How do I access a config file inside the jar?

Question

I'm using FlatPack to parse and load data from flat files. This requires loading a config file that stores mappings of the columns of the flat file.

I have a constant to define the location of the mapping file:

private static final String MAPPING_FILE = "src/com/company/config/Maping.pzmap.xml";

I have a parse(File dataFile) method that actually does the parsing:

private void parse(File dataFile) throws FileNotFoundException, SQLException {
        Parser parser;

        log.info("Parsing " + dataFile.getName());

        FileReader mappingFileReader = new FileReader(MAPPING_FILE);
        FileReader dataFileReader = new FileReader(dataFile);

        parser = DefaultParserFactory.getInstance().newFixedLengthParser(mappingFileReader, dataFileReader);
        parser.setHandlingShortLines(true);

        DataSet dataSet = parser.parse();

        //process the data
}

When I jar up everything and run it as a jar - it bombs out on FileReader mappingFileReader = new FileReader(MAPPING_FILE); with a FileNotFoundException. That file is inside the jar though.

How do I get to it?

I've looked at this question and this question about accessing files inside jars and they both recommend temporarily extracting the file. I don't want to do that though.

Answer 1

if it's inside a JAR, it's not a File, generally speaking. You should load the data using Class.getResourceAsStream(String), or something similar.

Answer 2

I think it is solved just here:

http://www.velocityreviews.com/forums/t129474-beginner-question-how-to-access-an-xml-file-inside-a-jar-without-extracting-it.html

Answer 3

If I remember correctly, getResourceAsStream() can behave differently depending on which web server your webapp is deployed, for instance I think it can be a problem when deployed as a war on a Websphere instance. But I'm not sure if this applies to you.

But I'm not sure you're trying to solve the "proper" problem : if it's a config file, that means is data dependant right ? Not code dependant ( your jar ) ? When the flat file will change, your config file will need to change as well, right ? If this is true, it sounds like the config should be better stored elsewhere, or even passed as a parameter to your jar.

But maybe I haven't fully understood your problem...

Answer 4

Use Apache Commons Configuration, then you can read/write XML, auto update, find config file in path or jar, without a lot of hassles.

Answer 5

Just unzip jar, so you can access directory structure.