Spring Data Neo4j Agent Skill

Spring Data Neo4j Integration Patterns

Overview

Provides Spring Data Neo4j integration patterns for Spring Boot applications. Covers node entity mapping with @Node and @Relationship, repository configuration (imperative and reactive), custom Cypher queries with @Query, and integration testing with embedded Neo4j databases.

When to Use

Use this skill when working with:

• Graph databases and Neo4j integration in Spring Boot
• Node entities, relationships, and Cypher queries
• Spring Data Neo4j repositories (imperative or reactive)
• Neo4j testing with embedded databases

Instructions

1. Set Up Spring Data Neo4j

Add the dependency:

Maven:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-neo4j</artifactId>
</dependency>

Gradle:

implementation 'org.springframework.boot:spring-boot-starter-data-neo4j'

Configure connection in application.properties:

spring.neo4j.uri=bolt://localhost:7687
spring.neo4j.authentication.username=neo4j
spring.neo4j.authentication.password=secret

Configure Cypher-DSL dialect (recommended):

@Configuration
public class Neo4jConfig {
    @Bean
    Configuration cypherDslConfiguration() {
        return Configuration.newConfig()
            .withDialect(Dialect.NEO4J_5).build();
    }
}

> Validation Checkpoint: Run MATCH (n) RETURN count(n) via cypher-shell to verify the connection works before proceeding.

2. Define Node Entities

• Use @Node annotation to mark entity classes
• Choose ID strategy:
• Business key as @Id (immutable, natural identifier)
• Generated @Id @GeneratedValue (Neo4j internal ID)
• Define relationships with @Relationship annotation
• Keep entities immutable with final fields
• Use @Property for custom property names

> Validation Checkpoint: If entity save fails, check for constraint violations—duplicate IDs violate uniqueness constraints.

3. Create Repositories

• Extend repository interface:
• Neo4jRepository<Entity, ID> for imperative operations
• ReactiveNeo4jRepository<Entity, ID> for reactive operations
• Use query derivation for simple queries
• Apply @Query annotation for complex Cypher queries
• Use $paramName syntax for parameters

> Validation Checkpoint: Test repository with findAll() first—if empty, verify the Neo4j instance is running and credentials are correct.

4. Test Your Implementation

• Use @DataNeo4jTest for repository testing with test slicing
• Set up Neo4j Harness with embedded database and fixtures
• Provide test data via withFixture() Cypher queries
• Clean up test data between tests

> Validation Checkpoint: If tests fail with "Connection refused", ensure the embedded Neo4j started successfully in @BeforeAll.

Basic Entity Mapping

Node Entity with Business Key

@Node("Movie")
public class MovieEntity {

    @Id
    private final String title;  // Business key as ID

    @Property("tagline")
    private final String description;

    private final Integer year;

    @Relationship(type = "ACTED_IN", direction = Direction.INCOMING)
    private List<Roles> actorsAndRoles = new ArrayList<>();

    @Relationship(type = "DIRECTED", direction = Direction.INCOMING)
    private List<PersonEntity> directors = new ArrayList<>();

    public MovieEntity(String title, String description, Integer year) {
        this.title = title;
        this.description = description;
        this.year = year;
    }
}

Node Entity with Generated ID

@Node("Movie")
public class MovieEntity {

    @Id @GeneratedValue
    private Long id;

    private final String title;

    @Property("tagline")
    private final String description;

    public MovieEntity(String title, String description) {
        this.id = null;  // Never set manually
        this.title = title;
        this.description = description;
    }

    // Wither method for immutability with generated IDs
    public MovieEntity withId(Long id) {
        if (this.id != null && this.id.equals(id)) {
            return this;
        } else {
            MovieEntity newObject = new MovieEntity(this.title, this.description);
            newObject.id = id;
            return newObject;
        }
    }
}

Repository Patterns

Basic Repository Interface

@Repository
public interface MovieRepository extends Neo4jRepository<MovieEntity, String> {

    // Query derivation from method name
    MovieEntity findOneByTitle(String title);

    List<MovieEntity> findAllByYear(Integer year);

    List<MovieEntity> findByYearBetween(Integer startYear, Integer endYear);
}

Reactive Repository

@Repository
public interface MovieRepository extends ReactiveNeo4jRepository<MovieEntity, String> {

    Mono<MovieEntity> findOneByTitle(String title);

    Flux<MovieEntity> findAllByYear(Integer year);
}

Imperative vs Reactive:

• Use Neo4jRepository for blocking, imperative operations
• Use ReactiveNeo4jRepository for non-blocking, reactive operations
• Do not mix imperative and reactive in the same application
• Reactive requires Neo4j 4+ on the database side

Custom Queries with @Query

@Repository
public interface AuthorRepository extends Neo4jRepository<Author, Long> {

    @Query("MATCH (b:Book)-[:WRITTEN_BY]->(a:Author) " +
           "WHERE a.name = $name AND b.year > $year " +
           "RETURN b")
    List<Book> findBooksAfterYear(@Param("name") String name,
                                   @Param("year") Integer year);

    @Query("MATCH (b:Book)-[:WRITTEN_BY]->(a:Author) " +
           "WHERE a.name = $name " +
           "RETURN b ORDER BY b.year DESC")
    List<Book> findBooksByAuthorOrderByYearDesc(@Param("name") String name);
}

Custom Query Best Practices:

• Use $parameterName for parameter placeholders
• Use @Param annotation when parameter name differs from method parameter
• MATCH specifies node patterns and relationships
• WHERE filters results
• RETURN defines what to return

Testing Strategies

Neo4j Harness for Integration Testing

Test Configuration:

@DataNeo4jTest
class BookRepositoryIntegrationTest {

    private static Neo4j embeddedServer;

    @BeforeAll
    static void initializeNeo4j() {
        embeddedServer = Neo4jBuilders.newInProcessBuilder()
            .withDisabledServer()  // No HTTP access needed
            .withFixture(
                "CREATE (b:Book {isbn: '978-0547928210', " +
                "name: 'The Fellowship of the Ring', year: 1954})" +
                "-[:WRITTEN_BY]->(a:Author {id: 1, name: 'J. R. R. Tolkien'}) " +
                "CREATE (b2:Book {isbn: '978-0547928203', " +
                "name: 'The Two Towers', year: 1956})" +
                "-[:WRITTEN_BY]->(a)"
            )
            .build();
    }

    @AfterAll
    static void stopNeo4j() {
        embeddedServer.close();
    }

    @DynamicPropertySource
    static void neo4jProperties(DynamicPropertyRegistry registry) {
        registry.add("spring.neo4j.uri", embeddedServer::boltURI);
        registry.add("spring.neo4j.authentication.username", () -> "neo4j");
        registry.add("spring.neo4j.authentication.password", () -> "null");
    }

    @Autowired
    private BookRepository bookRepository;

    @Test
    void givenBookExists_whenFindOneByTitle_thenBookIsReturned() {
        Book book = bookRepository.findOneByTitle("The Fellowship of the Ring");
        assertThat(book.getIsbn()).isEqualTo("978-0547928210");
    }
}

Examples

Example 1: Saving and Retrieving Entities

Input:

MovieEntity movie = new MovieEntity("The Matrix", "Welcome to the Real World", 1999);
movieRepository.save(movie);

MovieEntity found = movieRepository.findOneByTitle("The Matrix");

Output:

MovieEntity{
    title="The Matrix",
    description="Welcome to the Real World",
    year=1999,
    actorsAndRoles=[],
    directors=[]
}

Example 2: Custom Cypher Query

Input:

List<Book> books = authorRepository.findBooksAfterYear("J.R.R. Tolkien", 1950);

Output:

[
    Book{isbn="978-0547928210", name="The Fellowship of the Ring", year=1954},
    Book{isbn="978-0547928203", name="The Two Towers", year=1956},
    Book{isbn="978-0547928227", name="The Return of the King", year=1957}
]

Example 3: Relationship Traversal

Input:

@Query("MATCH (m:Movie)<-[:ACTED_IN]-(a:Person) " +
       "WHERE m.title = $title RETURN a.name as actorName")
List<String> findActorsByMovieTitle(@Param("title") String title);

List<String> actors = movieRepository.findActorsByMovieTitle("The Matrix");

Output:

["Keanu Reeves", "Laurence Fishburne", "Carrie-Anne Moss", "Hugo Weaving"]

Progress from basic to advanced examples covering complete movie database, social network patterns, e-commerce product catalogs, custom queries, and reactive operations.

See examples for comprehensive code examples.

Best Practices

Entity Design

• Use immutable entities with final fields
• Choose between business keys (@Id) or generated IDs (@Id @GeneratedValue)
• Keep entities focused on graph structure, not business logic
• Use proper relationship directions (INCOMING, OUTGOING, UNDIRECTED)

Repository Design

• Extend Neo4jRepository for imperative or ReactiveNeo4jRepository for reactive
• Use query derivation for simple queries
• Write custom @Query for complex graph patterns
• Don't mix imperative and reactive in same application

Configuration

• Always configure Cypher-DSL dialect explicitly
• Use environment-specific properties for credentials
• Never hardcode credentials in source code
• Configure connection pooling based on load

Testing

• Use Neo4j Harness for integration tests
• Provide test data via withFixture() Cypher queries
• Use @DataNeo4jTest for test slicing
• Test both successful and edge-case scenarios

Architecture

• Use constructor injection exclusively
• Separate domain entities from DTOs
• Follow feature-based package structure
• Keep domain layer framework-agnostic

Security

• Use Spring Boot property overrides for credentials
• Configure proper authentication and authorization
• Validate input parameters in service layer
• Use parameterized queries to prevent Cypher injection

Constraints and Warnings

• Do not mix imperative and reactive repositories in the same application.
• Neo4j transactions are required for write operations; ensure @Transactional is properly configured.
• Be cautious with deep relationship traversal as it can cause performance issues.
• Large result sets should be paginated to avoid memory problems.
• Cypher queries are case-sensitive; ensure consistent casing in property names.
• Immutable entities require proper wither methods for generated IDs.
• Relationships in Spring Data Neo4j are not lazy-loaded by default; consider projection for large graphs.
• The Neo4j Java driver is not compatible with reactive streams; use the reactive driver for reactive operations.

Troubleshooting

| Problem | Cause | Solution |

|---------|-------|----------|

| Connection refused on localhost:7687 | Neo4j server not running | Start Neo4j or use embedded Neo4j for tests |

| Authentication failed | Wrong credentials | Check spring.neo4j.authentication.username/password |

| Entity not saved / MATCH returns nothing | Transaction not committed | Add @Transactional or verify auto-commit settings |

| ConstraintViolationException on save | Duplicate @Id value | Ensure IDs are unique or use @GeneratedValue |

| Relationships missing in results | Wrong @Relationship direction | Check Direction.INCOMING/OUTGOING/UNDIRECTED |

| @Query returns wrong data | Cypher parameter syntax | Use $paramName not $ {paramName} |

| Test fails with @DataNeo4jTest | Embedded Neo4j not started | Ensure @BeforeAll starts Neo4j before tests |

References

For detailed documentation including complete API reference, Cypher query patterns, and configuration options:

• Annotations Reference
• Cypher Query Language
• Configuration Properties
• Repository Methods
• Projections and DTOs
• Transaction Management
• Performance Tuning

External Resources

• Spring Data Neo4j Official Documentation
• Neo4j Developer Guide
• Spring Data Commons Documentation