Reputation: 633
the topic pretty much says it: I want to create a relationship with a type between two nodes. Pretty straight forward, one might think. But like so often in the last weeks, I struggle with the correct syntax.
What I'm doing right now is this:
public URI createRelationship(GraphNodeTypes sourceType, URI sourceNode,
GraphNodeTypes targetType, URI targetNode,
GraphRelationshipTypes relationshipType, String[] jsonAttributes) {
URI relationShipLocation = null;
String cypherArt = getNodeIdFromLocation(sourceNode)+"-[:"+relationshipType+"]->"+getNodeIdFromLocation(targetNode);
logger.info("creating relationship ({}:{}) -[:{}]-> ({}:{})",
sourceType,
getNodeIdFromLocation(sourceNode),
relationshipType,
targetType,
getNodeIdFromLocation(targetNode));
try {
URI finalUrl = new URI( sourceNode.toString() + "/relationships" );
String cypherStatement = generateJsonRelationship( targetNode,
relationshipType,
jsonAttributes );
logger.trace("sending CREATE RELATIONSHIP cypher as {} to endpoint {}", cypherStatement, finalUrl);
WebResource resource = Client.create().resource( finalUrl );
ClientResponse response = resource
.accept( MediaType.APPLICATION_JSON )
.type( MediaType.APPLICATION_JSON )
.entity( cypherStatement )
.post( ClientResponse.class );
String responseEntity = response.getEntity(String.class).toString();
int responseStatus = response.getStatus();
logger.trace("POST to {} returned status code {}, returned data: {}",
finalUrl, responseStatus,
responseEntity);
// first check if the http code was ok
HttpStatusCodes httpStatusCodes = HttpStatusCodes.getHttpStatusCode(responseStatus);
if (!httpStatusCodes.isOk()){
if (httpStatusCodes == HttpStatusCodes.FORBIDDEN){
logger.error(HttpErrorMessages.getHttpErrorText(httpStatusCodes.getErrorCode()));
} else {
logger.error("Error {} sending data to {}: {} ", response.getStatus(), finalUrl, HttpErrorMessages.getHttpErrorText(httpStatusCodes.getErrorCode()));
}
} else {
JSONParser reponseParser = new JSONParser();
Object responseObj = reponseParser.parse(responseEntity);
JSONObject jsonResponseObj = responseObj instanceof JSONObject ?(JSONObject) responseObj : null;
if(jsonResponseObj == null)
throw new ParseException(0, "returned json object is null");
//logger.trace("returned response object is {}", jsonResponseObj.toString());
try {
relationShipLocation = new URI((String)((JSONObject)((JSONArray)((JSONObject)((JSONArray)((JSONObject)((JSONArray)jsonResponseObj.get("results")).get(0)).get("data")).get(0)).get("rest")).get(0)).get("self"));
} catch (Exception e) {
logger.warn("CREATE RELATIONSHIP statement did not return a self object, returning null -- error was {}", e.getMessage());
relationShipLocation = null;
}
}
} catch (Exception e) {
logger.error("could not create relationship ");
}
return relationShipLocation;
}
private static String generateJsonRelationship( URI endNode,
GraphRelationshipTypes relationshipType, String[] jsonAttributes ) {
StringBuilder sb = new StringBuilder();
sb.append( "{ \"to\" : \"" );
sb.append( endNode.toString() );
sb.append( "\", " );
sb.append( "\"type\" : \"" );
sb.append( relationshipType.toString() );
if ( jsonAttributes == null || jsonAttributes.length < 1 ){
sb.append( "\"" );
} else {
sb.append( "\", \"data\" : " );
for ( int i = 0; i < jsonAttributes.length; i++ ) {
sb.append( jsonAttributes[i] );
if ( i < jsonAttributes.length - 1 ){
// Miss off the final comma
sb.append( ", " );
}
}
}
sb.append( " }" );
return sb.toString();
}
But as you can guess, it's not working. I get this error in my application log:
INFO Neo4JPersistence - creating relationship (POST:101) -[:BELONGS_TO]-> (SOCIALNETWORK:72)
TRACE Neo4JPersistence - sending CREATE RELATIONSHIP cypher as { "to" : "http://localhost:7474/db/data/node/72", "type" : "BELONGS_TO" } to endpoint http://localhost:7474/db/data/node/101/relationships
The neo4j server log outputs this:
11:15:57.278 [qtp683244938-387] WARN o.e.jetty.servlet.ServletHandler - /db/data/node/101/relationships
org.neo4j.graphdb.NotFoundException: Node 101 not found
BUT this node is created, successfully just some milliseconds before - I can see it in the neo4j browser.
(NEO4J) -[:LOST]-> (ME)
Chris
Upvotes: 0
Views: 122
Reputation: 633
I found the problem.
For all beginners like me, that might stumble upon it: If you want to create a relationship between two nodes created within a transaction, you have to commit the transaction, BEFORE creating the relationship!
Greetings,
Chris
Upvotes: 1