Spring Data JPA Repository findAll() Null Pointer

Question

I have a Spring-Boot API with the endpoint below. It is throwing a Null Pointer Exception on a Spring Data JPA findAll query; when I comment out this line, I get no errors. It seems that I am getting a null result from the repository query, but I know the data is there from querying the DB directly. I cannot understand why I'm getting a null for topicsLookup variable... Can anyone point me in the right direction?

Resource:

@RequestMapping(value = "/lectures/{lectureId}",
        method = RequestMethod.GET,
        produces = MediaType.APPLICATION_JSON_VALUE)
public Map<String, SpeakerTopicLectures> getLecture(@PathVariable Long lectureId){

        Long requestReceived = new Date().getTime();
        Map<String, SpeakerTopicLectures> result = new HashMap<>();

        log.debug("** GET Request to getLecture");
        log.debug("Querying results");

        List<SpeakerTopicLectures> dataRows = speakerTopicLecturesRepository.findBySpeakerTopicLecturesPk_LectureId(lectureId);

        // This line throws the error
        List<SpeakerTopic> topicsLookup = speakerTopicsRepository.findAll();

        // Do stuff here...

        log.debug("Got {} rows", dataRows.size());
        log.debug("Request took {}ms **", (new Date().getTime() - requestReceived));

        // wrap lecture in map object
        result.put("content", dataRows.get(0));

        return result;
}

Java Bean:

@Entity
@Table(name = "speaker_topics")
@JsonInclude(JsonInclude.Include.NON_NULL)
@Data
public class SpeakerTopic implements Serializable {

    @Id
    @Column(name = "topic_id")
    private Long topicId;

    @Column(name = "topic_nm")
    private String topicName;

    @Column(name = "topic_desc")
    private String topicDesc;

    @Column(name = "topic_acm_relt_rsce")
    private String relatedResources;

}

Repository:

import org.acm.dl.api.domain.SpeakerTopic;
import org.springframework.data.jpa.repository.JpaRepository;

public interface SpeakerTopicsRepository extends JpaRepository<SpeakerTopic,Long> {

}

Answer 1

The most likely cause is that speakerTopicsRepository is itself null, which is probably caused by forgetting to autowire it, e.g.

public class YourController {

  @Autowired private SpeakerTopicsRepository speakerTopicsRepository;

  @RequestMapping(value = "/lectures/{lectureId}",method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
  public Map<String, SpeakerTopicLectures> getLecture(@PathVariable Long lectureId) {
     // your method...
  }

}

Answer 2

the repository is not autowired in your controller.