GraphMLEdge convertedEdge = new GraphMLEdge(); GraphMLGraph sourceGraph = nodeIdToGraphMapping.get(eachEdge.getSource()); GraphMLGraph targetGraph = nodeIdToGraphMapping.get(eachEdge.getTarget()); throw new InvalidGraphException("No graph found for edge with id " + eachEdge.getSource()); GraphMLNode sourceNode = sourceGraph.getNodeById(eachEdge.getSource()); GraphMLNode targetNode = targetGraph.getNodeById(eachEdge.getTarget());