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Kernel for Resin Java Application Server
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/*
* Copyright (c) 1998-2012 Caucho Technology -- all rights reserved
*
* This file is part of Resin(R) Open Source
*
* Each copy or derived work must preserve the copyright notice and this
* notice unmodified.
*
* Resin Open Source is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* Resin Open Source 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, or any warranty
* of NON-INFRINGEMENT. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License
* along with Resin Open Source; if not, write to the
*
* Free SoftwareFoundation, Inc.
* 59 Temple Place, Suite 330
* Boston, MA 02111-1307 USA
*
* @author Scott Ferguson
*/
package com.caucho.el;
import com.caucho.vfs.WriteStream;
import javax.el.ELContext;
import javax.el.ELException;
import java.io.IOException;
/**
* Represents a conditional expression
*/
public class ConditionalNullExpr extends Expr {
private Expr _value;
private Expr _defaultExpr;
/**
* Creates the conditional expression.
*
* @param test the conditional expressions test.
* @param trueExpr the true subexpression
* @param falseExpr the false subexpression
*/
public ConditionalNullExpr(Expr value, Expr defaultExpr)
{
_value = value;
_defaultExpr = defaultExpr;
}
/**
* Returns true if this is a constant expression.
*/
@Override
public boolean isConstant()
{
return (_value.isConstant() &&
_defaultExpr.isConstant());
}
/**
* Evaluate the expression as an object.
*
* @param env the variable environment
*
* @return the result as an object
*/
@Override
public Object getValue(ELContext env)
throws ELException
{
Object value = _value.getValue(env);
if (value != null && ! "".equals(value))
return value;
else
return _defaultExpr.getValue(env);
}
/**
* Prints the Java code to recreate the expr
*
* @param os the output stream to the *.java file
*/
@Override
public void printCreate(WriteStream os)
throws IOException
{
os.print("new com.caucho.el.ConditionalNullExpr(");
_value.printCreate(os);
os.print(", ");
_defaultExpr.printCreate(os);
os.print(")");
}
/**
* Returns true for equal strings.
*/
public boolean equals(Object o)
{
if (! (o instanceof ConditionalNullExpr))
return false;
ConditionalNullExpr expr = (ConditionalNullExpr) o;
return (_value.equals(expr._value) &&
_defaultExpr.equals(expr._defaultExpr));
}
/**
* Returns a readable representation of the expr.
*/
public String toString()
{
return "(" + _value + " ?: " + _defaultExpr + ")";
}
}