BaseJPQLQueryFormatter.java

/*******************************************************************************
 * Copyright (c) 2011, 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
 *
 ******************************************************************************/
package org.eclipse.persistence.jpa.jpql.tools.model;

import org.eclipse.persistence.jpa.jpql.Assert;
import org.eclipse.persistence.jpa.jpql.tools.model.query.StateObject;
import org.eclipse.persistence.jpa.jpql.tools.model.query.StateObjectVisitor;

/**
 * An abstract implementation of a {@link IJPQLQueryFormatter}.
 *
 * @version 2.4
 * @since 2.4
 * @author Pascal Filion
 */
@SuppressWarnings("nls")
public abstract class BaseJPQLQueryFormatter implements StateObjectVisitor,
                                                        IJPQLQueryFormatter {

    /**
     * Determines how the JPQL identifiers are written out.
     */
    protected final IdentifierStyle style;

    /**
     * The holder of the string representation of the JPQL query.
     */
    protected final StringBuilder writer;

    /**
     * The constant for a comma: ','.
     */
    protected static final String COMMA = ",";

    /**
     * The constant for a comma followed by a space: ', '.
     */
    protected static final String COMMA_SPACE = ", ";

    /**
     * The constant for the left parenthesis: '('.
     */
    protected static final String LEFT_PARENTHESIS = "(";

    /**
     * The constant for the right parenthesis: ')'.
     */
    protected static final String RIGHT_PARENTHESIS = ")";

    /**
     * The constant for a space: '  '.
     */
    protected static final String SPACE = " ";

    /**
     * Creates a new <code>BaseJPQLQueryFormatter</code>.
     *
     * @param style Determines how the JPQL identifiers are written out, which is used if the
     * {@link StateObject} was modified after its creation
     * @exception NullPointerException The {@link IdentifierStyle} cannot be <code>null</code>
     */
    protected BaseJPQLQueryFormatter(IdentifierStyle style) {

        super();

        Assert.isNotNull(style, "The IdentifierStyle cannot be null");

        this.style  = style;
        this.writer = new StringBuilder();
    }

    /**
     * Formats the given JPQL identifier, if it needs to be decorated with more information. Which
     * depends on how the string is created.
     *
     * @param identifier JPQL identifier to format
     * @return By default the given identifier is returned
     */
    protected String formatIdentifier(String identifier) {
        return style.formatIdentifier(identifier);
    }

    /**
     * Returns the style to use when formatting the JPQL identifiers.
     *
     * @return One of the possible ways to format the JPQL identifiers
     */
    public IdentifierStyle getIdentifierStyle() {
        return style;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String toString() {
        return writer.toString();
    }

    /**
     * {@inheritDoc}
     */
    public String toString(StateObject stateObject) {
        writer.delete(0, writer.length());
        stateObject.accept(this);
        return writer.toString();
    }

    /**
     * Visits the given {@link StateObject} and prevents its decorator to be called, which will
     * prevent any possible recursion when the decorator is outputting the information.
     *
     * @param stateObject The decorated {@link StateObject} to traverse without going through the
     * decorator
     */
    protected void toText(StateObject stateObject) {

        if (stateObject.isDecorated()) {

            StateObject decorator = stateObject.getDecorator();
            stateObject.decorate(null);

            try {
                decorator.accept(this);
            }
            finally {
                stateObject.decorate(decorator);
            }
        }
        else {
            stateObject.accept(this);
        }
    }
}