NullPointerException on CrudRepository

Question

I have created a repository but when I call my repository it gives a NullPointerException everytime. Can someone help me figure out why?

My repository

@Repository
public interface WorkflowObjectRepository extends CrudRepository<WorkflowObject, String> {

    @Override
    WorkflowObject findOne(String id);

    @Override
    void delete(WorkflowObject workflowObject);

    @Override
    void delete(String id);

    @Override
    WorkflowObject save(WorkflowObject workflowObject);

}

My Object

@Data
@Entity
@Table(name = "workflowobject")
public class WorkflowObject {

    @GeneratedValue
    @Column(name="id")
    private String id;

    @Column(name = "state_name")
    private String stateName;

}

My test

public class Test {

    @Autowired
    static WorkflowObjectRepository subject;

    public static void main(String[] args) {

        final WorkflowObject obj = new WorkflowObject();
        obj.setId("maha");
        obj.setStateName("test");
        subject.findOne("maha");
    }

}

application.properties

spring.datasource.url=jdbc:postgresql://localhost:5432/vtr?
autoReconnect=true
spring.datasource.username=vtr
spring.datasource.password=vtr

Possible duplicate of [What is a NullPointerException, and how do I fix it?](http://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — Pradeep Simha, May 17 '17 at 08:45

score 3 · Answer 1 · answered May 17 '17 at 08:54

3

The problem is you are trying to autowire a static data member

@Autowired
static WorkflowObjectRepository subject;

What happens in your case is static is getting initialized before the bean so you are autowiring on null, just remove the static and deal with it as instance variable.

repositories are singletones so no point of making them static

answered May 17 '17 at 08:54

Amer Qarabsa

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when I remove the static, eclipse gives me an `error Cannot make a static reference to the non-static field subject ` for subject.findOne("test"); – Maha BENJEBARA May 17 '17 at 09:00
yeah you need to deal with your service now as an instance variable not static – Amer Qarabsa May 17 '17 at 09:04

score 0 · Accepted Answer · answered Jul 13 '20 at 14:14

In order to work properly with @Autowired you need to keep in mind that spring scans annotations to allow automatically classes load.

If you need to @Autowired some class, the class Test needs to have some annotation, that tells to Spring Boot to find it.

Your Test class need to have @Component, @Service, @Controller, @Repository, etc. Otherwise @Autowired will not work because Spring Boot not know your class and will not process it.

You can find some explanation here

NullPointerException on CrudRepository

2 Answers2