njyjn/linkos-tomcat

Interface with LinkOS-enabled Zebra printers via your local Tomcat server

Zebra LinkOS via Tomcat

Interface with LinkOS-enabled Zebra printers via your local Tomcat server.

Background

We are attempting to connect to Zebra printers using a Tomcat server. Features at present include:

1. Query status: Query of printer status using SDK method getPrinterStatus() and supplied TCP/IP addresses.
2. Send alert to HTTP webhook Servlet POST endpoint to allow printer to send alerts using SDK method configureAlerts().
3. TODO Multithread / promise queries for the above.

1. Query status

By entering http://localhost:port/servlet/get?ip=10.10.0.1,10.10.0.2 you should be returned with a JSON object with the following information:

[
  {
    "ipAddress": "10.10.0.1",
    "hasError": true,
    "message": "Cannot Print because the printer is paused."
  },
  {
    "ipAddress": "10.10.0.2",
    "hasError": false,
    "message": "Ready To Print."
  }
]

Notes

1. The query string is parsed using delimiter ,. Thereafter each IP address string is passed into an opened Zebra connection and iterated through to obtain each print status.

2. The JSON object is built by GSON factory taking into account the object structure of ZebraPrinterStatus

public class ZebraPrinterStatus {
  private String ipAddress;
  private boolean hasError;
  private String message;
  ...
}

3. The messages can be configured according to the real statuses returned in PrinterStatusServlet.java.

if (printerStatus.isReadyToPrint) {
  message = "Ready To Print";
  hasError = false;
} else if (printerStatus.isPaused) {
  message = "Cannot Print because the printer is paused.";
} ...

2. Send alert to HTTP webhook

Opening POST endpoint in servlet method doPost() will allow it to handle incoming POST requests from the Zebra printer. Data is sent over as a HTTP multipart-form

POST /http_post/alert.php HTTP/1.1
Host: 10.3.4.58
Accept: */*
Connection: close
Content-Length: 281
Expect: 100-continue
Content-Type: multipart/form-data; boundary=------------------
----------350c75835f46
------------------------------350c75835f46
Content-Disposition: form-data; name="alertMsg"
ALERT%3A%20PRINTER%20PAUSED
------------------------------350c75835f46
Content-Disposition: form-data; name="uniqueId"
XXQLJ120900310
------------------------------350c75835f46--

This is translated into a JSON object with structure

{
  "ipAddress": "1J384DHF843",
  "hasError": true,
  "message": "ALERT: PRINTER PAUSED"
}

and sent to the webhook. The constant parameter WEBHOOK_URL in PrinterStatusServlet.java has been omitted, please furnish your own.

Notes

• Note that the IP address of the printer cannot be sent over in this iteration, since the POST request does not make this available.
• You could configure the 8th parameter in PrinterAlert to customize this message. Refer to Zebra Techdocs.

Setup

• Install the following

tomcat-8.5.23
gson-2.1

• Ensure you have opened up a GET servlet endpoint at http://localhost:8080/servlet/get and configured the necessary files. You can refer to several tutorials online to see how this is done.
• Do the same for the POST endpoint.
• Download the LinkOS SDK from Zebra, or import the file that is in lib/ZSDK_API.jar. Remember that you would need to include this file in your compile path.
• To configure printer alerts, open a servlet that uses SDK method configureAlerts(). I have implemented a simple on/off GET switch at endpoint http://localhost:8080/servlet/config.

Compilation

Use the following script or code to compile the relevant class files.

javac -classpath .:/usr/local/Cellar/tomcat/8.5.23/libexec/lib/*:/usr/local/Cellar/tomcat/8.5.23/libexec/webapps/workato/WEB-INF/lib/ZSDK_API.jar *.java

Or you could run ./compile.sh.