I agree that at first glance JavaPOS and the JCL can be rather confusing. but once you understand the concept of it, it is rather easy.  One good place to look is at  they have an open-source JavaPOS POS program that uses the JCL.  basically the idea of the JCL is to allow your POS application to open up a device, say "MyLineDisplay".  your application will then use standard UnifiedPOS calls to the line display that you opened. a simple example would be:

LineDisplay ld = new LineDisplay();"MyLineDisplay");
ld.displayText("This is a test",0);

this simple example will open up a Linedisplay object and display the text "this is a test".  where the JCL and "MyLineDisplay" comes into play is in your jpos.xml file. and Example jpos.xml file for a Ultimate Technology Linedisplay would look like this.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE JposEntries PUBLIC "=//JavaPOS//DTD//EN"
        <JposEntry logicalName="MyLineDisplay">
                <creation factoryClass="com.ultimatetechnology.jpos.UTCJposServiceInstanceFactory" serviceClass="com.ultimatetechnology.jpos.linedisplay.LineDisplayService"/>

                <vendor name="Ultimate Technology" url=""/>
                <jpos category="LineDisplay" version="1.7"/>
                <product description="JavaPOS driver for serial line display" name="PD1100" url=""/>

                <prop name="deviceBus" type="String" value="RS232"/>
                <prop name="baudRate" type="String" value="9600"/>
                <prop name="parity" type="String" value="none"/>
                <prop name="flowControl" type="String" value="none"/>
                <prop name="portName" type="String" value="COM1"/>
                <prop name="stopBits" type="String" value="1"/>
                <prop name="dataBits" type="String" value="8"/>

As you can see the jpos.xml and JCL abstract the device so that your program can just open up a LineDisplay and it won't care about any of the device settings.

I hope this helped you.

--Jeffrey Lange
Software Engineer
Ultimate Technology Corp.
(585) 742-5244

-----Original Message-----
From: Siu, Chun Kin []
Sent: Wednesday, February 05, 2003 3:11 AM
To: ''
Subject: [Jposloader-discuss] Where to start developing a JavaPOS

Hi guys,

        I am novice to retail POS system, my supervisor ask me to
investigate the difficulties in changing existing POS application to JavaPOS
competitable. For me a developer, what should I start with? I have already
download the UnifiedPOS Spec. version 1.7, but it seem not something I am
seeking for, I am now very confuse about jcl, jpos. Is there any example
that I can get a basic concept? 


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