Chapter 4. The power of traversals
This chapter covers
- Querying Neo4j using the Core Java API
- Traversing nodes and relationships using the Neo4j Traversal API
- Extending and customizing built-in Neo4j traversal operations
Chapter 3 introduced you to the Neo4j Core Java API and you created a graph representing a social network of users and the movies they like. In this chapter we’re going to look at graph traversals—a powerful way of querying the graph data. Graph traversal is the process of visiting nodes in the graph by following the relationships between nodes in a particular manner.
We’ll demonstrate the traversal options by showing you how to solve simple traversal problems, followed by more complex ones. In this chapter you’ll get more familiar with the Neo4j Core Java API, as well as with the more advanced Neo4j Traversal Framework Java API (or “Neo4j Traversal API” for short).
Let’s start with the simplest traversal, which follows relationships to find direct neighbors of the starting node using the Neo4j Core Java API.
The first traversal approach we’ll look at makes use of standard methods available on the Neo4j Core Java API. We’ll use the graph created in chapter 3 to perform the traversals.
The first traversal we’ll look at can be described as “Starting from the node representing the user John Johnson, find all the movies that this user has seen.” Figure 4.1 illustrates the part of the graph we’re interested in.