Spring REST， JSON “无法处理托管/反向引用 'defaultReference'” 415 不支持的媒体类型

我正在尝试使用Spring boot/Spring RestController后端从AngularJS前端 http://localhost:9095/translators。

我可以做一个GET，响应如下：

[{"userId":1,"firstName":"John","lastName":"Doe","emailId":"john.doe@inc.com","languages":[{"languageId":1,"languageCode":"gb","source":true}],"translations":[{"translationId":3,"sourceId":1,"sourceText":"Hello","targetId":null,"targetText":null,"translationStatus":"DUE"}],"userType":"TRANSLATOR"}

当我发布下面的json时，我得到错误响应

开机自检数据：

{
                    firstName: "zen",
                    lastName: "cv",
                    emailId: "email",
                    userType: "TRANSLATOR",
                    languages : [{languageId:1,languageCode:"gb",source:true}]
}

错误：

{
timestamp: 1422389312497
status: 415
error: "Unsupported Media Type"
exception: "org.springframework.web.HttpMediaTypeNotSupportedException"
message: "Content type 'application/json' not supported"
path: "/translators"
}

我已确保我的控制器具有正确的 Mediatype 注释。

@RestController
@RequestMapping("/translators")
public class TranslatorController {
    @Autowired
    private UserRepository repository;

    @RequestMapping(method = RequestMethod.GET)
    public List findUsers() {
        return repository.findAll();
    }

    @RequestMapping(value = "/{userId}", method = RequestMethod.GET)
    public User findUser(@PathVariable Long userId) {
        return repository.findOne(userId);
    }

    @RequestMapping(method = RequestMethod.POST, consumes = MediaType.APPLICATION_JSON_VALUE, produces = MediaType.APPLICATION_JSON_VALUE)
    public User addTranslator(@RequestBody User user) {
        //translation.setTranslationId(null);
        return repository.saveAndFlush(user);
    }

    @RequestMapping(value = "/{translatorId}", method = RequestMethod.PUT)
    public User updateTranslation(@RequestBody User updatedUser, @PathVariable Long userId) {
        //updatedTranslation.setTranslationId(translationId);
        return repository.saveAndFlush(updatedUser);
    }

    @RequestMapping(value = "/{translatorId}", method = RequestMethod.DELETE)
    public void deleteTranslation(@PathVariable Long translationId) {
        repository.delete(translationId);
    }
}

经过一些研究，也通过查看日志输出，我意识到这是一个误导性的错误消息，并且问题实际上发生在序列化/反序列化Json时

在日志文件中，我发现

2015-01-27 21：08：32.488 WARN 15152 --- [nio-9095-exec-1] .c.j.MappingJackson2HttpMessageConverter ： 无法评估类型 [简单类型，类 User]： java.lang.IllegalArgumentException： 无法处理托管/反向引用 'defaultReference'： back 引用类型 （java.util.List） 与托管类型 （User） 不兼容

这是我的类用户和类转换（为了简洁起见，省略了 getter、setter、构造函数等）

@Entity
@Table(name = "users")
public class User {

    @Id
    @GeneratedValue(strategy= GenerationType.AUTO)
    @Column(name = "user_id")
    private long userId;

    @Column(name = "first_name")
    private String firstName;

    @Column(name = "last_name")
    private String lastName;

    @Column(name = "email_id")
    private String emailId;

    @ManyToMany
    @JoinTable(name = "languages_users", joinColumns = { @JoinColumn(name = "user_id")},
            inverseJoinColumns = {@JoinColumn(name = "lang_id")})
    @JsonManagedReference
    private List<Language> languages = new ArrayList<Language>();

    @OneToMany(mappedBy = "translator", fetch = FetchType.EAGER)
    @JsonManagedReference
    private List<Translation> translations;

    @Enumerated(EnumType.STRING)
    private UserType userType;
}

@Entity
@Table(name = "translations")
public class Translation {

    @Id
    @GeneratedValue(strategy= GenerationType.IDENTITY)
    @Column(name = "translation_id")
    private Long translationId;

    @Column(name = "source_lang_id")
    private Long sourceId;

    @Column(name = "source_text")
    private String sourceText;

    @Column(name = "target_lang_id")
    private Long targetId;

    @Column(name = "target_text")
    private String targetText;

    @Enumerated(EnumType.STRING)
    @Column(name = "status")
    private TranslationStatus translationStatus;

    @ManyToOne
    @JoinColumn(name = "translator_id")
    @JsonBackReference
    private User translator;
}

我的问题是：如何为上述实体正确设置 JsonManagedReference 和 JsonBackReference？我确实阅读了文档，我无法根据错误消息找出这里出了什么问题。