MWColumnHandle.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.handles;

import org.eclipse.persistence.tools.workbench.mappingsmodel.MWModel;
import org.eclipse.persistence.tools.workbench.mappingsmodel.db.MWColumn;
import org.eclipse.persistence.tools.workbench.mappingsmodel.db.MWTable;
import org.eclipse.persistence.tools.workbench.utility.node.Node;

import org.eclipse.persistence.descriptors.ClassDescriptor;
import org.eclipse.persistence.mappings.OneToOneMapping;
import org.eclipse.persistence.oxm.XMLDescriptor;

/**
 * MWColumnHandle is used to isolate the painful bits of code
 * necessary to correctly handle references to MWColumns.
 * Since a MWColumn is nested within the XML file
 * for a MWTable, we need to store a reference to a particular
 * column as a pair of instance variables:
 *   - the name of the containing table
 *   - the name of the column
 *
 * This causes no end of pain when dealing with TopLink, property
 * change listeners, backward-compatibility, etc.
 */
public final class MWColumnHandle extends MWHandle {

    /**
     * This is the actual column.
     * It is built from the table and column names, below.
     */
    private volatile MWColumn column;

    /**
     * The table and column names are transient. They
     * are used only to hold their values until postProjectBuild()
     * is called and we can resolve the actual column.
     * We do not keep these in synch with the column itself because
     * we cannot know when the column has been renamed etc.
     */
    private volatile String columnTableName;
    private volatile String columnName;


    // ********** constructors **********

    /**
     * default constructor - for TopLink use only
     */
    private MWColumnHandle() {
        super();
    }

    public MWColumnHandle(MWModel parent, NodeReferenceScrubber scrubber) {
        super(parent, scrubber);
    }

    public MWColumnHandle(MWModel parent, MWColumn column, NodeReferenceScrubber scrubber) {
        super(parent, scrubber);
        this.column = column;
    }


    // ********** instance methods **********

    public MWColumn getColumn() {
        return this.column;
    }

    public void setColumn(MWColumn column) {
        this.column = column;
    }

    protected Node node() {
        return this.getColumn();
    }

    /**
     * Override to delegate comparison to the column itself.
     * If the handles being compared are in a collection that is being sorted,
     * NEITHER column should be null.
     */
    public int compareTo(Object o) {
        return this.column.compareTo(((MWColumnHandle) o).column);
    }

    public void toString(StringBuffer sb) {
        if (this.column == null) {
            sb.append("null");
        } else {
            this.column.toString(sb);
        }
    }

    public MWColumnHandle setScrubber(NodeReferenceScrubber scrubber) {
        this.setScrubberInternal(scrubber);
        return this;
    }

    public void resolveColumnHandles() {
        super.resolveColumnHandles();

        if (this.columnTableName != null && this.columnName != null) {
            MWTable table = this.getDatabase().tableNamed(this.columnTableName);
            if (table != null) {
                this.column = table.columnNamed(this.columnName);
            }
        }

        // Ensure columnTableName and columnName are not used by setting them to null....
        // If the XML is corrupt and only one of these attributes is populated,
        // this will cause the populated attribute to be cleared out if the
        // objects are rewritten.
        this.columnTableName = null;
        this.columnName = null;
    }


    // ********** TopLink methods **********

    public static XMLDescriptor buildDescriptor() {
        XMLDescriptor descriptor = new XMLDescriptor();

        descriptor.setJavaClass(MWColumnHandle.class);

        descriptor.addDirectMapping("columnTableName", "getColumnTableNameForTopLink", "setColumnTableNameForTopLink", "column-table-name/text()");
        descriptor.addDirectMapping("columnName", "getColumnNameForTopLink", "setColumnNameForTopLink", "column-name/text()");

        return descriptor;
    }

    private String getColumnTableNameForTopLink(){
        return (this.column == null) ? null : this.column.getTable().getName();
    }
    private void setColumnTableNameForTopLink(String columnTableName){
        this.columnTableName = columnTableName;
    }

    private String getColumnNameForTopLink() {
        return (this.column == null) ? null : this.column.getName();
    }
    private void setColumnNameForTopLink(String columnName) {
        this.columnName = columnName;
    }

}