/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.apache.jena.sparql.function.library;
import org.apache.jena.atlas.lib.Lib ;
import org.apache.jena.graph.Node ;
import org.apache.jena.sparql.engine.binding.Binding ;
import org.apache.jena.sparql.expr.ExprEvalException ;
import org.apache.jena.sparql.expr.ExprException ;
import org.apache.jena.sparql.expr.ExprList ;
import org.apache.jena.sparql.expr.NodeValue ;
import org.apache.jena.sparql.function.Function ;
import org.apache.jena.sparql.function.FunctionEnv ;
import org.apache.jena.sparql.util.Symbol ;
/**
* Function that returns the value of a system variable.
*/
public class SystemVar implements Function
{
private Symbol systemSymbol ;
protected SystemVar(Symbol systemSymbol)
{
if ( systemSymbol == null )
throw new ExprException("System symbol is null ptr") ;
this.systemSymbol = systemSymbol ;
}
// Need to intercept exec so we can get to the FunctionEnv
@Override
public NodeValue exec(Binding binding, ExprList args, String uri, FunctionEnv env) {
// Ignore arguments.
Object obj = env.getContext().get(systemSymbol) ;
if ( obj == null )
throw new ExprEvalException("null for system symbol: "+systemSymbol) ;
if ( ! ( obj instanceof Node ) )
throw new ExprEvalException("Not a Node: "+Lib.className(obj)) ;
Node n = (Node)obj ;
// if ( n == null )
// throw new ExprEvalException("No value for system variable: "+systemSymbol) ;
// NodeValue.makeNode could have a cache.
NodeValue nv = NodeValue.makeNode(n) ;
return nv ;
}
@Override
public void build(String uri, ExprList args) {}
}