Question

I m trying to use HAPI to parse HL7 (v2.3) messages generated by an external system. These messages include custom Z segments, including the second segment of the message (between MSH and EVN).

MSH
Z
EVN
...

The problem is that for any segments parsed after encountering this first Z segment, HAPI will generate the message structure but all data in that structure is null. So, I ll still have an EVN segment object, but it won t have any data in it.

I ve tried:

Nothing, just parse the message with out-of-the-box HAPI, and ignore this segment
Extending HAPI by creating my own ADT message classes (extending the default classes) connecting in the Z segment with:
- addNonstandardSegment()
- add() with a custom implementation of AbstractSegment

My current workaround is to pre-parse the message before HAPI gets it and cut out this segment, but this is definitely the wrong approach. Does anyone have ideas on what I should be doing?

Answer 1

Got it. It turns out that, because of the out-of-place Z-segment (more on this below), the EVN object was being cataloged internally as "EVN2" and a second blank EVN was being added in. I m not quite sure why the code behaved this way, but I ll take that up in an issue report in the HAPI project.

The workaround is to alter the extension of the ADT message. Instead of extending it and adding the Z-segment with this.add() in my subclass constructor, I had to copy the original ADT_A* class and modify its init() method to add the Z segment class in the proper order as the expected message.

BTW, the previous workaround I mentioned can be done with a subclassed parser, which is valid for fixing broken messages - just not this one, since it isn t "broken" per se.

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