tools/org.eclipse.persistence.tools.gen.db/src/org/eclipse/persistence/tools/gen/db/ForeignKey.java

/*******************************************************************************
 * Copyright (c) 2008, 2012 Oracle. 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.tools.gen.db;

import java.text.Collator;
import java.util.Comparator;

/**
 * Database foreign key
 * <p>
 * Provisional API: This interface is part of an interim API that is still under development and
 * expected to change significantly before reaching stability. It is available at this early stage
 * to solicit feedback from pioneering adopters on the understanding that any code that uses this
 * API will almost certainly be broken (repeatedly) as the API evolves.
 *
 * @version 2.6
 */
@SuppressWarnings("nls")
public interface ForeignKey extends DatabaseObject {

	// ********** tables **********

	/**
	 * Returns the foreign key's <em>base</em> table.
	 */
	Table getBaseTable();

	/**
	 * Returns the foreign key's <em>referenced</em> table.
	 */
	Table getReferencedTable();


	// ********** column pairs **********

	/**
	 * Returns the foreign key's column pairs.
	 */
	Iterable<ColumnPair> getColumnPairs();

	/**
	 * Returns the size of the foreign key's column pairs.
	 */
	int getColumnPairsSize();

	/**
	 * Returns the foreign key's single column pair. Throw an
	 * {@link IllegalStateException} if the foreign key has more than one column pair.
	 */
	ColumnPair getColumnPair();

	/**
	 * Returns the foreign key's <em>base</em> columns.
	 */
	Iterable<Column> getBaseColumns();

	/**
	 * Returns the foreign key's <em>base</em> columns that are not part of the base
	 * table's primary key. (The non-primary key base columns are not used to
	 * generate basic attributes during entity generation.)
	 */
	Iterable<Column> getNonPrimaryKeyBaseColumns();

	/**
	 * Returns the foreign key's <em>referenced</em> columns.
	 */
	Iterable<Column> getReferencedColumns();

	/**
	 * Returns whether the foreign key references the primary key of the
	 * <em>referenced</em> table and that primary key has only a single column.
	 * This can be used when determining JPA defaults.
	 */
	boolean referencesSingleColumnPrimaryKey();


	// ********** JPA support **********

	/**
	 * Returns an appropriate name for an attribute that holds the entity
	 * mapped to the foreign key's <em>referenced</em> table.
	 */
	String getAttributeName();

	/**
	 * If the name of the <em>base</em> column adheres to the JPA spec for a
	 * default mapping (i.e. it ends with an underscore followed by the name
	 * of the <em>referenced</em> column, and the <em>referenced</em> column is the single
	 * Returns the corresponding
	 * default attribute name:<pre>
	 *     ForeignKey(EMP.CUBICLE_ID => CUBICLE.ID) => "CUBICLE"
	 * </pre>
	 * Returns <code>null</code> if it does not adhere to the JPA spec:<pre>
	 *     ForeignKey(EMP.CUBICLE_ID => CUBICLE.CUBICLE_ID) => null
	 *     ForeignKey(EMP.CUBICLE => CUBICLE.ID) => null
	 * </pre>
	 */
	String getDefaultAttributeName();

	/**
	 * Given the name of an attribute (field or property) that is mapped to the
	 * Returns a string to be used as the value for the
	 * attribute's <code>@javax.persistence.JoinColumn</code> annotation's
	 * Returns <code>null</code> if the attribute
	 * maps to the join column by default.
	 * <p>
	 * Precondition: The foreign key consists of a single column pair whose
	 * referenced column is the single-column primary key of the foreign
	 * key's referenced table.
	 * <p>
	 * This is used by the entity generation code to determine whether
	 * a generated annotation must explicitly identify the join column
	 * or the calculated default adequately identifies the join column
	 * (taking into consideration case-sensitivity, special characters, etc.).
	 */
	String getJoinColumnAnnotationIdentifier(String attributeName);


	// ********** column pair interface **********

	/**
	 * Pair up the foreign key's column pairs, matching each <em>base</em> column with
	 * the appropriate <em>referenced</em> column.
	 * @see #getColumnPairs()
	 */
	interface ColumnPair {

		/**
		 * Returns the column pair's <em>base</em> column.
		 */
		Column getBaseColumn();

		/**
		 * Returns the column pair's <em>referenced</em> column.
		 */
		Column getReferencedColumn();

		Comparator<ColumnPair> BASE_COLUMN_COMPARATOR =
				new Comparator<ColumnPair>() {
					@Override
					public int compare(ColumnPair cp1, ColumnPair cp2) {
						return Collator.getInstance().compare(cp1.getBaseColumn().getName(), cp2.getBaseColumn().getName());
					}
					@Override
					public String toString() {
						return "ForeignKey.ColumnPair.BASE_COLUMN_COMPARATOR";
					}
				};
	}
}