[英]Jackson JSON and lazy loaded collections
我有一类懒加载一个集合。 现在,我有两个不同的查询,一个查询在不收集数据的情况下加载数据,另一个在查询整个数据。 当执行不加载集合的查询时,出现以下错误:
JsonMappingException: failed to lazily initialize a collection of role: Player.goals
我试图通过使用@JsonInclude(JsonInclude.Include.NON_EMPTY)
批注来修复此问题,但这没有帮助。
如何基于同一个类产生两个不同的JSON结果?
更新:更新了结构并添加了JSONView,但错误没有改变。
模型
@Entity
public class User implements Serializable {
@OneToMany(cascade = CascadeType.ALL, mappedBy = "owner")
private Collection<Team> teams = new ArrayList<Team>();
}
@Entity
public class Team implements Serializable {
...
@OneToMany(cascade = CascadeType.ALL, mappedBy = "team", targetEntity = Player.class, fetch = FetchType.EAGER)
@JsonView(UserViews.User.class)
private Collection<Player> players = new ArrayList<Player>();
...
}
@Entity
public class Player implements Serializable {
@OneToMany(cascade = CascadeType.ALL, mappedBy = "player", targetEntity = Goal.class, fetch = FetchType.LAZY)
@JsonView(UserViews.UserWithGoals.class)
private Collection<Goal> goals= new ArrayList<Goal>();
...
}
查询
@Query("SELECT u FROM User u WHERE u.id = :id")
Team findById(@Param("id") Long id);
弹簧控制器
@RequestMapping(headers = "Accept=application/json")
@JsonView(UserViews.User.class)
public @ResponseBody Team getTeam(Authentication authentication) {
User user = userService.findById(1);
return team;
}
通过这种配置访问,控制器不应加载Player类的Goals
,但这正是JSONMappingException中提到的部分。 知道有什么问题吗?
也许您可以看看Jackson JsonViews: http ://wiki.fasterxml.com/JacksonJsonViews。
您将必须在实体中定义两个不同的视图:
@Entity
public class Team implements Serializable {
...
@OneToMany(cascade = CascadeType.ALL, mappedBy = "team", targetEntity = Player.class, fetch = FetchType.LAZY)
@JsonView(FullView.class)
private Collection<Player> players = new ArrayList<Player>();
...
}
并在调用方方法中激活视图(通常是JAX-RS实现-请参见http://wiki.fasterxml.com/JacksonJsonViews#Views_with_JAX-RS )
这样做,播放器列表在第一种情况下将被忽略,并且仅在列表被填充时才以JSON序列化。
语法不正确,对不起,但您明白了
为了防止延迟,您可以在Spring中配置xml或java中的OpenEntityManagerInVew过滤器(不记得确切的语法):
<filter>
<filter-name>openEntityManagerInViewFilter</filter-name>
<filter-class>org.springframework.orm.jpa.support.OpenEntityManagerInViewFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>openEntityManagerInViewFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
希望能帮助到你
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