net.java.truelicense.core.ChainedLicenseConsumerManager Maven / Gradle / Ivy

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Provides license key life cycle manament.
There is a newer version: 2.6.6
/*
 * Copyright (C) 2005-2015 Schlichtherle IT Services.
 * All rights reserved. Use is subject to license terms.
 */
package net.java.truelicense.core;

import javax.annotation.concurrent.ThreadSafe;
import net.java.truelicense.core.io.*;

/**
 * A caching license consumer manager which establishes a Chain Of
 * Responsibility with its parent license consumer manager.
 * On each operation, the parent license consumer manager is tried first.
 *
 * @author Christian Schlichtherle
 */
@ThreadSafe
abstract class ChainedLicenseConsumerManager
extends CachingLicenseConsumerManager implements LicenseProvider {

    private volatile Boolean canCreateLicenseKeys;

    /** The parent license consumer manager. */
    abstract LicenseConsumerManager parent();

    private boolean canCreateLicenseKeys() {
        if (null == canCreateLicenseKeys) {
            synchronized (this) {
                if (null == canCreateLicenseKeys) {
                    try {
                        super.create(license(), new MemoryStore()); // -> /dev/null
                        canCreateLicenseKeys = true;
                    } catch (LicenseManagementException ignored) {
                        canCreateLicenseKeys = false;
                    }
                }
            }
        }
        return canCreateLicenseKeys;
    }

    @Override
    public License install(Source source) throws LicenseManagementException {
        try {
            return parent().install(source);
        } catch (final LicenseManagementException primary) {
            if (canCreateLicenseKeys()) throw primary;
            return super.install(source);
        }
    }

    @Override public License view() throws LicenseManagementException {
        try {
            return parent().view();
        } catch (final LicenseManagementException primary) {
            try {
                return super.view(); // uses store()
            } catch (final LicenseManagementException secondary) {
                synchronized (store()) {
                    try {
                        return super.view(); // repeat
                    } catch (final LicenseManagementException ternary) {
                        return createIffNewFtp(ternary); // uses store(), too
                    }
                }
            }
        }
    }

    @Override public void verify() throws LicenseManagementException {
        try {
            parent().verify();
        } catch (final LicenseManagementException primary) {
            try {
                super.verify(); // uses store()
            } catch (final LicenseManagementException secondary) {
                synchronized (store()) {
                    try {
                        super.verify(); // repeat
                    } catch (final LicenseManagementException ternary) {
                        createIffNewFtp(ternary); // uses store(), too
                    }
                }
            }
        }
    }

    @Override public void uninstall() throws LicenseManagementException {
        try {
            parent().uninstall();
        } catch (final LicenseManagementException primary) {
            if (canCreateLicenseKeys()) throw primary;
            super.uninstall();
        }
    }

    private License createIffNewFtp(final LicenseManagementException ex)
    throws LicenseManagementException {
        if (!canCreateLicenseKeys()) throw ex;
        final Store store = store();
        if (store.exists()) throw ex;
        return super.create(license(), store);
    }
}