Can't use the added function in Repository - spring

Question

I'm using Spring Data Neo4j 2.4.4 for my project. This is some in project:
User:
UserRepository:
I can still use the built-in functions in Repository such as save(), findAll(),... but when I add and use some functions, for example "existsByUsername", it has error:
11:53:26.562 [http-nio-8081-exec-1] WARN o.s.d.n.c.Neo4jPersistenceExceptionTranslator - Don't know how to translate exception of type class org.neo4j.driver.exceptions.NoSuchRecordException
Then, I try to add query for function, it is still
Could you help me to determine this error and give me a solution? Thank you!\
Updated:
I call API in Postman, I received this result while my DB has only 1 user:
{
"error": "Records with more than one value cannot be converted without a mapper.; nested exception is java.lang.IllegalArgumentException: Records with more than one value cannot be converted without a mapper."
}

Answer 1

As your exception states, no record is returned from Neo4j and thus it cannot be mapped to a Boolean.
Best would be to use Optional<User> and check with isPresent()
#Query("MATCH (n:User {username: $username}) RETURN n")
Optional<User> existsForUsername(String username);
That said, it is already handled by Spring Data without using a custom query :
boolean existsByUsername(String username);
Reference : https://docs.spring.io/spring-data/neo4j/docs/current/reference/html/#appendix.query.method.subject

Answer 2

There is a rather obscure set of references on github site for the NEO4J Spring Data: here
It seems that the existsBy property was omitted. It is being fixed, but whether that has made it to the Spring Data repository is another matter. You don;t say which version of the Spring-boot-starter-neo4j you are using, but you may care to use this one and see if it works;
<!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-data-neo4j -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-neo4j</artifactId>
<version>2.4.4</version>
</dependency>

Answer 3

In general, the other answers here are right. But, if you're using Spring Boot 2.4.4, OGM is no longer supported. It now uses a model called SDN (or at least it was when it was under development). You may just have a dependency issue. Here's part of my Gradle build file, these should be all the dependencies you need:
import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
plugins {
application
id("org.springframework.boot") version "2.4.4"
id("io.spring.dependency-management") version "1.0.10.RELEASE"
}
java.sourceCompatibility = JavaVersion.VERSION_11
configurations {
compileOnly {
extendsFrom(configurations.annotationProcessor.get())
}
}
repositories {
mavenCentral()
}
dependencies {
implementation("org.springframework.boot:spring-boot-starter-actuator")
implementation("org.springframework.boot:spring-boot-starter-data-neo4j")
implementation("org.springframework.boot:spring-boot-starter-security")
implementation("org.springframework.boot:spring-boot-starter-web")
}