如何在Neo4j中找到匹配关系模式的节点列表？

Question

I have to find all nodes, x1 x2 x3 such that x1-[:R1]->x2-[:R2]->x3 .

Here R1 and R2 will be known aforehand, and we have to find all such x1 x2 x3 which match the condition. Also, the number of relationships may increase or decrease ie there could be three relationship R1 R2 R3 and it should return all x1 x2 x3 x4 which satisfies the condition.

I need to do this using Java API and not Cypher queries.

I found the classes PatternNode and PatternRelationship, but found it hard to understand and how to construct them in order to achieve what I want to achieve. Also both the classes are deprecated. Is there a way I could achieve this through Java?

Answer 1

You have a couple of ways to traverse a graph in java. These are your options:

Execute a Cypher query

Use the ExecutionEngine to execute a Cypher Query:

final ExecutionEngine engine = new ExecutionEngine(graphDB);
ExecutionResult result = engine.execute("YOUR_CYPHER_QUERY");

Use the Cypher DSL syntax

Again, you're basically writing a Cypher query, but this time, your using a nice DSL statement. Check out https://github.com/neo4j/cypher-dsl .

Execute q = start(node("john", john)).
            match(path().from("john").out("friend").link().out("friend").to("fof")).
            returns(properties("john.name", "fof.name"));
ExecutionResult result = engine.execute( q.toString() ).toString();

Use the traversal API

You control the complete graph traversal. An example:

for (final Path position : Traversal.description().depthFirst()
    .relationships(RelationType.RELATIONSHIP_TYPE, Direction.INCOMING).traverse(node)) {
   System.out.println(position.endNode();
}

It's up to you, but I'd prefer a simple Cypher statement.