30.3 Neo4j

Neo4j is an open-source NoSQL graph database that uses a rich data model of nodes related by first class relationships which is better suited for connected big data than traditional rdbms approaches. Spring Boot offers several conveniences for working with Neo4j, including the spring-boot-starter-data-neo4j ‘Starter’.

30.3.1 Connecting to a Neo4j database

You can inject an auto-configured Neo4jSession, Session or Neo4jOperations instance as you would any other Spring Bean. By default the instance will attempt to connect to a Neo4j server using localhost:7474:

_@Component_
public class MyBean {

    private final Neo4jTemplate neo4jTemplate;

    _@Autowired_
    public MyBean(Neo4jTemplate neo4jTemplate) {
        this.neo4jTemplate = neo4jTemplate;
    }

    // ...

}

You can take full control of the configuration by adding a org.neo4j.ogm.config.Configuration @Bean of your own. Also, adding a @Bean of type Neo4jOperations disables the auto-configuration.

You can configure the user and credentials to use via the spring.data.neo4j.* properties:

spring.data.neo4j.uri=http://my-server:7474
spring.data.neo4j.username=neo4j
spring.data.neo4j.password=secret

30.3.2 Using the embedded mode

	Note
Neo4j’s embedded mode is subject to a different licensing, make sure to review it before integrating the dependency in your application.

If you add org.neo4j:neo4j-ogm-embedded-driver to the dependencies of your application, Spring Boot will automatically configure an in-process embedded instance of Neo4j that will not persist any data when your application shuts down. You can explicitly disable that mode using spring.data.neo4j.embedded.enabled=false. You can also enable persistence for the embedded mode:

    spring.data.neo4j.uri=file://var/tmp/graph.db

30.3.3 Neo4jSession

By default, the lifetime of the session is scope to the application. If you are running a web application you can change it to scope or request easily:

    spring.data.neo4j.session.scope=session

30.3.4 Spring Data Neo4j repositories

Spring Data includes repository support for Neo4j.

In fact, both Spring Data JPA and Spring Data Neo4j share the same common infrastructure; so you could take the JPA example from earlier and, assuming that City is now a Neo4j OGM @NodeEntity rather than a JPA @Entity, it will work in the same way.

	Tip
You can customize entity scanning locations using the @EntityScan annotation.

To enable repository support (and optionally support for @Transactional), add the following two annotations to your Spring configuration:

_@EnableNeo4jRepositories(basePackages = "com.example.myapp.repository")_
@EnableTransactionManagement

30.3.5 Repository example

package com.example.myapp.domain;

import org.springframework.data.domain.*;
import org.springframework.data.repository.*;

public interface CityRepository extends GraphRepository<City> {

    Page<City> findAll(Pageable pageable);

    City findByNameAndCountry(String name, String country);

}

	Tip
For complete details of Spring Data Neo4j, including its rich object mapping technologies, refer to their reference documentation.