Java tutorial
/** * This file is part of d:swarm graph extension. * * d:swarm graph extension is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * d:swarm graph extension is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with d:swarm graph extension. If not, see <http://www.gnu.org/licenses/>. */ package org.dswarm.graph.resources; import java.io.BufferedOutputStream; import java.io.IOException; import java.io.OutputStream; import javax.ws.rs.Consumes; import javax.ws.rs.GET; import javax.ws.rs.POST; import javax.ws.rs.Path; 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.Response; import javax.ws.rs.core.StreamingOutput; import javax.xml.stream.XMLStreamException; import javax.xml.stream.XMLStreamWriter; import com.fasterxml.jackson.databind.JsonNode; import com.fasterxml.jackson.databind.ObjectMapper; import com.fasterxml.jackson.databind.node.ObjectNode; import com.google.common.base.Optional; import org.neo4j.graphdb.GraphDatabaseService; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.dswarm.common.DMPStatics; import org.dswarm.common.model.AttributePath; import org.dswarm.common.model.util.AttributePathUtil; import org.dswarm.graph.DMPGraphException; import org.dswarm.graph.index.NamespaceIndex; import org.dswarm.graph.tx.Neo4jTransactionHandler; import org.dswarm.graph.tx.TransactionHandler; import org.dswarm.graph.xml.read.PropertyGraphXMLReader; import org.dswarm.graph.xml.read.XMLReader; /** * TODO: refactor the design of the resources. this is not RESTy atm, i.e., there should be one pattern how the receive a certain * data model from this unmanaged extension and depending on the Accept-Type of the request the result will be in this format * (media type), i.e., "gdm", various RDF serialisation, XML, or whatever ... => i.e., we don't need separate resources * (endpoints) for certain descriptions (abstract formats) or representations (concrete formats, mediatypes, serialisations) * * @author tgaengler */ @Path("/xml") public class XMLResource { private static final Logger LOG = LoggerFactory.getLogger(XMLResource.class); /** * The object mapper that can be utilised to de-/serialise JSON nodes. */ private final ObjectMapper objectMapper; public XMLResource() { objectMapper = new ObjectMapper(); } @GET @Path("/ping") public String ping() { XMLResource.LOG.debug("ping was called"); return "pong"; } @POST @Path("/get") @Consumes(MediaType.APPLICATION_JSON) @Produces(MediaType.APPLICATION_XML) public Response readXML(final String jsonObjectString, @Context final GraphDatabaseService database) throws DMPGraphException { XMLResource.LOG.debug("try to read XML records from graph db"); final ObjectNode json; try { json = objectMapper.readValue(jsonObjectString, ObjectNode.class); } catch (final IOException e) { final String message = "could not deserialise request JSON for read from graph DB request"; XMLResource.LOG.debug(message); throw new DMPGraphException(message, e); } final String recordClassUri = json.get(DMPStatics.RECORD_CLASS_URI_IDENTIFIER).asText(); final String dataModelUri = json.get(DMPStatics.DATA_MODEL_URI_IDENTIFIER).asText(); final JsonNode rootAttributePathNode = json.get(DMPStatics.ROOT_ATTRIBUTE_PATH_IDENTIFIER); final Optional<AttributePath> optionalRootAttributePath = Optional .fromNullable(AttributePathUtil.parseAttributePathNode(rootAttributePathNode)); final Optional<String> optionalRecordTag; final JsonNode recordTagNode = json.get(DMPStatics.RECORD_TAG_IDENTIFIER); if (recordTagNode != null) { optionalRecordTag = Optional.fromNullable(recordTagNode.asText()); } else { optionalRecordTag = Optional.absent(); } final JsonNode versionNode = json.get(DMPStatics.VERSION_IDENTIFIER); final Optional<Integer> optionalVersion; if (versionNode != null) { optionalVersion = Optional.fromNullable(versionNode.asInt()); } else { optionalVersion = Optional.absent(); } final JsonNode allVersionsNode = json.get(DMPStatics.ALL_VERSIONS_IDENTIFIER); final Optional<Boolean> optionalAllversion; if (allVersionsNode != null) { optionalAllversion = Optional.fromNullable(allVersionsNode.asBoolean()); } else { optionalAllversion = Optional.absent(); } final Optional<JsonNode> optionalOriginalDataTypeNode = Optional .fromNullable(json.get(DMPStatics.ORIGINAL_DATA_TYPE_IDENTIFIER)); final Optional<String> optionalOriginalDataType; if (optionalOriginalDataTypeNode.isPresent()) { final Optional<String> optionalOriginalDataTypeFromJSON = Optional .fromNullable(optionalOriginalDataTypeNode.get().asText()); if (optionalOriginalDataTypeFromJSON.isPresent()) { optionalOriginalDataType = optionalOriginalDataTypeFromJSON; } else { optionalOriginalDataType = Optional.absent(); } } else { optionalOriginalDataType = Optional.absent(); } LOG.debug("try to read XML records for data model uri = '{}' and record class uri = '{}' from graph db", dataModelUri, recordClassUri); final TransactionHandler tx = new Neo4jTransactionHandler(database); final NamespaceIndex namespaceIndex = new NamespaceIndex(database, tx); final XMLReader xmlReader = new PropertyGraphXMLReader(optionalRootAttributePath, optionalRecordTag, recordClassUri, dataModelUri, optionalVersion, optionalAllversion, optionalOriginalDataType, database, tx, namespaceIndex); final StreamingOutput stream = new StreamingOutput() { @Override public void write(final OutputStream os) throws IOException, WebApplicationException { try { final BufferedOutputStream bos = new BufferedOutputStream(os, 1024); final Optional<XMLStreamWriter> optionalWriter = xmlReader.read(bos); if (optionalWriter.isPresent()) { optionalWriter.get().flush(); optionalWriter.get().close(); LOG.debug( "finished reading '{}' XML records for data model uri = '{}' and record class uri = '{}' from graph db", xmlReader.recordCount(), dataModelUri, recordClassUri); } else { bos.close(); os.close(); LOG.debug( "couldn't find any XML records for data model uri = '{}' and record class uri = '{}' from graph db", dataModelUri, recordClassUri); } } catch (final DMPGraphException | XMLStreamException e) { throw new WebApplicationException(e); } } }; return Response.ok(stream, MediaType.APPLICATION_XML_TYPE).build(); } }