CODEWITHSUNDEEP
javainternationalizationresourcebundle
Hakanai
Hakanai

Reputation: 12678

Why isn't my ResourceBundleControlProvider being loaded?

I thought I would use the new ResourceBundleControlProvider framework in Java 8 to fix something which Oracle themselves will never fix - the default encoding used when reading resource bundles.

So I made a control:

package com.acme.resources;

import java.io.IOException;
import java.util.Locale;
import java.util.ResourceBundle;

public class AcmeResourceBundleControl extends ResourceBundle.Control
{
    @Override
    public ResourceBundle newBundle(String baseName, Locale locale, String format,
                                    ClassLoader loader, boolean reload)
        throws IllegalAccessException, InstantiationException, IOException
    {
        throw new UnsupportedOperationException("TODO");
    }
}

Then I made a provider:

package com.acme.resources;

import java.util.ResourceBundle;
import java.util.spi.ResourceBundleControlProvider;

public class AcmeResourceBundleControlProvider implements ResourceBundleControlProvider
{
    private static final ResourceBundle.Control CONTROL = new AcmeResourceBundleControl();

    @Override
    public ResourceBundle.Control getControl(String baseName)
    {
        if (baseName.startsWith("com.acme."))
        {
            return CONTROL;
        }
        else
        {
            return null;
        }
    }
}

Then in META-INF/services/java.util.spi.ResourceBundleControlProvider:

com.acme.resources.AcmeResourceBundleControlProvider

Then I just tried to run our application from IDEA and I find that it never loads my provider (otherwise the exception would be raised.)

I have checked the names and they all seem to match up. I have checked the compiler output directory IDEA is using and it does contain the service file. I wrote a simple test program which just tries to look up the service:

public static void main(String[] args)
{
    for (ResourceBundleControlProvider provider :
         ServiceLoader.load(ResourceBundleControlProvider.class))
    {
        System.out.println(provider.getClass());
    }
}

This does print out one entry which is the name of my implementation class. So the issue is not in the service file.

If I breakpoint inside ResourceBundle, I seem to be able to access the custom provider class. Initial forays into the debugger show that ServiceLoader isn't finding any implementations, but I can't figure out why. I'm sure there is some dodgy class loader magic going on which results in not loading my class. :(

Some scary documentation on the Javadoc makes it sound like it might have to be installed as a global extension. If that really is the case, it's a bit of a shame, because it seemed like a useful way to override the default (and in my opinion broken) behaviour. But I also read the tutorial on the matter and it didn't seem to be describing anything like that (unless the good behaviour was pulled out of Java 8 at the very last minute and the docs are out of date!)

Upvotes: 5

Views: 988

Answers (2)

Aaron
Aaron

Reputation: 574

The tutorial does state that the JAR containing the ResourceBundleControlProvider must be in the JVM's system extension directory. Section 6 of the tutorial describes the requirement:

java -Djava.ext.dirs=lib -cp build RBCPTest

When you install a Java extension, you typically put the JAR file of the extension in the lib/ext directory of your JRE. However, this command specifies the directory that contains Java extensions with the system property java.ext.dirs.

The JavaDoc for ServiceLoader.loadInstalled() also states that providers on the application's class path are ignored.

Upvotes: 4

user3798043
user3798043

Reputation: 1

Your problem is that the java.util.ResourceBundle that comes with the JVM does a ServiceLoader.loadInstalled(ResourceBundleControlProvider.class) to obtain a list of providers in the static initializer, and uses the thus obtained list ever after.

Upvotes: 0

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