Chapter 24. Neo4jTemplate

The Neo4jTemplate offers the convenient API of Spring templates for the Neo4j graph database.

24.1. Basic operations

For direct retrieval of nodes and relationships, the getReferenceNode(), getNode() and getRelationship() methods can be used.

There are methods (createNode() and createRelationship()) for creating nodes and relationships that automatically set provided properties and optionally index certain fields.

Example 24.1. Neo4j template

import static org.springframework.data.graph.core.Property._;

Neo4jOperations neo = new Neo4jTemplate(graphDatabaseService);

Node michael = neo.createNode(_("name","Michael"));
Node mark = neo.createNode(_("name","Mark"));
Node thomas = neo.createNode(_("name","Thomas"));

neo.createRelationship(mark,thomas, WORKS_WITH, _("project","spring-data"));

neo.index("devs",thomas, "name","Thomas");

assert "Mark".equals(neo.query("devs","name","Mark",new NodeNamePathMapper()));

24.2. Indexing

Adding nodes and relationships to an index is done with the index() method.

The query() methods either take a field/value combination to look for exact matches in the index, or a Lucene query object or string to handle more complex queries. All query() methods provide Path results to a PathMapper.

24.3. Graph traversal

The traversal methods are at the core of graph operations. As such, they are fully supported in the Neo4jTemplate. The traverseNext() method traverses to the direct neighbors of the start node, filtering the relationships according to the parameters.

The traverse() method covers the full traversal operation that takes a TraversalDescription (typically built with the Traversal.description() DSL) and runs it from the start node. Each path that is returned by the traversal is passed to the PathMapper to be converted into the desired type.

24.4. Path abstraction and PathMapper

For the querying operations Neo4jTemplate unifies the result with the Path abstraction that comes from Neo4j. Much like a result set, a path contains a chain of nodes() connected by relationships(), starting at a startNode() and ending at a endNode(). The lastRelationship() is also available separately. The Path abstraction also wraps results that contain just nodes or relationships.

Using implementations of PathMapper<T> and PathMapper.WithoutResult (comparable with RowMapper and RowCallbackHandler), the paths can be converted to arbitrary Java objects.

With EntityPath and EntityMapper there is also support for using node entities within the Path and PathMapper constructs.

24.5. Transactions

The Neo4jTemplate provides configurable implicit transactions for all its methods. By default it creates a transaction for each call (which is a no-op if there is already a transaction running). If you call the constructor with the useExplicitTransactions parameter set to true, it won't create any transactions so you have to provide them using @Transactional or the TransactionTemplate.