Parsing a Message |
The interface for parsing a message using any of the generation options is identical. But, before an Engine object can be used to parse a message, it's very important that the message definition file is loaded first.
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| Only one thread at a time should go through the Chameleon engine object. Multi-threaded applications should either use one engine component per thread or protect each engine using synchronization. | ||
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A good place to do this is in the Form Load event of your Visual Basic program. Care should be taken to ensure that the location of the message definition file is not hard-coded into your application:
' Notice that we use the App.Path property to ensure we load the message ' definition file that is in the same directory as the executable program. Engine.Load App.Path & "\project.vmd" |
Once the message definition file is loaded, you're ready to start parsing messages. This is done through passing an HL7 message in a string object to the Parse function of the Engine object:
Dim ResultAck As String Dim Message As String Message = "MSH|^~\&|REGADT|MCM|RSP1P8|MCM|199601051530|SEC|ADT^A44|00000007|P|2.5" + Chr(13) Message = Message + "EVN|A44|199601051530" + Chr(13) Message = Message + "PID|||MR2^^^XYZ||JONES^WILLIAM^A^JR||19501010|M|||123 EAST STREET^^NY^NY^10021||(212)111-3333|||S||ACCT1" + Chr(13) Message = Message + "MRG|MR1^^^XYZ||ACCT1" + Chr(13) ResultAck = Engine.Parse Message |
If the HL7 message can be successfully parsed, the Parse function will invoke a message event corresponding to the message type. If the parse fails, the OnParseError event will be fired instead.
As a programmer, you must provide the event code for each message defined in the message definition file. This is an example:
Private Sub Engine_OnMessagePatientUpdate(Message As HL7MsgPatientUpdate, ResultMessage As String)
On Error GoTo ErrorHandler
' The next line shows a useful diagnostic function for outputting
' the contents of a message as a formatted table string.
DisplayOutput (Message.Dump)
DisplayOutput ("Received PatientUpdate")
DisplayOutput ("With data:")
DisplayOutput ("ID: " & Message.Patient(1).ID)
DisplayOutput ("Title: " & Message.Patient(1).Title)
DisplayOutput ("GivenName: " & Message.Patient(1).GivenName)
DisplayOutput ("FamilyName: " & Message.Patient(1).FamilyName)
DisplayOutput ("Religion: " & Message.Patient(1).Religion)
DisplayOutput ("AcctNumber: " & Message.Patient(1).AcctNumber)
DisplayOutput ("DriversLicenseNo: " & Message.Patient(1).DriversLicenseNo)
DisplayOutput ("MaidenName: " & Message.Patient(1).MaidenName)
' This line shows the syntax for accessing a group.
DisplayOutput ("Insurance ID: " & Message.InsGrp(1).Guarantor(1).ID)
' The ResultMessage is a string variable which allows this code
' to return a string as a result of the Engine.Parse operation.
' Typically, this would be used to generate an ACK message to send
' back from this message.
ResultMessage = SendReturnAck
Exit Sub
ErrorHandler:
HandleError "Engine_OnMessagePatientUpdate"
End Sub
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Each of these message events has two parameters:
- A custom message object, and
- A string called ResultMessage.
The message object is a generated class that has methods for retrieving the tables that compose each message. Each table object has methods to get and set the column values in the table. These classes are described in Generated Classes.
The ResultMessage string is used to return an ACK message back to the code which invoked Engine.Parse. Whatever the event sets, the ResultMessage string will be returned as the result of the Engine.Parse function.