How to read several resource files with the same name from different JARs?

Question

If there are two JAR files in the classpath, both containing a resource named "config.properties" in its root. Is there a way to retrieve both files similar to getClass().getResourceAsStream()? The order is not relevant.

An alternative would be to load every property file in the class path that match certain criterias, if this is possible at all.

Sean Patrick Floyd · Accepted Answer · 2011-07-18T09:51:15.053

You need ClassLoader.getResources(name)
(or the static version ClassLoader.getSystemResources(name)).

But unfortunately there's a known issue with resources that are not inside a "directory". E.g. foo/bar.txt is fine, but bar.txt can be a problem. This is described well in the Spring Reference, although it is by no means a Spring-specific problem.

Update:

Here's a helper method that returns a list of InputStreams:

public static List<InputStream> loadResources(
        final String name, final ClassLoader classLoader) throws IOException {
    final List<InputStream> list = new ArrayList<InputStream>();
    final Enumeration<URL> systemResources = 
            (classLoader == null ? ClassLoader.getSystemClassLoader() : classLoader)
            .getResources(name);
    while (systemResources.hasMoreElements()) {
        list.add(systemResources.nextElement().openStream());
    }
    return list;
}

Usage:

List<InputStream> resources = loadResources("config.properties", classLoader);
// or:
List<InputStream> resources = loadResources("config.properties", null);

Cool. Thanks! Could you please add an example how to proceed with that URLs to get an InputStream? — Zeemee, Jul 18 '11 at 09:38
@Mulmoth: The `URL` class has an `openStream` method that returns an InputStream for that URL. That should be all you need. — Luke Woodward, Jul 18 '11 at 09:45

score 0 · Answer 2 · answered Jul 18 '11 at 09:29

0

jar files are zip files.

Open the file using java.util.zip.ZipFile

Then enumerate its entries looking for the properties file you want.

When you have the entry you can get its stream with .getInputStream()

answered Jul 18 '11 at 09:29

mbarnes

455
2
7

2

Nice idea, but I normally do not know the location and name of the jar files in code. – Zeemee Jul 18 '11 at 09:37
3

@Mulmoth yes you do: System.getProperty("java.class.path") – Sean Patrick Floyd Jul 18 '11 at 09:40
1

@Sean Patrick Floyd: Not all JAR files are on the System class path. For example in Web applications, they come from all sorts of places. – Thilo Jul 19 '11 at 00:36
@Thilo that's of course true, still, I wanted to make him aware of the method for standard situations – Sean Patrick Floyd Jul 19 '11 at 07:24

How to read several resource files with the same name from different JARs?

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