/*
* Copyright 2008 Fedora Commons, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.mulgara.query.filter;
import java.util.Collections;
import java.util.Set;
import org.jrdf.graph.Node;
import org.mulgara.query.rdf.LiteralImpl;
import org.mulgara.query.rdf.XSD;
import org.mulgara.query.QueryException;
import org.mulgara.query.Variable;
/**
* Filters the iteration of a Constraint.
* TODO: This is more properly called an Expression, since they can be used in non-filter roles.
*
* @created Mar 7, 2008
* @author Paula Gearon
* @copyright © 2008 <a href="http://www.fedora-commons.org/">Fedora Commons</a>
*/
public interface Filter extends ContextOwner, RDFTerm {
/**
* Tests a binding according to the filter.
* @param context The context to resolve the filter in.
* @return <code>true</code> when the filter is matched.
* @throws QueryException The filter found an error during testing.
*/
public boolean test(Context context) throws QueryException;
/** A filter that does no filtering. */
public static final Filter NULL = new Filter() {
private static final long serialVersionUID = -1561779107566375359L;
public boolean test(Context context) { return true; }
public void setCurrentContext(Context context) { }
public Context getCurrentContext() { return null; }
// RDFTerm methods
public boolean equals(RDFTerm v) throws QueryException { return v == this; }
public ContextOwner getContextOwner() { return null; }
public Object getValue() throws QueryException { return true; }
public Node getJRDFValue() throws QueryException { return new LiteralImpl("true", XSD.BOOLEAN_URI); }
public boolean isBlank() throws QueryException { return false; }
public boolean isIRI() throws QueryException { return false; }
public boolean isLiteral() throws QueryException { return true; }
public boolean isURI() throws QueryException { return false; }
public boolean isGrounded() throws QueryException { return true; }
public boolean sameTerm(RDFTerm v) throws QueryException { return equals(v); }
public void setContextOwner(ContextOwner owner) { }
public void addContextListener(ContextOwner l) { }
public Set<Variable> getVariables() { return Collections.emptySet(); }
};
}