JWSACCMaskingClassLoader.java

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package org.glassfish.appclient.client;

import java.util.Collection;
import java.util.Collections;

/**
 * Masks classes or resources that are listed in the "endorsed" packages that
 * GlassFish provides.
 * <p>
 * During Java Web Start launches we cannot set java.endorsed.dirs to have
 * the bootstrap class loader look in the GlassFish-provided JARs for classes
 * and resources that would otherwise be found in the system JARs (rt.jar for 
 * example). We need some other way of making sure the GlassFish-provided
 * JARs are used. Those JARs are listed in the JNLP documents for the app,
 * so the JNLPClassLoader which Java Web Start provides will find them if we
 * give it a chance.
 * <p>
 * This loader knows what packages are in the GlassFish-provided endorsed JARs
 * and will report any matching class or resource as not found. When an 
 * instance of this loader is inserted as the parent of the JNLPClassLoader then
 * the JNLPClassLoader will delegate to it first.  The masking loader will
 * report GlassFish-provided content as not found, so the JNLPClassLoader will
 * try to resolve them itself.  That resolution will use the downloaded GlassFish
 * JARs, thereby making sure the Java Web Start launch uses the GlassFish-provided
 * endorsed JARs instead of whatever happens to be in the Java system JARs.
 * 
 * @author Tim Quinn
 */
class JWSACCMaskingClassLoader extends MaskingClassLoader {

    private final Collection<String> endorsedPackagesToMask;

    JWSACCMaskingClassLoader(ClassLoader parent, Collection<String> endorsedPackagesToMask) {
        super(
            parent, 
            Collections.EMPTY_SET /* punchins */, 
            Collections.EMPTY_SET /* multiples */, 
            false /* useExplicitCallsToFindSystemClass */);
        this.endorsedPackagesToMask = endorsedPackagesToMask;
    }

    @Override
    protected boolean isDottedNameLoadableByParent(final String name) {
        /*
         * Currently the only masked packages start with javax. or org.
         * Check the prefix as an optimization to avoid searching the collection.
         */
        if (!(name.startsWith("javax.") || name.startsWith("org."))) {
            return true;
        }
        
        final String packageName = name.substring(0, name.lastIndexOf("."));
        if (endorsedPackagesToMask.contains(packageName)) {
            /*
             * The requested name is one to be masked, so do not let the caller
             * delegate to its parent.
             */
            return false;
        }
        /*
         * The requested name should not be masked.  Allow the caller to delegate
         * to its parent first.
         */
        return true;
    }
}