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HL7V2 HAPI parser exception while receiving data via TCP/IP

I'm using the HAPI hapi-structures-v25 library with version 2.3 to parse HL7v2 message & convert that into FHIR resources. I'm facing a strange issue while receiving and parsing the HL7V2 message using HAPI via TCP listener.

Determine encoding for message. The following is the first 50 chars of the message for reference, although this may not be where the issue is: MSH|^~\&|test|DrJhonDoe|TEST|UNKNOWN|20210216190432||ADT^A01^ADT_A01|60b647d4-b5a5-4fae-a928-d4a3849de3c8|T|2.5

Strange that I'm not getting this error when I'm trying to send this message as a string in main function. I'm getting this error only when I receive the data over TCP/IP to my Java function. I tried sending the HL7 message to my receiving TCP port using Mirth as well external tool & my result is same.

Here is the sample of my HL7v2 message Im trying to process

MSH|^~\\&|test|Dr.JhonDoe|TEST|UNKNOWN|20210216190432.7||ADT^A01^ADT_A01|60b647d4b5a54faea928d4a3849de3c8|T|2.5
EVN||20210216|20210216|

While receiving the data from tcp/ip im converting the byte to string using the UTF-8 charset.

InputStream in = connection.getInputStream();
OutputStream out = connection.getOutputStream();
receivedMessageSize = in.read(receivedByeBuffer);
String incomingHl7Message = new String(receivedByeBuffer, StandardCharsets.UTF_8);

Im getting the message properly. But not sure why the error comes.

Solution

  • As mentioned in the answer by Amit, it needs to be escaped in JAVA. The HL7v2 when transmitted via MLLP it adds <VT>, <CR> Unicode data to the text. The understanding needed here is that these are not junk characters. By the protocol of MLLP the starting and ending of the messages are marked by these unicode characters to describe the starting and ending of a frame.

    The HAPI HL7 parse cannot parse these special (non-printable) characters. Happy that I've found a solution on the same forum to handle it in java wisely. How to remove control characters from java string?

    A simple regex will do the trick as shown below:

    .replaceAll("[\\p{Cntrl}&&[^\r\n\t]]", "");

    Also make sure that you're encoding characters are also handled properly with JAVA. Usually JAVA is not good in handling backslash. So, escape the backslash .replace("\\", "\\\\")

    This will do the trick.