RdfSerializingWriter.java

/*
 * 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.stanbol.commons.web.rdfviewable.writer.impl;

import java.io.IOException;
import java.io.OutputStream;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import javax.ws.rs.Produces;
import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.core.UriInfo;
import javax.ws.rs.ext.MessageBodyWriter;
import javax.ws.rs.ext.Provider;
import org.apache.clerezza.commons.rdf.RDFTerm;
import org.apache.clerezza.commons.rdf.Triple;
import org.apache.clerezza.commons.rdf.Graph;
import org.apache.clerezza.commons.rdf.IRI;
import org.apache.clerezza.commons.rdf.impl.utils.PlainLiteralImpl;
import org.apache.clerezza.commons.rdf.impl.utils.simple.SimpleGraph;
import org.apache.clerezza.rdf.core.serializedform.Serializer;
import org.apache.clerezza.rdf.core.serializedform.SupportedFormat;
import org.apache.clerezza.rdf.utils.GraphNode;
import org.apache.felix.scr.annotations.Component;
import org.apache.felix.scr.annotations.Property;
import org.apache.felix.scr.annotations.Reference;
import org.apache.felix.scr.annotations.Service;
import org.apache.stanbol.commons.web.rdfviewable.writer.RECIPES;
import org.apache.stanbol.commons.web.rdfviewable.writer.RecipesGraphProvider;
import org.apache.stanbol.commons.web.viewable.RdfViewable;

/**
 * By default this returns a serialization of the context of the GraphNode. The
 * template path of the RdfViewable is used to look for a recipe to control the
 * expansion of the seriaization.
 *
 * Same as with
 * <code>org.apache.clerezza.jaxrs.rdf.providers</code> the expansion can be
 * widened by using the query parameters xPropObj and xProSubj. These parameters
 * specify property uris (both parameters might be repeated). For the specified
 * properties their objects respectively subjects are expanded as if they were
 * bnodes.
 *
 */
@Component
@Service(Object.class)
@Property(name = "javax.ws.rs", boolValue = true)
@Provider
@Produces({SupportedFormat.N3, SupportedFormat.N_TRIPLE,
    SupportedFormat.RDF_XML, SupportedFormat.TURTLE,
    SupportedFormat.X_TURTLE, SupportedFormat.RDF_JSON})
public class RdfSerializingWriter implements MessageBodyWriter<RdfViewable> {

    
    public static final String OBJ_EXP_PARAM = "xPropObj";
    public static final String SUBJ_EXP_PARAM = "xPropSubj";
    
    @Reference
    private Serializer serializer;
    
    @Reference
    private RecipesGraphProvider recipesGraphProvider;
    
    private UriInfo uriInfo;

    @Override
    public boolean isWriteable(Class<?> type, Type genericType,
            Annotation[] annotations, MediaType mediaType) {
        return RdfViewable.class.isAssignableFrom(type);
    }

    @Override
    public long getSize(RdfViewable n, Class<?> type, Type genericType,
            Annotation[] annotations, MediaType mediaType) {
        return -1;
    }

    @Override
    public void writeTo(RdfViewable v, Class<?> type, Type genericType,
            Annotation[] annotations, MediaType mediaType,
            MultivaluedMap<String, Object> httpHeaders,
            OutputStream entityStream) throws IOException, WebApplicationException {
        GraphNode node = v.getGraphNode();
        GraphNode recipe = getRecipe(v.getRenderingSpecification());
        serializer.serialize(entityStream, getExpandedContext(node, recipe), mediaType.toString());
    }

    @Context
    public void setUriInfo(UriInfo uriInfo) {
        this.uriInfo = uriInfo;
    }

    private Graph getExpandedContext(GraphNode node, GraphNode recipe) {
        final Graph result = new SimpleGraph(node.getNodeContext());
        final Set<RDFTerm> expandedResources = new HashSet<RDFTerm>();
        expandedResources.add(node.getNode());
        while (true) {
            Set<RDFTerm> additionalExpansionRes = getAdditionalExpansionResources(result, recipe);
            additionalExpansionRes.removeAll(expandedResources);
            if (additionalExpansionRes.size() == 0) {
                return result;
            }
            for (RDFTerm resource : additionalExpansionRes) {
                final GraphNode additionalNode = new GraphNode(resource, node.getGraph());
                result.addAll(additionalNode.getNodeContext());
                expandedResources.add(resource);
            }
        }
    }

    private Set<RDFTerm> getAdditionalExpansionResources(Graph tc, GraphNode recipe) {
        final Set<IRI> subjectExpansionProperties = getSubjectExpansionProperties(recipe);
        final Set<IRI> objectExpansionProperties = getObjectExpansionProperties(recipe);
        final Set<RDFTerm> result = new HashSet<RDFTerm>();
        if ((subjectExpansionProperties.size() > 0)
                || (objectExpansionProperties.size() > 0)) {
            for (Triple triple : tc) {
                final IRI predicate = triple.getPredicate();
                if (subjectExpansionProperties.contains(predicate)) {
                    result.add(triple.getSubject());
                }
                if (objectExpansionProperties.contains(predicate)) {
                    result.add(triple.getObject());
                }
            }
        }
        return result;
    }

    private Set<IRI> getSubjectExpansionProperties(GraphNode recipe) {
        final MultivaluedMap<String, String> queryParams = uriInfo.getQueryParameters(true);
        final List<String> paramValues = queryParams.get(SUBJ_EXP_PARAM);
        final Set<IRI> result = new HashSet<IRI>();
        if (paramValues != null) {
            for (String uriString : paramValues) {
                result.add(new IRI(uriString));
            }
        }
        if (recipe != null) {
            Iterator<GraphNode> ingredients = recipe.getObjectNodes(RECIPES.ingredient);
            while (ingredients.hasNext()) {
                Iterator<RDFTerm> properties = 
                        ingredients.next().getObjects(RECIPES.ingredientInverseProperty);
                while (properties.hasNext()) {
                    result.add((IRI)properties.next());
                }
            }
        }
        return result;
    }

    private Set<IRI> getObjectExpansionProperties(GraphNode recipe) {
        final MultivaluedMap<String, String> queryParams = uriInfo.getQueryParameters(true);
        final List<String> paramValues = queryParams.get(OBJ_EXP_PARAM);
        final Set<IRI> result = new HashSet<IRI>();
        if (paramValues != null) {
            for (String uriString : paramValues) {
                result.add(new IRI(uriString));
            }
        }
        if (recipe != null) {
            Iterator<GraphNode> ingredients = recipe.getObjectNodes(RECIPES.ingredient);
            while (ingredients.hasNext()) {
                Iterator<RDFTerm> properties = 
                        ingredients.next().getObjects(RECIPES.ingredientProperty);
                while (properties.hasNext()) {
                    result.add((IRI)properties.next());
                }
            }
        }
        
        return result;
    }

    private GraphNode getRecipe(String templatePath) {
        Graph rg = recipesGraphProvider.getRecipesGraph();
        GraphNode literalNode = new GraphNode(new PlainLiteralImpl(templatePath), rg);
        Iterator<GraphNode> recipes = literalNode.getSubjectNodes(RECIPES.recipeDomain);
        if (recipes.hasNext()) {
            return recipes.next();
        } else {
            return null;
        }
    }
}