/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 2002-2008, Open Source Geospatial Foundation (OSGeo)
*
* 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;
* version 2.1 of the License.
*
* 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.
*/
package org.geotools.filter.visitor;
import org.opengis.filter.expression.Add;
import org.opengis.filter.expression.Divide;
import org.opengis.filter.expression.Expression;
import org.opengis.filter.expression.ExpressionVisitor;
import org.opengis.filter.expression.Function;
import org.opengis.filter.expression.Literal;
import org.opengis.filter.expression.Multiply;
import org.opengis.filter.expression.NilExpression;
import org.opengis.filter.expression.PropertyName;
import org.opengis.filter.expression.Subtract;
/**
* Check if an expression is static (ie does not contain a PropertyName expression).
* <p>
* This visitor will "short-circuit" the moment it finds a PropertyName expression
* and will not need to visit the entire data structure.
* <p>
* Example:<pre><code>
* if( filter.accepts( IsStaticExpressionVisitor.VISITOR, null ) ){
* Color color = expression.evaulate( null, Color.class );
* ...
* }
* </code></pre>
*
* @author Jody
*
*
* @source $URL$
*/
public class IsStaticExpressionVisitor implements ExpressionVisitor {
public static final IsStaticExpressionVisitor VISITOR = new IsStaticExpressionVisitor();
/** visit each expression and check that they are static */
protected IsStaticExpressionVisitor() {
}
/** visit each expression and check that they are static */
public Boolean visit( NilExpression expression, Object data ) {
return true;
}
/** visit each expression and check that they are static */
public Boolean visit( Add expression, Object data ) {
boolean isStatic;
isStatic = (Boolean) expression.getExpression1().accept( this, data);
if( isStatic == false ) return false;
isStatic = (Boolean) expression.getExpression2().accept( this, data);
return isStatic;
}
/** visit each expression and check that they are static */
public Boolean visit( Divide expression, Object data ) {
boolean isStatic;
isStatic = (Boolean) expression.getExpression1().accept( this, data);
if( isStatic == false ) return false;
isStatic = (Boolean) expression.getExpression2().accept( this, data);
return isStatic;
}
/**
* Visit each parameter and check if they are static
*/
public Boolean visit( Function expression, Object data ) {
boolean isStatic = true;
if( expression.getParameters() != null ){
for( Expression parameter : expression.getParameters() ){
isStatic = (Boolean) parameter.accept( this, data);
if( isStatic == false ) break;
}
}
return isStatic;
}
/**
* Literal expressions are always static.
* @return true
*/
public Boolean visit( Literal expression, Object data ) {
return true;
}
/** visit each expression and check that they are static.
* @return true if getExpression1 and getExpression2 are static
*/
public Boolean visit( Multiply expression, Object data ) {
boolean isStatic;
isStatic = (Boolean) expression.getExpression1().accept( this, data);
if( isStatic == false ) return false;
isStatic = (Boolean) expression.getExpression2().accept( this, data);
return isStatic;
}
/**
* If even a single PropertyName is found in the expression
* the expression is not static.
* @return false
*/
public Boolean visit( PropertyName expression, Object data ) {
return false;
}
/** visit each expression and check that they are static.
* @return true if getExpression1 and getExpression2 are static
*/
public Boolean visit( Subtract expression, Object data ) {
boolean isStatic;
isStatic = (Boolean) expression.getExpression1().accept( this, data);
if( isStatic == false ) return false;
isStatic = (Boolean) expression.getExpression2().accept( this, data);
return isStatic;
}
}