AliasSymbol.java

/*
 * JBoss, Home of Professional Open Source.
 * See the COPYRIGHT.txt file distributed with this work for information
 * regarding copyright ownership.  Some portions may be licensed
 * to Red Hat, Inc. under one or more contributor license agreements.
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301 USA.
 */

package org.teiid.query.sql.symbol;

import org.teiid.core.util.Assertion;
import org.teiid.query.QueryPlugin;
import org.teiid.query.sql.LanguageVisitor;


/**
 * An AliasSymbol wraps a SingleElementSymbol and changes it's name.  AliasSymbols
 * should be used to perform the aliasing of elements in a SELECT clause.  They
 * should typically NOT be used elsewhere in a query.  The alias symbol takes on
 * the type of it's underlying SingleElementSymbol.  AliasSymbols are typically
 * applied to ElementSymbol, ExpressionSymbol, and AggregateSymbol.
 */
public class AliasSymbol extends Symbol implements DerivedExpression {

	private Expression symbol;

    /**
     * Constructor used for cloning 
     * @param name
     * @param canonicalName
     * @since 4.3
     */
    private AliasSymbol(String name, String canonicalName, Expression symbol) {
        super(name);
        setSymbol(symbol);
    }
    
	/**
	 * Construct an AliasSymbol given the alias name and the underlying symbol.
	 * @param name Name of the alias
	 * @param symbol Underlying symbol
	 */
	public AliasSymbol(String name, Expression symbol) {
		super(name);
        setSymbol(symbol);
	}

	/**
	 * Get the underlying symbol
	 * @return Underlying symbol
	 */
	public Expression getSymbol() {
		return this.symbol;
	}

	/**
	 * Set the underlying symbol
	 * @param symbol New symbol
	 */
	public void setSymbol(Expression symbol) {
        if(symbol instanceof AliasSymbol || symbol == null){
            Assertion.failed(QueryPlugin.Util.getString("ERR.015.010.0029")); //$NON-NLS-1$
        }
		this.symbol = symbol;
	}

	/**
	 * Get the type of the symbol
	 * @return Type of the symbol
	 */
	public Class<?> getType() {
		return this.symbol.getType();
	}

    public void acceptVisitor(LanguageVisitor visitor) {
        visitor.visit(this);
    }

	/**
	 * Return a copy of this object.
	 */
	public Object clone() {
		Expression symbolCopy = (Expression) this.symbol.clone();
		AliasSymbol result = new AliasSymbol(getName(), getShortName(), symbolCopy);
		result.outputName = this.outputName;
		return result;
	}
	
   /** 
     * @see org.teiid.query.sql.symbol.Symbol#equals(java.lang.Object)
     */
    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (!(obj instanceof AliasSymbol)) {
            return false;
        }
        AliasSymbol other = (AliasSymbol)obj;
        return this.getName().equals(other.getName()) && this.symbol.equals(other.symbol);
    }

}