PluggableValidator.java

/*******************************************************************************
 * Copyright (c) 1998, 2015 Oracle and/or its affiliates. All rights reserved.
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
 * which accompanies this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *     Oracle - initial API and implementation from Oracle TopLink
******************************************************************************/
package org.eclipse.persistence.tools.workbench.utility.node;

import org.eclipse.persistence.tools.workbench.utility.SynchronizedBoolean;
import org.eclipse.persistence.tools.workbench.utility.string.StringTools;


/**
 * This implementation of the Validator interface implements the
 * pause/resume portion of the protocol, but delegates the actual
 * validation to a "pluggable" delegate.
 */
public class PluggableValidator implements Node.Validator {
    private boolean pause;
    private Delegate delegate;


    /**
     * Convenience factory method.
     */
    public static Node.Validator buildAsynchronousValidator(SynchronizedBoolean validateFlag) {
        return new PluggableValidator(new AsynchronousValidator(validateFlag));
    }

    /**
     * Convenience factory method.
     */
    public static Node.Validator buildSynchronousValidator(Node node) {
        return new PluggableValidator(new SynchronousValidator(node));
    }

    /**
     * Construct a validator with the specified delegate.
     */
    public PluggableValidator(Delegate delegate) {
        super();
        this.pause = false;
        this.delegate = delegate;
    }

    /**
     * @see Node.Validator#validate()
     */
    public void validate() {
        if ( ! this.pause) {
            this.delegate.validate();
        }
    }

    /**
     * @see Node.Validator#pause()
     */
    public void pause() {
        if (this.pause) {
            throw new IllegalStateException("already paused");
        }
        this.pause = true;
    }

    /**
     * @see Node.Validator#resume()
     */
    public void resume() {
        if ( ! this.pause) {
            throw new IllegalStateException("not paused");
        }
        this.pause = false;
        // validate all the changes that occurred while the validation was paused
        this.delegate.validate();
    }

    /**
     * @see Object#toString()
     */
    public String toString() {
        return StringTools.buildToStringFor(this, this.delegate);
    }


    // ********** member interface **********

    /**
     * Interface implemented by any delegates of a pluggable validator.
     */
    public interface Delegate {

        /**
         * The validator is not "paused" - perform the appropriate validation.
         */
        void validate();


        /**
         * This delegate does nothing.
         */
        Delegate NULL_DELEGATE =
            new PluggableValidator.Delegate() {
                public void validate() {
                    // do nothing
                }
                public String toString() {
                    return "NULL_DELEGATE";
                }
            };

    }

}