CrudRepository findById 返回 null mysql

Question

I have a Databaseintem, and I have as Id a string. I created an ItemRepository and declared findById, the entry is in the database, but I get null on findById.

import org.springframework.data.repository.CrudRepository; import org.springframework.transaction.annotation.Transactional;

Repository:

@Transactional 
public interface ItemRepository extends CrudRepository<Item, String> {
    public Item findById(String id);
}

Item:

@Entity
public class Item{
    private String id;
    private String idTrans;
    private String name;
    private Date created;
    private Date modified;

@Id
public String getId() {
    return id;
}
----

I have an ItemService that interacts with the repository and from ItemController I implement a rest api, get.

ItemController:

   @Controller
   @RequestMapping(value = "/item")
   public class ItemController {

   @RequestMapping( value = "/{id}", method = RequestMethod.GET )
   @ResponseStatus( HttpStatus.OK )
   @ResponseBody
   public String getItem( @PathVariable( "id" ) String id){
      Preconditions.checkNotNull( id );
      logger.info("1. getAAA " + id); // prints
      Item a = itemService.getItem( id );
      logger.info("2. getAAA " + a);
      return "a : ";// + a.getName();
   }

entry in DB"

| token1495528421393 | 2017-05-23 11:33:41 | Itemnull |               0 |        |          0 |          0 | 2017-05-23 11:33:41 |Item1

Request GET:

curl -H "Content-Type: application/json" -X GET http://localhost:8090/item/token1495528421393

• item is null on findById

Answer 1

I have just run exactly in the same issue some days ago, then i have found out that the reason why this was happening was that the entity which i was retrieving had a foreign reference to another entity which thereafter had as well another foreign reference to a third entity and the latter of these [references] was configured as not null , but the problem was that when checking in the database the looked item had effectively a null value in the foreign key; so when the persistence framework was translating the service into a query, it was making an inner join rather than an outer join which removed the entity from the results since the join between the second and third entity was failing due to the null values. Removing the not null clause in the second entity helped in fixing the issue.

Please check if your entities are not mapped in similar way.