[英]Implementing findOne in Spring Data (MongoDB)
我在执行MongoOperations类的findOne方法时遇到一些问题,目前此方法返回null。 我在mongoDB中的数据结构如下所示:
> db.news.find({_id:1})
{ "_id" : 1, "title" : "first title", "text" : "first text" }
> db.news.find({_id:{$type:1}})
{ "_id" : 1, "title" : "first title", "text" : "first text" }
如您所见,_id字段具有Double类型。 我的Java类看起来像这样:
@Repository
public class NewsService {
@Autowired
private MongoOperations mongoOperations;
public static final String COLLECTION_NAME = "news";
//this method executes ok
public List<NewsEntity> getAllNews() {
return mongoOperations.findAll(NewsEntity.class, COLLECTION_NAME);
}
//but this method return null
public NewsEntity getNewsDetail(Long id) {
return mongoOperations.findOne(Query.query(Criteria.where("_id").is(id)), NewsEntity.class);
}
实体类:
@Document
public class NewsEntity {
@Id
private Long id;
private String title;
private String text;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getText() {
return text;
}
public void setText(String text) {
this.text = text;
}
}
和Spring控制器:
@Controller
public class MainController {
@Autowired
private NewsService newsService;
@RequestMapping(value="/news/details/{newsId}",method = RequestMethod.GET)
public String getNewsDetails(ModelMap model, @PathVariable("newsId") Long newsId) {
//newsEnt is null here...
NewsEntity newsEnt = newsService.getNewsDetail(newsId);
model.addAttribute("newsDet", newsEnt);
return "newsdetails";
}
}
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