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Core Implementation of LD Path a simple path-based query language similar to XPath or SPARQL Property Paths that is particularly well-suited for querying and retrieving resources from the Linked Data Cloud by following RDF links between resources and servers.

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/*
 * Copyright (c) 2011 Salzburg Research.
 *
 * 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 at.newmedialab.ldpath.model.selectors;

import at.newmedialab.ldpath.api.backend.RDFBackend;
import at.newmedialab.ldpath.api.selectors.NodeSelector;

import java.util.Collection;
import java.util.Collections;

/**
 * Add file description here!
 * 
 * Author: Sebastian Schaffert 
 */
public class StringConstantSelector implements NodeSelector {

	private String constant;

	public StringConstantSelector(String constant) {
		this.constant = constant;
	}

    /**
     * Apply the selector to the context node passed as argument and return the collection
     * of selected nodes in appropriate order.
     *
     * @param context the node where to start the selection
     * @return the collection of selected nodes
     */
    @Override
    public Collection select(RDFBackend rdfBackend, Node context) {
		return Collections.singleton(rdfBackend.createLiteral(constant));
	}

    /**
     * Return the name of the NodeSelector for registration in the selector registry
     *
     * @param rdfBackend
     * @return
     */
    @Override
    public String getPathExpression(RDFBackend rdfBackend) {
		return String.format("\"%s\"", constant);
	}


    /**
     * Return a name for this selector to be used as the name for the whole path if not explicitly
     * specified. In complex selector expressions, this is typically delegated to the first
     * occurrence of an atomic selector.
     */
    @Override
    public String getName(RDFBackend nodeRDFBackend) {
        return constant;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        StringConstantSelector that = (StringConstantSelector) o;

        if (constant != null ? !constant.equals(that.constant) : that.constant != null) return false;

        return true;
    }

    @Override
    public int hashCode() {
        return constant != null ? constant.hashCode() : 0;
    }
}