Spring Data Neo4j: Failed to instantiate [org.neo4j.ogm.session.SessionFactory] - spring-data-neo4j

Question

I'm trying to add a Neo4j connection to my spring boot web application. I'm using this example at a template, but can't seem to get things working.
I keep getting a runtime error about not being able to create a SessionFactory: "Failed to instantiate [org.neo4j.ogm.session.SessionFactory]: Factory method 'sessionFactory' threw exception; nested exception is java.lang.NullPointerException"
I'm using spring boot version 1.5.1.RELEASE and here's the dependencies from my pom.xml file:
<dependencyManagement>
<dependencies>
<dependency>
<!-- Import dependency management from Spring Boot -->
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
<version>1.5.1.RELEASE</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<!-- For REST HTTP service and injection interfaces-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
<!-- For websocket service support -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-websocket</artifactId>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-messaging</artifactId>
</dependency>
<!-- For security features (user authentication, SSL) -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-security</artifactId>
</dependency>
<!-- For Neo4j integration -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-neo4j</artifactId>
</dependency>
</dependencies>
Here's my Spring Application Class:
#SpringBootApplication
#EnableTransactionManagement
#EnableNeo4jRepositories(basePackages="mycompany.ocelot.entities")
public class ServiceApp {
public static void main(String[] args) {
SpringApplication.run(ServiceApp.class, args);
}
}
Here's my entity class:
package mycompany.ocelot.entities;
import java.util.HashSet;
import java.util.Set;
import org.neo4j.ogm.annotation.GraphId;
import org.neo4j.ogm.annotation.NodeEntity;
import org.neo4j.ogm.annotation.Relationship;
#NodeEntity
public class User {
#GraphId private Long id;
private String username;
#SuppressWarnings("unused")
private User(){
// required by Neo4j
}
public User(String username){
this.username = username;
}
// getters & setters
public Long getId() {
return id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String toString(){
return username;
}
}
Here's my UserRepository class:
package mycompany.ocelot.entities;
import java.util.List;
import org.springframework.data.neo4j.repository.GraphRepository;
import org.springframework.data.repository.CrudRepository;
public interface UserRepository extends GraphRepository<User> {
User findByUsername(String username);
}
Here's the runtime error:
2017-02-23 19:55:04.928 WARN 4387 --- [ main] ationConfigEmbeddedWebApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'neo4jAuthenticationProvider': Unsatisfied dependency expressed through field 'user_repository'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userRepository': Unsatisfied dependency expressed through method 'setSession' parameter 0; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.data.neo4j.transaction.SharedSessionCreator#0': Cannot resolve reference to bean 'sessionFactory' while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory' defined in class path resource [org/springframework/boot/autoconfigure/data/neo4j/Neo4jDataAutoConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.neo4j.ogm.session.SessionFactory]: Factory method 'sessionFactory' threw exception; nested exception is java.lang.NullPointerException
2017-02-23 19:55:04.932 WARN 4387 --- [ main] o.s.boot.SpringApplication : Error handling failed (Error creating bean with name 'delegatingApplicationListener' defined in class path resource [org/springframework/security/config/annotation/web/configuration/WebSecurityConfiguration.class]: Initialization of bean failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.transaction.annotation.ProxyTransactionManagementConfiguration': Initialization of bean failed; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'org.springframework.context.annotation.ConfigurationClassPostProcessor.importRegistry' available)
I tried adding a Neo4j configuration class, but I just get a similar error.
package mycompany.ocelot.entities;
import org.neo4j.ogm.session.SessionFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.neo4j.repository.config.EnableNeo4jRepositories;
import org.springframework.data.neo4j.transaction.Neo4jTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;
#Configuration
#EnableNeo4jRepositories(basePackages = "mycompany.ocelot.entities")
#EnableTransactionManagement
public class Neo4jConfiguration {
#Bean
public Neo4jTransactionManager transactionManager() {
return new Neo4jTransactionManager(sessionFactory());
}
#Bean
public SessionFactory sessionFactory() {
// with domain entity base package(s)
return new SessionFactory("mycompany.ocelot.entities");
}
}
Update 1:
In trying to debug this, I tried removing things to determine when the problem starts happening. And I discovered that just including the dependency to the pom file causes the same exception. So I'm guessing there's some conflict between the spring modules I'm including.
Update 2:
I removed a dependency to another internal java project (which I didn't include in the pom file posted above) and that removed the runtime error. I did have to comment out quite a bit of code in this project as a result. So, the problem isn't between the spring modules, but somewhere between our code and spring-data-neo4j. Does anyone have any pointers on how to track down these kind of errors? The logging and stack trace don't seem much help as they don't reference our code. My knowledge spring's IoC (which I think is where the problem is) isn't that deep so any pointers on where to start would be helpful.

Answer 1

I ran the application from https://spring.io/guides/gs/accessing-data-neo4j without any issue with using the HTTP driver. I then added your other dependencies and had no issue either.
Try using upgrading to Boot 1.5.2 and do the following:
Remove the annotations: #EnableTransactionManagement and #EnableNeo4jRepositories(basePackages="mycompany.ocelot.entities"). These should already be configured by Spring Boot.
Add #EntityScan("<package containing your model code>") below #SpringBootApplication
Delete Neo4jConfiguration.
Make sure your configuration has the right username and password for your Neo4j database.

Answer 2

I faced a similar issue when I upgraded my application to Spring Boot version 1.5.2 - several null pointers at various places during Neo4j auto-configuration.
The issue to me was, that with the release of SDN 4.2 (which is referenced by the new Spring Boot version), the Neo4j's embedded driver does no longer include the neo4j kernel (see here). After I added the following two dependencies my application was up and running again.
<dependency>
<groupId>org.neo4j</groupId>
<artifactId>neo4j-ogm-embedded-driver</artifactId>
<version>2.1.1</version>
</dependency>
<dependency>
<groupId>org.neo4j</groupId>
<artifactId>neo4j</artifactId>
<version>3.1.1</version>
</dependency>
Maybe this can solve your problem as well.

Answer 3

I've just seen the same error in code I'm writing this morning: SessionFactory: "Failed to instantiate [org.neo4j.ogm.session.SessionFactory]: Factory method 'sessionFactory' threw exception; nested exception is java.lang.NullPointerException"
The problem occurred reliably and repeatable each time I started the application (which is a Spring Boot application implementing CommandLineRunner and connection to a Neo4j graph database).
I removed .java files one at a time (as D Perkins suggested in 'Update 2' above) until I tracked it down to a very simple piece of code, effectively:
package com.xxx.xxxx;
import java.nio.file.Path;
import lombok.Data;
#Data
public class MyClass {
private Path file;
private String content;
}
I've managed to avoid the problem by changing that class to use java.io.File rather than java.nio.file.Path. i.e. private File file;
Things I tried which didn't work included:
Replacing #Data with #Getter and #Setter.
Removing Lombok from the file and using source generation to create the getters and setters.
Removing the only code which called new MyClass().
I am using Lombok elsewhere in the project without issues. The project is a Spring Boot project.
I hope this information will prove useful.