SubstitutionParameterExpression.java

/**************************************************************************************
 * 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.epl.spec;

import com.espertech.esper.client.soda.ExpressionBase;
import com.espertech.esper.client.soda.ExpressionPrecedenceEnum;
import com.espertech.esper.core.service.EPStatementObjectModelHelper;

import java.io.StringWriter;

/**
 * Substitution parameter that represents a node in an expression tree for which to supply a parameter value
 * before statement creation time.
 */
public class SubstitutionParameterExpression extends ExpressionBase
{
    private final int index;
    private Object constant;
    private boolean isSatisfied;
    private static final long serialVersionUID = -2310287186517093069L;

    /**
     * Ctor.
     * @param index is the index of the substitution parameter
     */
    public SubstitutionParameterExpression(int index)
    {
        this.index = index;
    }

    public ExpressionPrecedenceEnum getPrecedence()
    {
        return ExpressionPrecedenceEnum.UNARY;
    }

    public void toPrecedenceFreeEPL(StringWriter writer)
    {
        if (!isSatisfied)
        {
            writer.write("?");
        }
        else
        {
            EPStatementObjectModelHelper.renderEPL(writer, constant);
        }
    }

    /**
     * Returns the constant value that the expression represents.
     * @return value of constant
     */
    public Object getConstant()
    {
        return constant;
    }

    /**
     * Returns true if the parameter is satisfied, or false if not.
     * @return true if the actual value is supplied, false if not
     */
    public boolean isSatisfied()
    {
        return isSatisfied;
    }

    /**
     * Returns the index of the parameter.
     * @return parameter index.
     */
    public int getIndex()
    {
        return index;
    }

    /**
     * Sets the constant value that the expression represents.
     * @param constant is the value, or null to indicate the null value
     */
    public void setConstant(Object constant)
    {
        this.constant = constant;
        isSatisfied = true;
    }
}