MetadataHelper.java

/*******************************************************************************
 * Copyright (c) 2014, 2016  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:
 *     Tomas Kraus - Initial API and implementation
 ******************************************************************************/
package org.eclipse.persistence.internal.jpa.metadata.accessors;

import java.util.Collection;
import java.util.Iterator;

import org.eclipse.persistence.internal.helper.StringHelper;

/**
 * <p><b>Purpose</b>: Define any useful static methods to manipulate with descriptors content.</p>
 */
public class MetadataHelper {

    /**
     * This class is just an envelope for static methods so no instances are allowed.
     */
    private MetadataHelper() {
        throw new UnsupportedOperationException("Instances of MetadataHelper are not allowed");
    }

    /**
     * Append list of columns from descriptor class to provided {@link StringBuilder}.
     * Use to create content of columns brackets in <code>INSERT INTO table (col1, col1) VALUES ...</code>.
     * @param target Target {@link StringBuilder}.
     * @param mappings Object attributes mappings.
     * @param separator String to separate values in list.
     */
    public static void buildColsFromMappings(final StringBuilder target,
            final Collection<? extends MetadataAccessor> mappings, final String separator) {
        for (Iterator<? extends MetadataAccessor> i = mappings.iterator(); i.hasNext(); ) {
            target.append(i.next().getName().toUpperCase());
            if (i.hasNext()) {
                target.append(separator);
            }
        }
    }

    /**
     * Append list of values as list of question marks from descriptor class to provided
     * {@link StringBuilder}.
     * Use to create content of <code>VALUES</code> brackets in <code>INSERT INTO table ... VALUES (?, ?) ...</code>.
     * @param target Target {@link StringBuilder}.
     * @param mappings Object attributes mappings.
     * @param separator String to separate values in list.
     */
    public static void buildValuesAsQMarksFromMappings(final StringBuilder target,
            final Collection<? extends MetadataAccessor> mappings, final String separator) {
        final int count = mappings.size();
        if (count > 0) {
            for (int i = 0; i < count; i++) {
                if (i > 0) {
                    target.append(separator);
                }
                target.append(StringHelper.QUESTION_MARK);
            }
        }
    }

    /**
     * Append list of column to value bindings from descriptor class to provided {@link StringBuilder}.
     * Use to create value to column bindings of <code>SET</code> content in <code>UPDATE table SET col1 = ?2 WHERE ...</code>
     * @param target Target {@link StringBuilder}.
     * @param mappings Object attributes mappings.
     * @param valueIndex First value index in column to value bindings (e.g.
     *                   <code>column = ?>valueIndex></code>).
     * @param binder String to bind value to column (e.g. <code>" = "</code>
     *               in <code>column = ?>valueIndex></code>).
     * @param separator String to separate values in list.
     */
    public static void buildColsAndValuesBindingsFromMappings(final StringBuilder target,
            final Collection<? extends MetadataAccessor> mappings,
            final int valueIndex, final String binder, final String separator) {
        int idx = valueIndex;
        for (Iterator<? extends MetadataAccessor> i = mappings.iterator(); i.hasNext();) {
            target.append(i.next().getName().toUpperCase()).append(binder).append(Integer.toString(++idx));
            if (i.hasNext()) {
                target.append(separator);
            }
        }

    }

}