How to invoke a java program with classpath from Python 3.x

Question

I am trying to execute an external java program from a python 3.7 program using the java command with classpath. I am using subprocess.Popen module in Python. Somehow I am not able to get it working! Appreciate any assistance!

cmd = ['java',
           '-classpath', 'C:/Users/Documents/MqTransfer.jar', 'C:/Users/Documents/com.ibm.mq.commonservices.jar',
           'C:/Users/Documents/com.ibm.mq.headers.jar', 'C:/Users/Documents/com.ibm.mq.jar',
           'C:/Users/Documents/com.ibm.mq.jmqi.jar', 'C:/Users/Documents/com.ibm.mq.pcf.jar',
           'C:/Users/Documents/connector.jar', 'C:/Users/Documents/xerces.jar',
           'MyMqTransfer', 'C:/Users/Documents/queueTransfer.properties']
    jproc = subprocess.Popen(cmd, stdout=PIPE, stderr=PIPE)
    output, errors = jproc.communicate()
    print(output, errors)

I am getting the below error

b'' b'Error: Could not find or load main class C:.Users.Documents.com.ibm.mq.commonservices.jar\r\n'

When I try to run the java program from my batch script it runs fine! This is the command I use in my batch script. The issue is with my python code!

java -classpath MqTransfer.jar;com.ibm.mq.commonservices.jar;com.ibm.mq.headers.jar;com.ibm.mq.jar;com.ibm.mq.jmqi.jar;com.ibm.mq.pcf.jar;connector.jar;xerces.jar  com.ibm.my.mq.MyMqTransfer C:\Users\Documents\queueTransfer.properties

I can run the java program perfect from a batch program I use but when I try to invoke from my python program it fails! — sijo0703, Jun 03 '19 at 20:21
Oh it's a Python specific question then. Sorry that I can't help you in there I am a Java dev. — Matthew, Jun 03 '19 at 20:22

NinePlanFailed · Accepted Answer · 2019-06-03T20:36:34.360

Based on the error, I believe the process being executed is something like 'java -classpath C:/Users/Documents/MqTransfer.jar c:/Users/Documents/com.ibm.mq.commonServices.jar [followed by the rest of the arguments you are passing to process]' such that java is passed MqTransfer.jar as the entire classpath argument and thinks 'C:.Users.Documents.com.ibm.mq.commonservices.jar' is your class to launch. Try combining your entire intended classpath into the 3rd argument of your launch and I think you will be good. It would look something like this:

cmd = ['java',
           '-classpath', 'C:/Users/Documents/MqTransfer.jar;C:/Users/Documents/com.ibm.mq.commonservices.jar;C:/Users/Documents/com.ibm.mq.headers.jar;C:/Users/Documents/com.ibm.mq.jar;C:/Users/Documents/com.ibm.mq.jmqi.jar;C:/Users/Documents/com.ibm.mq.pcf.jar;C:/Users/Documents/connector.jar;C:/Users/Documents/xerces.jar',
           'MyMqTransfer', 'C:/Users/Documents/queueTransfer.properties']

How to invoke a java program with classpath from Python 3.x

1 Answers1