain String objects if you prefer, for instance, if you wish to parse the data yourself.

You can also let both the Mina and Netty codecs use a plain byte[] as its data format by setting the produceString property to false. The Type Converter is also capable of converting the byte[] to/from HAPI HL7 model objects.

HL7v2 Model using HAPI

The HL7v2 model uses Java objects from the HAPI library. Using this library, you can encode and decode from the EDI format (ER7) that is mostly used with HL7v2.

The sample below is a request to look up a patient with the patient ID 0101701234.

MSH|^~\\&|MYSENDER|MYRECEIVER|MYAPPLICATION||200612211200||QRY^A19|1234|P|2.4
QRD|200612211200|R|I|GetPatient|||1^RD|0101701234|DEM||

Using the HL7 model, you can work with a ca.uhn.hl7v2.model.Message object, e.g., to retrieve a patient ID:

Message msg = exchange.getIn().getBody(Message.class);
QRD qrd = (QRD)msg.get("QRD");
String patientId = qrd.getWhoSubjectFilter(0).getIDNumber().getValue();  // 0101701234

This is powerful when combined with the HL7 listener, because you don’t have to work with byte[], String or any other simple object formats. You can just use the HAPI HL7v2 model objects. If you know the message type in advance, you can be more type-safe:

QRY_A19 msg = exchange.getIn().getBody(QRY_A19.class);
String patientId = msg.getQRD().getWhoSubjectFilter(0).getIDNumber().getValue();

HL7 DataFormat

The camel-hl7 JAR ships with a HL7 data format that can be used to marshal or unmarshal HL7 model objects.

The HL7 dataformat supports 1 options, which are listed below.

Name Default Java Type Description

validate (common)

true

Boolean

Whether to validate the HL7 message Is by default true.

  • marshal = from Message to byte stream (can be used when responding using the HL7 MLLP codec)

  • unmarshal = from byte stream to Message (can be used when receiving streamed data from the HL7 MLLP

To use the data format, simply instantiate an instance and invoke the marshal or unmarshal operation in the route builder:

  DataFormat hl7 = new HL7DataFormat();

  from("direct:hl7in")
    .marshal(hl7)
    .to("jms:queue:hl7out");

In the sample above, the HL7 is marshalled from a HAPI Message object to a byte stream and put on a JMS queue.
The next example is the opposite:

  DataFormat hl7 = new HL7DataFormat();

  from("jms:queue:hl7out")
    .unmarshal(hl7)
    .to("patientLookupService");

Here we unmarshal the byte stream into a HAPI Message object that is passed to our patient lookup service.

Segment separators

Unmarshalling does not automatically fix segment separators anymore by converting \n to \r. If you
need this conversion, org.apache.camel.component.hl7.HL7#convertLFToCR provides a handy Expression for this purpose.

Charset

Both marshal and unmarshal evaluate the charset provided in the field MSH-18. If this field is empty, by default, the charset contained in the corresponding Camel charset property/header is assumed. You can even change this default behavior by overriding the guessCharsetName method when inheriting from the HL7DataFormat class.

There is a shorthand syntax in Camel for well-known data formats that are commonly used. Then you don’t need to create an instance of the HL7DataFormat object:

  from("direct:hl7in")
    .marshal().hl7()
    .to("jms:queue:hl7out");

  from("jms:queue:hl7out")
    .unmarshal().hl7()
    .to("patientLookupService");

Message Headers

The unmarshal operation adds these fields from the MSH segment as headers on the Camel message:

Key MSH field Example

CamelHL7SendingApplication

MSH-3

MYSERVER

CamelHL7SendingFacility

MSH-4

MYSERVERAPP

CamelHL7ReceivingApplication

MSH-5

MYCLIENT

CamelHL7ReceivingFacility

MSH-6

MYCLIENTAPP

CamelHL7Timestamp

MSH-7

20071231235900

CamelHL7Security

MSH-8

null

CamelHL7MessageType

MSH-9-1

ADT

CamelHL7TriggerEvent

MSH-9-2

A01

CamelHL7MessageControl

MSH-10

1234

CamelHL7ProcessingId

MSH-11

P

CamelHL7VersionId

MSH-12

2.4

CamelHL7Context

contains the HapiContext that was used to parse the message

CamelHL7Charset

MSH-18

UNICODE UTF-8

All headers except CamelHL7Context are String types. If a header value is missing, its value is null.

Dependencies

To use HL7 in your Camel routes, you’ll need to add a dependency on camel-hl7 listed above, which implements this data format.

The HAPI library is split into a base library and several structure libraries, one for each HL7v2 message version:

By default camel-hl7 only references the HAPI base library. Applications are responsible for including structure libraries themselves. For example, if an application works with HL7v2 message versions 2.4 and 2.5, then the following dependencies must be added:

<dependency>
    <groupId>ca.uhn.hapi</groupId>
    <artifactId>hapi-structures-v24</artifactId>
    <version>2.2</version>
    <!-- use the same version as your hapi-base version -->
</dependency>
<dependency>
    <groupId>ca.uhn.hapi</groupId>
    <artifactId>hapi-structures-v25</artifactId>
    <version>2.2</version>
    <!-- use the same version as your hapi-base version -->
</dependency>

Unresolved include directive in modules/dataformats/pages/hl7-dataformat.adoc - include::spring-boot:partial$starter.adoc[]