Controlling stdout/stderr from Jython

Question

I am calling a function in a java library from jython which prints to stdout. I would like to suppress this output from the jython script. I attempt the python idiom replacing sys.stdout with a file like object (StringIO), but this does not capture the output of the java library. I'm guessing sys.stdout does not affect the java program. Is there a standard convention for redirecting or suppressing this output programatically in jython? If not what ways can I accomplish this?

Answer 1

You can use System.setOut, like this:

>>> from java.lang import System 
>>> from java.io import PrintStream, OutputStream
>>> oldOut = System.out
>>> class NoOutputStream(OutputStream):         
...     def write(self, b, off, len): pass      
... 
>>> System.setOut(PrintStream(NoOutputStream()))
>>> System.out.println('foo')                   
>>> System.setOut(oldOut)
>>> System.out.println('foo')                   
foo

Note that this won't affect Python output, because Jython grabs System.out when it starts up so you can reassign sys.stdout as you'd expect.