Exception in thread "main" java.lang.NoClassDefFoundError: org/slf4j/LoggerFactory
at edu.stanford.nlp.parser.common.ParserGrammar.
Caused by: java.lang.ClassNotFoundException: org.slf4j.LoggerFactory
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 1 more
Traceback (most recent call last):
File "test_stanford.py", line 23, in
sentences = dp.parse_sents(("Hello, My name is Evelin.", "What is your name?"))
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/nltk/parse/stanford.py", line 129, in parse_sents
cmd, '\n'.join(' '.join(sentence) for sentence in sentences), verbose))
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/nltk/parse/stanford.py", line 225, in _execute
stdout=PIPE, stderr=PIPE)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/nltk/internals.py", line 135, in java
raise OSError('Java command failed : ' + str(cmd))
OSError: Java command failed :...
So, I investigated this issue in so many Stackoverflow posts, NLTK documentation, and StanfordParser documentation. Nevertheless, most of information I collected was about earlier version of NLTK and Stanford earlier versions. After some debugging, I found out that one important file wasn't in Java command of NLTK library. This file is slf4j-api.jar.
Now, let's start from the beginning. First let's see how is code for use StanfordParser with NLTK. you'll need the following imports in your code:
from nltk.parse.stanford import StanfordDependencyParser
import os
os library is to set environment variables STANFORD_PARSER and CLASSPATH. You can do this like in the following code lines:
os.environ['STANFORD_PARSER'] = '/path/to/your/stanford-parser/unzip/directory'
os.environ['CLASSPATH'] = '/path/to/your/stanford-parser/unzip/directory/'
After that you can instantiate a StanfordDependencyParser like that:
dp = StanfordDependencyParser(model_path='/path/to/your/englishPCFG.ser.gz')
File englishPCFG.ser.gz is inside stanford-parser-3.6.0-models.jar, so you can extract your model file from this jar.
Finally, you are able to parse your sentences using the next line of code.
sentences = dp.parse_sents(("Hello, My name is Evelin.", "What is your name?"))
Then, I got the error that I pasted in the beginning os this post. So, what did I do? I debugged the following two files of the NLTK API: /Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/nltk/internals.py and /Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/nltk/parse/stanford.py. I saw that the java command built by NLTK API consider in classpath only stanford-parser-3.6.0-models.jar and stanford-parser.jar, but we also need slf4j-api.jar to execute StanfordParser. I tried to set CLASSPATH, but that didn't work for me, so I actually changed stanford.py code. I added the following lines to code:
_MAIN_JAR = r'slf4j-api\.jar' # right after _JAR variable set up
# this code goes right before line: self._classpath = (stanford_jar, model_jar)
main_jar=max(
find_jar_iter(
self._MAIN_JAR, path_to_models_jar,
env_vars=('STANFORD_MODELS', 'STANFORD_CORENLP'),
searchpath=(), url=_stanford_url,
verbose=verbose, is_regex=True
),
key=lambda model_name: re.match(self._MAIN_JAR, model_name)
)
# and I changed ...
self._classpath = (stanford_jar, model_jar)
#to...
self._classpath = (stanford_jar, model_jar, main_jar)
I know that it is not a elegant solution, but it worked fine, so for now I think I will use it. Any suggestions are welcomed.
