Spring Data Neo4j Rx
The post focused on the Spring Data Neo4j RX, which was maintained by Neo4j team. Currently this project is discontinued, the effort is merged into the official Spring Data Neo4j project, read this doc to update yourself.
Generate a Spring Boot WebFlux project using Spring Initializr.
Do not add Spring Data Neo4j into the dependencies, we will use Spring Data Neo4j Rx instead.
Open the pom.xml file in the project root folder, add the Spring Data Neo4j RX dependency manually.
<dependency>
<groupId>org.neo4j.springframework.data</groupId>
<artifactId>spring-data-neo4j-rx-spring-boot-starter</artifactId>
<version>${spring-data-neo4j-rx.version}</version>
</dependency>
Declare the property spring-data-neo4j-rx.version in pom.xml.
<spring-data-neo4j-rx.version>1.0.0-beta03</spring-data-neo4j-rx.version>
Create a POJO class for presenting a node in Neo4j graph.
@Node
@Data
@ToString
@Builder
@NoArgsConstructor
@AllArgsConstructor
class Post {
@Id
@GeneratedValue
private Long id;
private String title;
private String content;
@CreatedDate
private LocalDateTime createdDate;
}
In the above codes, @Node, @Id, @GeneratedValue are located in the package org.neo4j.springframework.data.core.schema which is part of the new Spring Data Neo4j Rx project.
Spring Data Neo4j Rx also supports the annotations from Spring Data Commons project. For example, you can use Id and Persistent from Spring Data Commons instead of the Id and Node annotations from the Spring Data Neo4j Rx.
Spring Data Neo4j Rx supports data auditing as well, so you can use @CreatedDate, @CreatedBy, @LastModifiedDate, @LastModifiedBy as usual, just add @EnableNeo4jAuditing on the application class to enable it. Unfortunately, there is no AuditorAware reactive variant available in SDN RX, thus it can not fill CreatedBy and lastModifiedBy automatically.
Create a Repository for the Post entity.
interface PostRepository extends ReactiveNeo4jRepository<Post, Long> {
}
Create a Controller to expose CRUD RESTful APIs.
@RestController()
@RequestMapping(value = "/posts")
@RequiredArgsConstructor
class PostController {
private final PostRepository posts;
@GetMapping("")
public Flux<Post> all() {
return this.posts.findAll();
}
@PostMapping("")
public Mono<Post> create(@RequestBody Post post) {
return this.posts.save(post);
}
@GetMapping("/{id}")
public Mono<Post> get(@PathVariable("id") Long id) {
return Mono.just(id)
.flatMap(posts::findById)
.switchIfEmpty(Mono.error(new PostNotFoundException(id)));
}
@PutMapping("/{id}")
public Mono<Post> update(@PathVariable("id") Long id, @RequestBody Post post) {
return this.posts.findById(id)
.map(p -> {
p.setTitle(post.getTitle());
p.setContent(post.getContent());
return p;
})
.flatMap(this.posts::save);
}
@DeleteMapping("/{id}")
public Mono<Void> delete(@PathVariable("id") Long id) {
return this.posts.deleteById(id);
}
}
The usage of controllers is similar to Spring WebMVC, and you can also use RestControllerAdvice to handle the exceptions.
For example, in the get method, if the Post is not found, throw an exception PostNotFoundException in the reactive flow by Mono.error.
class PostNotFoundException extends RuntimeException {
PostNotFoundException(Long id) {
super("Post #" + id + " was not found");
}
}
When the PostNotFoundException is caught, send a 404 Not Found status code to the client.
@RestControllerAdvice
@Slf4j
class RestExceptionHandler {
@ExceptionHandler(PostNotFoundException.class)
ResponseEntity postNotFound(PostNotFoundException ex) {
log.debug("handling exception::" + ex);
return ResponseEntity.notFound().build();
}
}
Almost done. Let’s try to initialize some sample data for demo purpose.
Create a CommandLineRunner bean to insert some data.
@Component
@Slf4j
@RequiredArgsConstructor
class DataInitializer implements CommandLineRunner {
private final PostRepository posts;
private final ReactiveNeo4jClient client;
@Override
public void run(String[] args) {
log.info("start data initialization ...");
this.posts
.deleteAll()
.thenMany(
Flux
.just("Post one", "Post two")
.flatMap(
title -> this.posts.save(Post.builder().title(title).content("content of " + title).build())
)
)
.log()
.then()
.doOnNext(
(v) -> client
.query("MATCH (p:Post) RETURN p")
.fetchAs(Post.class)
.mappedBy((t, r) -> (Post) (r.get("p").asObject()))
.all()
.subscribe(System.out::println)
)
.subscribe(
null,
null,
() -> log.info("done initialization...")
);
}
}
Configure the Neo4j driver properties in application.properties file.
org.neo4j.driver.uri=bolt://localhost:7687
org.neo4j.driver.authentication.username=neo4j
org.neo4j.driver.authentication.password=test
Note: SDN Rx uses a different namespace
org.neo4j.driver.
Before running this application, it requires a running Neo4j server.
The following code fragment is a docker-compose configuration which allow you run Neo4j server in docker containers.
neo4j:
image: neo4j:4
environment:
- "NEO4J_AUTH=neo4j/test" # user none as value to disable auth setting
# - "NEO4J_ACCEPT_LICENSE_AGREEMENT=yes" # only neede by enterprise version
ports:
- 7687:7687
- 7474:7474
Run the following command to start a local Neo4j server in Docker container.
docker-compose up neo4j
Now start up our application, when it is ready, use curl to test the APIs.
# Get all posts
curl http://localhost:8080/posts
[{"id":0,"title":"Post one","content":"content of Post one","createdDate":null},{"id":1,"title":"Post two","content":"content of Post two","createdDate":null}]
# Get post by id
curl http://localhost:8080/posts/0
{"id":0,"title":"Post one","content":"content of Post one","createdDate":null}
# Get none exsting post
curl -v http://localhost:8080/posts/10
* Trying ::1...
* TCP_NODELAY set
* Connected to localhost (::1) port 8080 (#0)
> GET /posts/10 HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.55.1
> Accept: */*
>
< HTTP/1.1 404 Not Found
< content-length: 0
<
* Connection #0 to host localhost left intact
Like Spring Data Mongo, SDN Rx also provides a @DataNeo4jTest annotation to provide test slice capability.
Add the following dependency into the project pom.xml.
<dependency>
<groupId>org.neo4j.springframework.data</groupId>
<artifactId>spring-data-neo4j-rx-spring-boot-test-autoconfigure</artifactId>
<version>${spring-data-neo4j-rx.version}</version>
<scope>test</scope>
</dependency>
Create a test class to the SDN Rx features.
@DataNeo4jTest
@Slf4j
public class PostRepositoryTest {
@Autowired
private PostRepository posts;
@BeforeEach
public void setup() throws IOException {
log.debug("running setup.....,");
this.posts.deleteAll()
.thenMany(testSaveMethod())
.log()
.thenMany(testFoundMethod())
.log()
.blockLast();// to make the tests work
// .subscribe(
// (data) -> log.info("found post:" + data),
// (err) -> log.error("" + err),
// () -> log.info("done")
// );
}
private Flux<Post> testSaveMethod() {
var data = Stream.of("Post one", "Post two")
.map(title -> Post.builder().title(title).content("The content of " + title).build())
.collect(Collectors.toList());
return Flux.fromIterable(data)
.flatMap(it -> this.posts.save(it));
}
private Flux<Post> testFoundMethod() {
return this.posts
.findAll(Example.of(Post.builder().title("Post one").build()));
}
@AfterEach
void teardown() {
//this.posts.deleteAll();
}
@Test
void testAllPosts() {
posts.findAll().sort(Comparator.comparing(post -> post.getTitle()))
.as(StepVerifier::create)
.consumeNextWith(p -> assertEquals("Post one", p.getTitle()))
.consumeNextWith(p -> assertEquals("Post two", p.getTitle()))
.verifyComplete();
}
}
But you have to run a Neo4j server to serve this test, currently SDN Rx does not provide an embedded Neo4j for test scope.
Get the complete codes, spring-reactive-sample/boot-data-neo4j-rx.
ReactiveNeo4jOperations
Beside Repository interface declaration, SDN Rx provides a ReactiveNeo4jOperations to access the data storage in a programmatic approach.
In Spring Boot projects, ReactiveNeo4jOperations bean is autoconfigured.
@Component
@RequiredArgsConstructor
class PostRepository {
private final ReactiveNeo4jOperations template;
public Mono<Long> count() {
return this.template.count(Post.class);
}
public Flux<Post> findAll() {
return this.template.findAll(Post.class);
}
public Flux<Post> findByTitleContains(String title) {
var postNode = node("Post").named("p");
return this.template.findAll(
match(postNode)
.where(postNode.property("title").contains(literalOf(title)))
.returning(postNode)
.build(),
Post.class
);
}
public Mono<Void> deleteById(Long id) {
return this.template.deleteById(id, Post.class);
}
public Mono<Post> save(Post post) {
return this.template.save(post);
}
public Mono<Post> findById(Long id) {
return this.template.findById(id, Post.class);
}
public Mono<Void> deleteAll() {
return this.template.deleteAll(Post.class);
}
}
For the complete codes, check spring-reactive-sample/boot-neo4j-rx.
ReactiveNeo4jClient
Benefit from the Spring Boot auto-configuration mechanism, a ReactiveNeo4jClient bean is ready for use. You can use it to interact with the Neo4j low level APIs, such as executing Cypher queries.
The following is a new version of PostRepository implemented by ReactiveNeo4jClient.
@Component
@RequiredArgsConstructor
class PostRepository {
private final ReactiveNeo4jClient client;
public Mono<Long> count() {
return client.query("MATCH (p:Post) RETURN count(p)")
.fetchAs(Long.class)
.mappedBy((ts, r) -> r.get(0).asLong())
.one();
}
public Flux<Post> findAll() {
return client
.query(
"MATCH (p:Post) " +
" RETURN p.id as id, p.title as title, p.content as content, p.createdAt as createdAt, p.updatedAt as updatedAt"
)
.fetchAs(Post.class).mappedBy((ts, r) ->
Post.builder()
.id(r.get("id").asString())
.title(
r.get("title").asString())
.content(
r.get("content").asString())
.createdAt(r.get("createdAt").asLocalDateTime(null))
.updatedAt(r.get("updatedAt").asLocalDateTime(null))
.build()
)
.all();
}
public Mono<Post> findOne(String id) {
return client
.query(
"MATCH (p:Post)" +
" WHERE p.id = $id" +
" RETURN p.id as id, p.title as title, p.content as content, p.createdAt as createdAt, p.updatedAt as updatedAt"
)
.bind(id).to("id")
.fetchAs(Post.class).mappedBy((ts, r) ->
Post.builder()
.id(r.get("id").asString())
.title(
r.get("title").asString())
.content(
r.get("content").asString())
.createdAt(r.get("createdAt").asLocalDateTime(null))
.updatedAt(r.get("updatedAt").asLocalDateTime(null))
.build()
)
.one();
}
public Mono<Post> save(Post post) {
var query = "MERGE (p:Post {id: $id}) \n" +
" ON CREATE SET p.createdAt=localdatetime(), p.title=$title, p.content=$content\n" +
" ON MATCH SET p.updatedAt=localdatetime(), p.title=$title, p.content=$content\n" +
" RETURN p.id as id, p.title as title, p.content as content, p.createdAt as createdAt, p.updatedAt as updatedAt";
return client.query(query)
.bind(post).with(data ->
Map.of(
"id", (data.getId() != null ? data.getId() : UUID.randomUUID().toString()),
"title", data.getTitle(),
"content", data.getContent()
)
)
.fetchAs(Post.class).mappedBy((ts, r) ->
Post.builder()
.id(r.get("id").asString())
.title(
r.get("title").asString())
.content(
r.get("content").asString())
.createdAt(r.get("createdAt").asLocalDateTime(null))
.updatedAt(r.get("updatedAt").asLocalDateTime(null))
.build()
)
.one();
}
public Mono<Integer> deleteAll() {
return client.query("MATCH (m:Post) DETACH DELETE m")
.run()
.map(it -> it.counters().nodesDeleted());
}
public Mono<Integer> deleteById(String id) {
return client
.query(
"MATCH (p:Post) WHERE p.id = $id" +
" DETACH DELETE p"
)
.bind(id).to("id")
.run()
.map(it -> it.counters().nodesDeleted());
}
}
For the complete codes, check spring-reactive-sample/boot-neo4j-rx-cypher.