/*
* 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.clerezza.rdf.web.core;
import java.io.OutputStream;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.ext.MessageBodyWriter;
import javax.ws.rs.ext.Provider;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.IOException;
import java.util.HashSet;
import java.util.Set;
import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.Response;
import javax.ws.rs.core.Response.Status;
import javax.ws.rs.ext.Providers;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Source;
import javax.xml.transform.dom.DOMSource;
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.clerezza.rdf.core.BNode;
import org.apache.clerezza.rdf.core.Language;
import org.apache.clerezza.rdf.core.PlainLiteral;
import org.apache.clerezza.rdf.core.Resource;
import org.apache.clerezza.rdf.core.TypedLiteral;
import org.apache.clerezza.rdf.core.UriRef;
import org.apache.clerezza.rdf.core.access.TcManager;
import org.apache.clerezza.rdf.core.sparql.ResultSet;
import org.apache.clerezza.rdf.core.sparql.SolutionMapping;
import org.apache.clerezza.rdf.core.sparql.query.Variable;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
/**
* MessageBodyWirter for <code>ResultSet</code>.
*
* @author mir, reto
*/
@Component
@Service(Object.class)
@Property(name="javax.ws.rs", boolValue=true)
@Produces({"application/xml", "text/xml", "application/sparql-results+xml"})
@Provider
public class ResultSetMessageBodyWriter implements MessageBodyWriter<ResultSet> {
@Reference
TcManager tcManager;
private Providers providers;
final Logger logger = LoggerFactory.getLogger(ResultSetMessageBodyWriter.class);
@Override
public boolean isWriteable(Class<?> type, Type genericType, Annotation[] annotations,
MediaType mediaType) {
return ResultSet.class.isAssignableFrom(type);
}
@Override
public long getSize(ResultSet t, Class<?> type, Type genericType,
Annotation[] annotations, MediaType mediaType) {
return -1;
}
@Override
public void writeTo(ResultSet resultSet, Class<?> type, Type genericType,
Annotation[] annotations, MediaType mediaType, MultivaluedMap<String,
Object> httpHeaders, OutputStream entityStream) throws IOException, WebApplicationException {
Source source = toXmlSource(resultSet);
MessageBodyWriter<Source> sourceMessageBodyWriter =
providers.getMessageBodyWriter(Source.class, null, null, mediaType);
sourceMessageBodyWriter.writeTo(source, Source.class, null, null, mediaType,
httpHeaders, entityStream);
}
@Context
public void setProviders(Providers providers) {
this.providers = providers;
}
/**
* Helper: transforms a {@link ResultSet} or a {@link Boolean} to a
* {@link DOMSource}
*
* @param queryResult
* @param query
* @param applyStyle
*/
private Source toXmlSource(ResultSet queryResult) {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
try {
Document doc = dbf.newDocumentBuilder().newDocument();
// adding root element
Element root = doc.createElement("sparql");
root.setAttribute("xmlns", "http://www.w3.org/2005/sparql-results#");
doc.appendChild(root);
Element head = doc.createElement("head");
root.appendChild(head);
Set<Object> variables = new HashSet<Object>();
Element results = doc.createElement("results");
SolutionMapping solutionMapping = null;
while (queryResult.hasNext()) {
solutionMapping = queryResult.next();
createResultElement(solutionMapping, results, doc);
}
createVariable(solutionMapping, head, doc);
root.appendChild(results);
DOMSource source = new DOMSource(doc);
return source;
} catch (ParserConfigurationException e) {
throw createWebApplicationException(e);
}
}
/**
* Creates a WebApplicationexception and prints a logger entry
*/
private WebApplicationException createWebApplicationException(Exception e) {
return new WebApplicationException(Response.status(Status.BAD_REQUEST)
.entity(e.getMessage().replace("<", "<").replace("\n",
"<br/>")).build());
}
/**
* Helper: creates value element from {@link Resource} depending on its
* class
*
*/
private Element createValueElement(Resource resource, Document doc) {
Element value = null;
if (resource instanceof UriRef) {
value = doc.createElement("uri");
value.appendChild(doc.createTextNode(((UriRef) resource)
.getUnicodeString()));
} else if (resource instanceof TypedLiteral) {
value = doc.createElement("literal");
value.appendChild(doc.createTextNode(((TypedLiteral) resource)
.getLexicalForm()));
value.setAttribute("datatype", (((TypedLiteral) resource)
.getDataType().getUnicodeString()));
} else if (resource instanceof PlainLiteral) {
value = doc.createElement("literal");
value.appendChild(doc.createTextNode(((PlainLiteral) resource)
.getLexicalForm()));
Language lang = ((PlainLiteral) resource).getLanguage();
if (lang != null) {
value.setAttribute("xml:lang", (lang.toString()));
}
} else {
value = doc.createElement("bnode");
value.appendChild(doc.createTextNode(((BNode) resource).toString()));
}
return value;
}
/**
* Helper: creates results element from ResultSet
*
*/
private void createResultElement(SolutionMapping solutionMap, Element results, Document doc) {
Set<Variable> keys = solutionMap.keySet();
Element result = doc.createElement("result");
results.appendChild(result);
for (Variable key : keys) {
Element bindingElement = doc.createElement("binding");
bindingElement.setAttribute("name", key.getName());
bindingElement.appendChild(createValueElement(
(Resource) solutionMap.get(key), doc));
result.appendChild(bindingElement);
}
}
private void createVariable(SolutionMapping solutionMap, Element head, Document doc) {
Set<Variable> keys = solutionMap.keySet();
for (Variable key : keys) {
Element varElement = doc.createElement("variable");
varElement.setAttribute("name", key.getName());
head.appendChild(varElement);
}
}
}