/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 2006-2008, 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.spatial;
import org.geotools.filter.GeometryFilterImpl;
import org.opengis.filter.FilterFactory;
import org.opengis.filter.expression.Expression;
import org.opengis.filter.expression.Literal;
import com.vividsolutions.jts.geom.Geometry;
import com.vividsolutions.jts.geom.prep.PreparedGeometry;
import com.vividsolutions.jts.geom.prep.PreparedGeometryFactory;
/**
* A base class for GeometryFilters that will use PreparedGeometries when the Expression
* is a Literal Expression.
*
* <p>
* This class determines when the expressions are set which expressions are literals. The protected
* field {@link #literals} contains the {@link Literals} enumerated value that indicates if:
* </p>
* <ul>
* <li><strong>NEITHER</strong> ({@link Literals#NEITHER) of the expressions are literal and is a JTS Geometry (also non-null)</li>
* <li><strong>BOTH</strong> ({@link Literals#BOTH}) expressions are literals and is a JTS Geometry (also non-null)</li>
* <li>the <strong>LEFT</strong> ({@link Literals#LEFT}) expression (Expression1) is a literal and is a JTS Geometry (also non-null)</li>
* <li>or the <strong>RIGHT</strong> ({@link Literals#RIGHT}) expression (Expression2) is a literal and is a JTS Geometry (also non-null)</li>
* </ul>
* <p>
* If <strong>BOTH</strong> of the expressions are literals then a cached value is generated by calling {@link #basicEvaluate(Geometry, Geometry)}.
* </p>
* <p>
* The method {@link #basicEvaluate(Geometry, Geometry)} is required to be implemented so that a cached value can be generated in the case
* that both expressions are literals
* </p>
* <hr/><br>
* Example usage for intersects filter:
* <pre><code>
public boolean evaluate(Object feature) {
if (feature instanceof SimpleFeature
&& !validate((SimpleFeature) feature)) {
// we could not obtain a geometry for both left and right hand sides
// so default to false
return false;
}
Geometry left;
Geometry right;
switch (literals) {
case BOTH:
return cacheValue;
case RIGHT: {
return rightPreppedGeom.intersects(getLeftGeometry(feature));
}
case LEFT: {
return leftPreppedGeom.intersects(getRightGeometry(feature));
}
default: {
left = getLeftGeometry(feature);
right = getRightGeometry(feature);
return basicEvaluate(left, right);
}
}
}
protected final boolean basicEvaluate(Geometry left, Geometry right) {
Envelope envLeft = left.getEnvelopeInternal();
Envelope envRight = right.getEnvelopeInternal();
return envRight.intersects(envLeft) && left.intersects(right);
}
</code></pre>
* </p>
*
* @author jesse
*
*
* @source $URL$
*/
public abstract class AbstractPreparedGeometryFilter extends GeometryFilterImpl {
/**
* Constant that identifies which expressions are Literal and JTS Geometries
*
* @author jesse
*/
protected enum Literals {
/**
* Neither Expression are {@link Literal}s
*/
NEITHER,
/**
* Expression2 the "right" geometry is a {@link Literal}
*/
RIGHT,
/**
* Expression1 the "left" geometry is a {@link Literal}
*/
LEFT,
/**
* Both expressions are {@link Literal} expressions
*/
BOTH;
private static Literals calculate(Expression expression1,
Expression expression2) {
boolean left = expression1 instanceof Literal && ((Literal)expression1).getValue() instanceof Geometry;
boolean right = expression2 instanceof Literal && ((Literal)expression2).getValue() instanceof Geometry;
if (left && right) {
return BOTH;
}
if (left) {
return LEFT;
}
if (right) {
return RIGHT;
}
return NEITHER;
}
}
private final PreparedGeometryFactory pGeomFac;
/**
* Indicates which expressions are {@link Literal}s
*/
protected Literals literals;
/**
* The PreparedGeometry for the left Geometry. Null if the left geometry is not a
* {@link Literal}
*/
protected PreparedGeometry leftPreppedGeom;
/**
* The PreparedGeometry for the right Geometry. Null if the right geometry is not a
* {@link Literal}
*/
protected PreparedGeometry rightPreppedGeom;
/**
* If both expressions are literals the value will never change. In that
* case this field is that calculated value. It is false otherwise.
*/
protected boolean cacheValue;
protected AbstractPreparedGeometryFilter(FilterFactory factory,
Expression e1, Expression e2) {
super(factory, e1, e2);
pGeomFac = new PreparedGeometryFactory();
if( e1!=null ) setExpression1(e1);
if( e2!=null ) setExpression2(e2);
}
private void prepare() {
if( expression1==null || expression2==null ){
// filter not yet fully configured so wait
return;
}
literals = Literals.calculate(expression1, expression2);
switch (literals) {
case BOTH: {
Geometry left = (Geometry) ((Literal) expression1).getValue();
Geometry right = (Geometry) ((Literal) expression2).getValue();
cacheValue = basicEvaluate(left, right);
leftPreppedGeom = rightPreppedGeom = null;
break;
}
case LEFT: {
Geometry left = (Geometry) ((Literal) expression1).getValue();
leftPreppedGeom = pGeomFac.create(left);
rightPreppedGeom = null;
cacheValue = false;
break;
}
case RIGHT: {
Geometry right = (Geometry) ((Literal) expression2).getValue();
rightPreppedGeom = pGeomFac.create(right);
leftPreppedGeom = null;
cacheValue = false;
break;
}
default: {
leftPreppedGeom = rightPreppedGeom = null;
cacheValue = false;
}
}
}
@Override
public void setExpression1(Expression expression) {
super.setExpression1(expression);
prepare();
}
@Override
public void setExpression2(Expression expression) {
super.setExpression2(expression);
prepare();
}
/**
* Performs the calculation on the two geometries. This is used to calculate the cached value
* in the case that both geometries are Literals. But in practice it is useful to extract this functionality
* into its own method.
*
* @param left the geometry on the left of the equations (the geometry obtained from evaluating Expression1)
* @param right the geometry on the right of the equations (the geometry obtained from evaluating Expression2)
* @return true if the filter evaluates to true for the two geometries
*/
protected abstract boolean basicEvaluate(Geometry left, Geometry right);
}