run Java program with jar from Python

Question

I am trying to run a java file with a jar from Python. I first run the command :

java -classpath ".:/Users/blablalba/jackson-all-1.9.0.jar" parseJason

it worked perfectly. Then I wrote a small python script to execute the java file. (Updated: I made a change based on the suggestion below.

import os.path,subprocess
from subprocess import STDOUT,PIPE

def compile_java(java_file):
    subprocess.check_call(['javac', java_file])

def execute_java(java_file, stdin):
    java_class,ext = os.path.splitext(java_file)
   // cmd = ['java', java_class] change to
    cmd = ['java', 
  '-classpath',  '.:/Users/blablalba/jackson-all-1.9.0.jar', 
  'parseJason']
        proc = subprocess.Popen(cmd, stdin=PIPE, stdout=PIPE, stderr=STDOUT)
        stdout,stderr = proc.communicate(stdin)

compile_java('parseJason.java')
execute_java('parseJason.java', 'data.json','output_010.csv')

Data.json is the input file name and output_010.csv is the output file name. My java file gets those two parameters through reading the scanner.system.in.

Then I run the command :

    python parseJson.py

I received the following error:

import org.codehaus.jackson.map.ObjectMapper;
                                ^
parseJason.java:380: error: cannot find symbol
        ObjectMapper mapper = new ObjectMapper();
        ^
  symbol:   class ObjectMapper
  location: class parseJason
parseJason.java:380: error: cannot find symbol
        ObjectMapper mapper = new ObjectMapper();
                                  ^
  symbol:   class ObjectMapper
  location: class parseJason
3 errors
Traceback (most recent call last):
  File "parseJson.py", line 15, in <module>
    compile_java('parseJason.java')
  File "parseJson.py", line 5, in compile_java
    subprocess.check_call(['javac', java_file])
  File "/Users/***/anaconda2/lib/python2.7/subprocess.py", line 541, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['javac', 'parseJason.java']' returned non-zero exit status 1

Anyone has ideas what I am missing here? Thanks!

Thilo · Accepted Answer · 2016-11-21 08:01:26Z

2

Command '['java', 'parseJason.java']'

The command should be the same as before

the classpath is missing
the main class is called parseJason, not parseJason.java

Try

cmd = ['java', 
  '-classpath',  '.:/Users/blablalba/jackson-all-1.9.0.jar', 
  'parseJason']

edited Nov 21, 2016 at 8:01

answered Nov 21, 2016 at 7:48

Thilo

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5 Comments

user3369592 Over a year ago

Thanks for your reply. May you be more specific about how could I fix my program.Thanks again.

user3369592 Over a year ago

Thank you! I made some changed based on your suggestion and am receiving a new error.

Thilo Over a year ago

You need that classpath also for the javac command. But do you really want to compile this every time? Usually, people compile java upfront and deploy just the compiled binaries.

user3369592 Over a year ago

So you mean, I actually do not need the function "compile_java". I can compile java unfront and just run the "execute_java" function?

user3369592 Over a year ago

I upgraded to Python 3. when I run my program , I had the following error "memoryview: a bytes-like object is required, not 'str'" May you take a look at this post. Thanks stackoverflow.com/questions/40851622/…

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