Issue with relative paths of resources files in an executable jar using Maven

Question

I want to make a jar file which finds similarities between task labels. For this reason I use 2 java libraries of WordNet dictionary: JWNL-1.4-rc3 and JWI-2.3.3. I also have placed, in the resources folder of myProject, the properties.xml file that is needed by JWNL library in order to be initialized, as well as the WordNet dictionary:

src/main/resources/
    properties.xml
    WordNet-3.0/dict (dict has 24 files inside)

The properties.xml file has the dictionary path with the value:

<param name="dictionary_path" value="WordNet-3.0\dict"/>

In my code, I have the two code snippets shown below.

This code initializes the JWNL library:

try {
    JWNL.initialize(similarities.class.getClassLoader().getResourceAsStream("/properties.xml"));
}
catch (JWNLException e) {
    e.printStackTrace();
}

similarities is my main class.

This is the constructor of the JWI dictionary:

try {
    //String path = similarities.class.getProtectionDomain().getCodeSource().getLocation().getPath();
    dict=new Dictionary(this.getClass().getClassLoader().getResource("WordNet-3.0\\dict"));
    dict.open();
} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

But when I export an executable jar and run it in the console, I get the following error:

net.didion.jwnl.JWNLException: Properties file invalid or not found
at net.didion.jwnl.JWNL.initialize(JWNL.java:103)
at com.iteforth.annotationToBPM.similarities.main(similarities.java:576)
Exception in thread "main" java.lang.NullPointerException
at edu.mit.jwi.data.FileProvider.<init>(FileProvider.java:191)
at edu.mit.jwi.data.FileProvider.<init>(FileProvider.java:166)
at edu.mit.jwi.data.FileProvider.<init>(FileProvider.java:148)
at edu.mit.jwi.Dictionary.<init>(Dictionary.java:41)
at com.iteforth.annotationToBPM.similarities.<init>(similarities.java:92)
at com.iteforth.annotationToBPM.similarities.main(similarities.java:627)

I have already opened my jar file and I have checked that there is a resources folder inside with the properties.xml and the WordNet dictionary. I also have opened MANIFEST and I have seen that the class path is: . (full stop)

I have read many threads about this issue for 3 days but nothing has solved my problem. I will appreciate any help.

Tell me if I must send something else, e.g., the POM.xml or properties.xml files.

You must _always_ check for null when looking up a resource! — Thorbjørn Ravn Andersen, Mar 23 '16 at 10:04

score 1 · Accepted Answer · edited May 23 '17 at 10:29

1

The error you have is related to the loading of the properties file, but I think you will get an other one with the dictionnary loading.

For the properties file:

JWNL.initialize(ClassLoader.getSystemResourceAsStream("properties.xml"));

Be sure that your file is located at the root of your jar. That should be the case if your source file is in src/main/resources as it is the default maven configuration. If your properties file is in a "resources" folder in your jar as you said, this become :

JWNL.initialize(ClassLoader.getSystemResourceAsStream("resources/properties.xml"));

For the dictionnary: The API is not designed to read dictionnary files inside the jar. In edu.mit.jwi.data.FileProvider at line 363, you would see:

File directory = toFile(url);
    if (!directory.exists()) 
        throw new IOException("Dictionary directory does not exist: " + directory);

so you have to keep them outside your jar, in the filesystem :

dict = new Dictionary(new File("WordNet-3.0\\dict"));
dict.open();

Note: Of course, putting a hard coded absolute path in your code would be a bad idea.

You could put the dictionnary directory in the same directory as your jar, if your jar is always run from this directory, and access it with a relative file path in your code as above (see How does Java resolve a relative path in new File()?)

Or you could let the user configure the directory path with a command line arguments (https://docs.oracle.com/javase/tutorial/essential/environment/cmdLineArgs.html) or an environnement variable (https://docs.oracle.com/javase/tutorial/essential/environment/env.html)

Example with an environnement variable:

user define an environnement variable, for exemple :
```
set WORD_NET_DICTIONARY = "C:\WordNet-3.0\Dict"
```

you can get this env variable in your code and configure your library:

String wordNetDicDir = System.getenv("WORD_NET_DICTIONARY");
if (wordNetDicDir != null) {
   dict = new Dictionary(new File(wordNetDicDir));
   dict.open();
} else {
   // throw exception or log error
   ...
}

edited May 23 '17 at 10:29

Community

1
1

answered Mar 23 '16 at 10:43

Hugo G.

636
6
21

Thank you Hugo G. You solved my issue in 20 minutes and i had searched for it for 3 days!!! Could i ask something else too? I placed WordNet dictionary in C:/WordNet-3.0/dict directory. I want to import this jar file in a platform and run in anyone machine. I must create a readme txt which warns for placing WordNet dictionary in C: directory? – joan Mar 23 '16 at 11:16
That would be a bad idea : what if your user don't have a C letter drive or if he is on linux or mac ? I updated my answer with some ways to do that. – Hugo G. Mar 23 '16 at 11:45
I think that the better solution for my case is to use environment variable but i don't know how and i didn't understand the above link. I use a CLASSPATH variable with value: . (dot)(current working directory) and place it in the dictionary-path in properties.xml file: and in the dictionary constructor in java: dict = new Dictionary(new File("${CLASSPATH}WordNet-3.0\\dict")); But i have the following errors: The properties file must specify a dictionary path and Dictionary directory doesn't exits. Any idea how to use it? – joan Mar 23 '16 at 16:56
`CLASSPATH` does not denote a directory, it is a list of files and directories included in the java classpath. I added an example that uses a environnement variable to configure the location of the dictionnary. Please consider accepting the answer if it helped you. – Hugo G. Mar 29 '16 at 08:42
Sorry for the delay....the above example doesn't work because of the constructor of dictionary. It gets only URL or file and the wordNetDicDir is a String....Do you have any solution about this? Thanks in advance!!! – joan Apr 06 '16 at 08:59
File has a constructor that takes a String parameter as the path of the file. – Hugo G. Apr 06 '16 at 10:23
Thank you so much Hugo G.!!!! Something last... I also use a property.xml file for the JWNL library which contains the WordNet dictionary path with the value: '' How could i make dictionary_path in properties file independent of letter C driver to be used in any machine? – joan Apr 07 '16 at 08:27

Issue with relative paths of resources files in an executable jar using Maven

1 Answers1