/*
* 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.jaxrs.sparql.providers;
import java.io.IOException;
import java.io.OutputStream;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;
import java.util.List;
import java.util.Set;
import javax.ws.rs.Produces;
import javax.ws.rs.WebApplicationException;
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.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.sparql.ResultSet;
import org.apache.clerezza.rdf.core.sparql.SolutionMapping;
import org.apache.clerezza.rdf.core.sparql.query.Variable;
import org.apache.felix.scr.annotations.Component;
import org.apache.felix.scr.annotations.Property;
import org.apache.felix.scr.annotations.Service;
import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* MessageBodyWirter for <code>ResultSet</code>.
* Resulting output conforms to:
* http://www.w3.org/TR/2007/NOTE-rdf-sparql-json-res-20070618/
*
* @author misl
*/
@Component
@Service(Object.class)
@Property(name="javax.ws.rs", boolValue=true)
@Produces({"application/json", "application/sparql-results+json"})
@Provider
@SuppressWarnings("unchecked")
public class ResultSetJsonMessageBodyWriter implements MessageBodyWriter<ResultSet> {
final Logger logger = LoggerFactory.getLogger(ResultSetJsonMessageBodyWriter.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 {
JSONObject json = toJsonSource(resultSet);
entityStream.write(json.toJSONString().getBytes("UTF-8"));
}
/**
* Helper: transforms a {@link ResultSet} or a {@link Boolean} to a
* json object.
*
* @param queryResult
*/
private JSONObject toJsonSource(ResultSet queryResult) {
JSONObject root = new JSONObject();
JSONObject head = new JSONObject();
root.put("head", head);
createVariables(queryResult.getResultVars(), head);
JSONObject results = new JSONObject();
root.put("results", results);
JSONArray bindings = null;
while (queryResult.hasNext()) {
if (bindings == null) {
bindings = new JSONArray();
results.put("bindings", bindings);
}
bindings.add(createResult(queryResult.next()));
}
return root;
}
/**
* Helper: creates value element from {@link Resource} depending on its
* class
*
*/
private JSONObject createResultElement(Resource resource) {
JSONObject element = new JSONObject();
if (resource instanceof UriRef) {
element.put("type", "uri");
element.put("value", UriRef.class.cast(resource).getUnicodeString());
} else if (resource instanceof PlainLiteral) {
element.put("type", "literal");
element.put("value", PlainLiteral.class.cast(resource).getLexicalForm());
Language lang = PlainLiteral.class.cast(resource).getLanguage();
if (lang != null) {
element.put("xml:lang", lang.toString());
}
} else if (resource instanceof TypedLiteral) {
element.put("type", "typed-literal");
element.put("datatype", TypedLiteral.class.cast(resource).getDataType().getUnicodeString());
element.put("value", TypedLiteral.class.cast(resource).getLexicalForm());
} else if (resource instanceof BNode) {
element.put("type", "bnode");
element.put("value", "/");
} else {
element = null;
}
return element;
}
/**
* Helper: creates results element from ResultSet
*
*/
private JSONObject createResult(SolutionMapping solutionMap) {
JSONObject result = new JSONObject();
Set<Variable> keys = solutionMap.keySet();
for (Variable key : keys) {
result.put(key.getName(), createResultElement((Resource) solutionMap.get(key)));
}
return result;
}
private void createVariables(List<String> variables, JSONObject head) {
JSONArray vars = null;
for (String variable : variables) {
if (vars == null) {
vars = new JSONArray();
head.put("vars", vars);
}
vars.add(variable);
}
}
}