CRUD repository not working in a "simple" java class

Question

I have a spring-boot application with CRUD repository and a mysql database. When I use this repositories in a REST controller, I have no problems but I need to use one in a simple java class but it doesn't work.

I want to load all the residentStatEntities in a List to write in a CSV file but I can't load it.

Here are my code :

CRUD repository:

@Repository
public interface ResidentStatDBRepository extends CrudRepository<ResidentStatEntity, Long> {
    List<ResidentStatEntity> findAll();
}

Java class :

public class ResetDB {

    /**
     * CRUD Repository
     */
    @Autowired
    private  ResidentStatDBRepository residentStatDBRepository;



    /**
     * Delete DB and save his content in a CSV file
     * @throws Exception
     */
    public void save()throws Exception{
        //open file
        String csvFile = "residentStat.csv";
        FileWriter writer = new FileWriter(csvFile, true);
        //get list of all stat
        List<ResidentStatEntity> residentStatEntities = residentStatDBRepository.findAll();
}

Here are the message print in the console :

java.lang.NullPointerException
    at com.example.sems.ResetDB.save(ResetDB.java:36)
    at com.example.sems.SemsApplication$1.run(SemsApplication.java:52)
    at java.util.TimerThread.mainLoop(Timer.java:555)
    at java.util.TimerThread.run(Timer.java:505)

Here is where I use the ResetDB class

@SpringBootApplication
public class SemsApplication {

    public static void main(String[] args) {
        SpringApplication.run(SemsApplication.class, args);
        int MINUTES = 1; // The delay in minutes
        Timer timer = new Timer();
        timer.schedule(new TimerTask() {
            @Override
            public void run() { // Function runs every MINUTES minutes.
                try{
                    new ResetDB().save();
                    System.out.println("ok");
                }catch (Exception e){
                    e.printStackTrace();
                }
            }
        }, 0, 1000 * 60 * MINUTES);
        // 1000 milliseconds in a second * 60 per minute * the MINUTES variable.
    }
}

I call this function every minutes maybe the problem is because it's in the main method ?

Thanks in advance for you answer :)

@Stultuske ResetDB resetdb = new ResetDB(); and then I call the method like this : resetdb.save(); — Flo_H99, Mar 12 '19 at 12:31
@Flo_H99 Spring's component scan is probably not picking up the repository. Check [ComponentScan](https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/context/annotation/ComponentScan.html) and [EnableJpaRepositories("path.to.your.repo")](https://docs.spring.io/spring-data/jpa/docs/current/api/org/springframework/data/jpa/repository/config/EnableJpaRepositories.html) annotations. — Januson, Mar 12 '19 at 12:35

score 0 · Answer 1 · answered Mar 12 '19 at 12:29

0

ResetDB is not a spring managed bean.

Annotate ResetDB with @Component it should solve the problem.

answered Mar 12 '19 at 12:29

Santosh b

729
1
8
19

doubtful. if it's not a spring managed bean, chances are small that it's autowired, so it'll likely take more than just adding that annotation – Stultuske Mar 12 '19 at 12:30
It still doesn't work – Flo_H99 Mar 12 '19 at 12:33
@Flo_H99 that is because that is only a part of the answer. – Stultuske Mar 12 '19 at 12:33
@Flo_H99 Are you getting the same error? – Santosh b Mar 12 '19 at 13:13
@Santoshb yes and I also tried the soluce of Stultuske, I will edit my question to show also when I call the method save – Flo_H99 Mar 12 '19 at 13:15
Add private @Autowired ResetDB resetDB Replace new ResetDB() with resetDB – Santosh b Mar 12 '19 at 13:41

score 0 · Answer 2 · answered Mar 12 '19 at 12:33

0

In order for ResetDB to be able to manage your Bean using Spring injection, ResetDB itself must be instantiated by that system.

Add the @Component annotation to your ResetDB class, and have your instance of ResetDB autowired as well.

answered Mar 12 '19 at 12:33

Stultuske

9,296
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37

CRUD repository not working in a "simple" java class

2 Answers2