LastModifiedBy

Question

如何延迟加载带有@LastModifiedBy注释的多对一列？

例如，我有createdBy和lastModifiedBy列：

@ManyToOne(fetch = FetchType.LAZY, optional = false)
@JoinColumn(name = "manager_id")
@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "id")
@JsonIdentityReference(alwaysAsId = true)
private User manager;

@ManyToOne(fetch = FetchType.LAZY, optional = false)
@CreatedBy
@JoinColumn(name = "created_by")
@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "id")
@JsonIdentityReference(alwaysAsId = true)
@JsonProperty("created_user_id")
private User createdBy;

@ManyToOne(fetch = FetchType.EAGER, optional = false)
@LastModifiedBy
@JoinColumn(name = "last_modified_by")
@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "id")
@JsonIdentityReference(alwaysAsId = true)
@JsonProperty("last_modified_user_id")
private User lastModifiedBy;

这是工作。但是，当我尝试延迟加载列lastModifiedBy (fetch = FetchType.LAZY，可选= false)时，我就出错了：

2016-06-18 23:10:36,399 WARN  [org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver] (default task-8) Failed to write HTTP message: org.springframework.http.converter.HttpMessageNotWritableException: Could not write content: Problem accessing property 'id': null (through reference chain: com.smcontact.cms.model.project.Project["manager"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Problem accessing property 'id': null (through reference chain: com.smcontact.cms.model.project.Project["manager"])

如何修复此错误？

Answer 1

解决方案:注册hibernate模块。

Hibernate5Module hibernateModule = new Hibernate5Module();
objectMapper.registerModule(hibernateModule);