/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 2014, 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.jdbc;
import java.util.ArrayList;
import java.util.List;
import org.geotools.filter.visitor.DuplicatingFilterVisitor;
import org.opengis.feature.type.FeatureType;
import org.opengis.feature.type.PropertyDescriptor;
import org.opengis.filter.And;
import org.opengis.filter.BinaryComparisonOperator;
import org.opengis.filter.Filter;
import org.opengis.filter.Not;
import org.opengis.filter.PropertyIsBetween;
import org.opengis.filter.PropertyIsEqualTo;
import org.opengis.filter.PropertyIsGreaterThan;
import org.opengis.filter.PropertyIsGreaterThanOrEqualTo;
import org.opengis.filter.PropertyIsLessThan;
import org.opengis.filter.PropertyIsLessThanOrEqualTo;
import org.opengis.filter.PropertyIsLike;
import org.opengis.filter.PropertyIsNotEqualTo;
import org.opengis.filter.expression.Expression;
import org.opengis.filter.expression.PropertyName;
/**
* Amends the differences between our in-memory two-valued logic and the database own three-valued
* logic making sure we treat null values just like in memory (avoiding the third "unkonwn" status)
*
* @author Andrea Aime - GeoSolutions
*/
class NullHandlingVisitor extends DuplicatingFilterVisitor {
private FeatureType schema;
/**
* When providing the schema, the attributes will have null checks added only if they are marked
* as nillable
*/
public NullHandlingVisitor(FeatureType schema) {
this.schema = schema;
}
public NullHandlingVisitor() {
}
public Object visit(PropertyIsEqualTo filter, Object extraData) {
return guardAgainstNulls((BinaryComparisonOperator) super.visit(filter, extraData));
}
public Object visit(PropertyIsNotEqualTo filter, Object extraData) {
return guardAgainstNulls((BinaryComparisonOperator) super.visit(filter, extraData));
}
public Object visit(PropertyIsGreaterThan filter, Object extraData) {
return guardAgainstNulls((BinaryComparisonOperator) super.visit(filter, extraData));
}
public Object visit(PropertyIsGreaterThanOrEqualTo filter, Object extraData) {
return guardAgainstNulls((BinaryComparisonOperator) super.visit(filter, extraData));
}
public Object visit(PropertyIsLessThan filter, Object extraData) {
return guardAgainstNulls((BinaryComparisonOperator) super.visit(filter, extraData));
}
public Object visit(PropertyIsLessThanOrEqualTo filter, Object extraData) {
return guardAgainstNulls((BinaryComparisonOperator) super.visit(filter, extraData));
}
private Object guardAgainstNulls(BinaryComparisonOperator clone) {
Filter result = guardAgainstNulls(clone, clone.getExpression1());
result = guardAgainstNulls(result, clone.getExpression2());
return result;
}
@Override
public Object visit(PropertyIsLike filter, Object extraData) {
PropertyIsLike clone = (PropertyIsLike) super.visit(filter, extraData);
return guardAgainstNulls(filter, clone.getExpression());
}
public Object visit(PropertyIsBetween filter, Object extraData) {
PropertyIsBetween clone = (PropertyIsBetween) super.visit(filter, extraData);
Filter f = guardAgainstNulls(clone, clone.getExpression());
f = guardAgainstNulls(f, clone.getLowerBoundary());
f = guardAgainstNulls(f, clone.getUpperBoundary());
return f;
}
/**
* Guards the filter against potential null values in the target property name (if it is a
* property name, to start with)
*/
private Filter guardAgainstNulls(Filter filter, Expression potentialPropertyName) {
if (potentialPropertyName instanceof PropertyName) {
PropertyName pn = (PropertyName) potentialPropertyName;
String name = pn.getPropertyName();
if (isNillable(name)) {
Not notNull = ff.not(ff.isNull(ff.property(name)));
if (filter instanceof And) {
And and = (And) filter;
List<Filter> children = new ArrayList<Filter>(and.getChildren());
children.add(notNull);
return ff.and(children);
} else {
return ff.and(filter, notNull);
}
}
}
return filter;
}
/**
* Returns if a property can contain null values, or not. If we don't have the schema
* information, or we don't know the property, we are going to assume the property is nillable
* to stay on the safe side
*/
private boolean isNillable(String name) {
if (schema == null) {
return true;
}
PropertyDescriptor descriptor = schema.getDescriptor(name);
return descriptor == null || descriptor.isNillable();
}
}