NonOverridableHandlerFactory.java

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/*
 * @test
 * @bug 8217364
 * @summary Custom URLStreamHandler for jrt or file protocol can override default handler
 * @modules java.base/java.net:open
 * @run main/othervm NonOverridableHandlerFactory
 */

import java.io.*;
import java.net.*;

public class NonOverridableHandlerFactory implements URLStreamHandlerFactory {
    @Override
    public URLStreamHandler createURLStreamHandler(String protocol) {
        return new NonOverridableHandler();
    }

    private static class NonOverridableHandler extends URLStreamHandler {
        @Override
        protected URLConnection openConnection(URL u) throws IOException {
            throw new RuntimeException("CustomURLStreamHandler used for " + u);
        }
    }

    public static void main(String[] args) {
        URL.setURLStreamHandlerFactory(new NonOverridableHandlerFactory());
        for (String protocol : new String[] {"file", "jrt"}) {
            String urlString = protocol + ":///test/somefile";
            try {
                new URL(urlString).openConnection();
            } catch(RuntimeException r) {
                throw r;
            } catch(Throwable t) {
                // possible jrt initialization issue on exploded binary image etc.
                System.out.println("encountered: " + t +
                    "(testing: " + urlString + ")");
            }
            System.out.println("Default URLStreamHandler used for " + urlString);
        }
    }
}