JDBCExternalForeignKeyColumnPair.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.mappingsmodel.spi.db.jdbc;

import java.sql.ResultSet;
import java.sql.SQLException;

import org.eclipse.persistence.tools.workbench.mappingsmodel.spi.db.ExternalColumn;
import org.eclipse.persistence.tools.workbench.mappingsmodel.spi.db.ExternalForeignKeyColumnPair;
import org.eclipse.persistence.tools.workbench.utility.string.StringTools;


/**
 * Associate a pair of columns from a foreign key that is made
 * up of, possibly, multiple pairs of columns.
 * Either column can be null if we have any problems gathering
 * up the meta-data.
 */
final class JDBCExternalForeignKeyColumnPair implements ExternalForeignKeyColumnPair {
    private final JDBCExternalForeignKey foreignKey;
    private final ExternalColumn sourceColumn;
    private final ExternalColumn targetColumn;


    // ********** constructor/initialization **********

    /**
     *
     * @see java.sql.DatabaseMetaData#getImportedKeys(String, String, String)
     */
    JDBCExternalForeignKeyColumnPair(JDBCExternalForeignKey foreignKey, ResultSet resultSet) {
        super();
        this.foreignKey = foreignKey;
        this.sourceColumn = this.columnNamed(this.stringFrom(resultSet, 8));        // FKCOLUMN_NAME
        this.targetColumn = this.buildLocalColumn(this.stringFrom(resultSet, 4));        // PKCOLUMN_NAME
    }

    private String stringFrom(ResultSet resultSet, int colIndex) {
        try {
            return this.trim(resultSet.getString(colIndex));
        } catch (SQLException ex) {
            // defensive - return null if the requested column is not supported by the driver
            return null;
        }
    }

    /**
     * trim down the specified string, to null if necessary
     */
    private String trim(String s) {
        if (s == null) {
            return null;
        }
        s = s.trim();
        return (s.length() == 0) ? null : s;
    }


    // ********** ExternalForeignKeyColumnPair implementation **********

    /**
     * the source column can be null if we have problems reading the result set
     * @see org.eclipse.persistence.tools.workbench.mappingsmodel.spi.db.ExternalForeignKeyColumnPair#getSourceColumn()
     */
    public ExternalColumn getSourceColumn() {
        return this.sourceColumn;
    }

    /**
     * the target column can be null if we have problems reading the result set
     * @see org.eclipse.persistence.tools.workbench.mappingsmodel.spi.db.ExternalForeignKeyColumnPair#getTargetColumn()
     */
    public ExternalColumn getTargetColumn() {
        return this.targetColumn;
    }


    // ********** queries **********

    private JDBCExternalColumn columnNamed(String columnName) {
        return this.foreignKey.columnNamed(columnName);
    }

    private ExternalColumn buildLocalColumn(String columnName) {
        return (columnName == null) ? null : new TargetColumn(columnName);
    }

    private String sourceColumnName() {
        return (this.sourceColumn == null) ? null : this.sourceColumn.getName();
    }

    private String targetColumnName() {
        return (this.targetColumn == null) ? null : this.targetColumn.getName();
    }

    /**
     * @see Object#toString()
     */
    public String toString() {
        return StringTools.buildToStringFor(this, this.sourceColumnName() + "=>" + this.targetColumnName());
    }


    // ********** member class **********

    /**
     * this column can only return its name;
     * all other operations are unsupported
     */
    private static class TargetColumn implements ExternalColumn {
        private final String name;
        TargetColumn(String name) {
            super();
            if (name == null) {
                throw new NullPointerException();
            }
            this.name = name;
        }
        public String getName() {
            return this.name;
        }
        public int getJDBCTypeCode() {
            throw new UnsupportedOperationException();
        }
        public String getTypeName() {
            throw new UnsupportedOperationException();
        }
        public int getSize() {
            throw new UnsupportedOperationException();
        }
        public int getScale() {
            throw new UnsupportedOperationException();
        }
        public boolean isNullable() {
            throw new UnsupportedOperationException();
        }
        public boolean isPrimaryKey() {
            throw new UnsupportedOperationException();
        }
        public String toString() {
            return StringTools.buildToStringFor(this, this.name);
        }
    }

}