Spring MongoRepository 为空

Question

我有以下代码尝试使用 Spring Mongo Repository 将 POJO 对象（Actor）保存到 MongoDB 中，但存储库对象始终为 Null。我关注了多个示例，但主要是this one

POJO 类：

@Document(collection = "actors")
public class Actor 
{
  @Id
  private String id;
  ...
  //constructor
  //setters & getters
}

存储库：

public interface ActorRepository extends MongoRepository<Actor, String> 
{
  public Actor findByFNameAndLName(String fName, String lName);
  public Actor findByFName (String fName);
  public Actor findByLName(String lName);
}

使用存储库的服务：

@Service
public class ActorService 
{
  @Autowired
  private ActorRepository actorRepository;

  public Actor insert(Actor a)
  {
    a.setId(null);
    return actorRepository.save(a);
  }
} 

我从 REST 控制器类访问服务：

@RestController
public class Controllers 
{

  private static final Logger logger = Logger.getLogger(Controllers.class);
  private static final ApplicationContext ctx = new  AnnotationConfigApplicationContext(SpringMongoConfig.class);

  private ActorService actorService = new ActorService();

  @RequestMapping(value="/createActor", method=RequestMethod.POST)
  public @ResponseBody String createActor(@RequestParam(value = "fName") String fName,
        @RequestParam(value = "lName") String lName,
        @RequestParam(value = "role") String role)
  {
    return actorService.insert(new Actor(null,fName,lName,role)).toString();

  }

 ...
}

我从这一行得到的错误是 NullPointerException：return actorRepository.save(a); in the ActorService.insert() 方法。

知道为什么会这样吗？

编辑：这是 Spring 配置

@Configuration
public class SpringMongoConfig extends AbstractMongoConfiguration
{ 
    @Bean
    public GridFsTemplate gridFsTemplate() throws Exception 
    {
        return new GridFsTemplate(mongoDbFactory(), mappingMongoConverter());
    }

    @Override
    protected String getDatabaseName() 
    {
        return "SEaaS";
    }

    @Override
    @Bean
    public Mongo mongo() throws Exception 
    {
        return new MongoClient("localhost" , 27017 );
    }

    public @Bean MongoTemplate mongoTemplate() throws Exception 
    {
        return new MongoTemplate(mongo(), getDatabaseName());
    }    
}

Answer 1

问题是您没有使用 Spring 来获取 ActorService 依赖项 - 而是使用

手动实例化了依赖项

private ActorService actorService = new ActorService();.

以下代码是将ActorService 依赖项注入控制器的最简单修复方法。

@RestController
public class Controllers 
{

  private static final Logger logger = Logger.getLogger(Controllers.class);
  private static final ApplicationContext ctx = new  AnnotationConfigApplicationContext(SpringMongoConfig.class);

  @Autowired 
  private ActorService actorService;

  @RequestMapping(value="/createActor", method=RequestMethod.POST)
  public @ResponseBody String createActor(@RequestParam(value = "fName") String fName,
        @RequestParam(value = "lName") String lName,
        @RequestParam(value = "role") String role)
  {
    return actorService.insert(new Actor(null,fName,lName,role)).toString();

  }

 ...
}