com.espertech.esper.client.soda.SelectClauseExpression Maven / Gradle / Ivy

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Complex event processing and event series analysis component
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/**************************************************************************************
 * Copyright (C) 2008 EsperTech, Inc. All rights reserved.                            *
 * http://esper.codehaus.org                                                          *
 * http://www.espertech.com                                                           *
 * ---------------------------------------------------------------------------------- *
 * The software in this package is published under the terms of the GPL license       *
 * a copy of which has been included with this distribution in the license.txt file.  *
 **************************************************************************************/
package com.espertech.esper.client.soda;

import java.io.StringWriter;

/**
 * Part of a select-clause to describe individual select-clause expressions.
 */
public class SelectClauseExpression implements SelectClauseElement
{
    private static final long serialVersionUID = 0L;

    private Expression expression;
    private String asName;

    /**
     * Ctor.
     */
    public SelectClauseExpression() {
    }

    /**
     * Ctor.
     * @param expression is the selection expression
     */
    public SelectClauseExpression(Expression expression)
    {
        this.expression = expression;
    }

    /**
     * Ctor.
     * @param expression is the selection expression
     * @param optionalAsName is the "as"-tag for the expression
     */
    public SelectClauseExpression(Expression expression, String optionalAsName)
    {
        this.expression = expression;
        this.asName = optionalAsName;
    }

    /**
     * Returns the selection expression.
     * @return expression
     */
    public Expression getExpression()
    {
        return expression;
    }

    /**
     * Sets the selection expression.
     * @param expression is the selection expression
     */
    public void setExpression(Expression expression)
    {
        this.expression = expression;
    }

    /**
     * Returns the optional "as"-name of the expression, or null if not defined
     * @return tag or null for selection expression
     */
    public String getAsName()
    {
        return asName;
    }

    /**
     * Sets the optional "as"-name of the expression, or null if not defined
     * @param asName column name or null for selection expression
     */
    public void setAsName(String asName)
    {
        this.asName = asName;
    }

    /**
     * Renders the element in textual representation.
     * @param writer to output to
     */
    public void toEPLElement(StringWriter writer)
    {
        expression.toEPL(writer, ExpressionPrecedenceEnum.MINIMUM);
        if (asName != null)
        {
            writer.write(" as ");
            writer.write(asName);
        }
    }
}