java - Jackson 忽略层次结构嵌套类中的 @JsonIgnore 注释

Question

我目前正在开发一个基于 spring 的 java 应用程序 长话短说 - 这是我用来从数据库检索对象、对其进行一些计算并渲染它的代码

@RequestMapping(value = { "/mapping" }, method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
public Object getMasterAppMappingById(
        @PathVariable(value = "masterAppId") Integer masterAppId) {  

    RestBaseVO masterAppMappingRestBaseVO = new RestBaseVO();

    MasterAppMappingTreeDetailsVO masterAppMappingTreeDetailsById = applicationDeviceServices.getMasterAppMappingTreeDetails(masterAppId, true);

    return masterAppMappingTreeDetailsById;
}

我遇到的问题是，代码一直很好，直到 jackson 介入并转换它。 return 语句是我的瓶颈

方法 getMasterAppMappingTreeDetails 工作完美并且执行良好

由jackson渲染的json显示在pastebin上的以下url中 http://pastebin.com/erRDtweZ

如您所见 - 它相当大

被序列化的类如下

public class MasterAppMappingTreeDetailsVO {

@JsonProperty("id")
private Integer id;

@JsonProperty("mappingId")
private Integer mappingId;

@JsonProperty("parentMappingId")
private Integer parentMappingId;



 @JsonProperty("isQuestion")
    private boolean isQuestion;

    @JsonProperty("isAnswer")
    private boolean isAnswer;

    @JsonProperty("isApplication")
    private boolean isApplication;

    @JsonProperty("displayLabel")
    private String displayLabel;

    @JsonProperty("additionalText1")
    private String additionalText1;

    @JsonProperty("imageUrl")
    private String imageUrl;

    @JsonProperty("imageDateUpdated")
    private Long imageDateUpdated;

    @JsonProperty("appId")
    private Integer appId;

    @JsonProperty("appName")
    private String appName;

    @JsonProperty("children")
    private List<MasterAppMappingTreeDetailsVO> children;

    @JsonProperty("menuStyle")
    private MenuStyleVO menuStyle;

}


    @Entity
@Table(name = "menu_style")
@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})
public class MenuStyleVO extends BaseDAOVO implements Serializable{

    /**
     * 
     */
    private static final long serialVersionUID = 3697798179195096156L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id", unique = true, nullable = false)
    private Integer id;

    @Column(name = "menuStyleName", unique = false, nullable = false, length = 200)
    private String menuStyleName;

    @Column(name = "menuTemplate", unique = false, nullable = false, length = 200)
    private String menuTemplate;

    @OneToOne(fetch = FetchType.EAGER)
    @Cascade({ CascadeType.SAVE_UPDATE })
    @JoinColumn(name="logo_id")
    @JsonProperty("logo")
    private ApplicationImageVO logo;

    @Column(name = "logoAlignment", unique = false, nullable = true, length = 20)
    private String logoAlignment;

    @Column(name = "backArrowColor", unique = false, nullable = true, length = 7)
    private String backArrowColor;    

    @OneToOne(fetch = FetchType.EAGER)
    @Cascade({ CascadeType.SAVE_UPDATE })
    @JoinColumn(name="backArrowIcon_id")
    @JsonProperty("backArrowIcon")
    private ApplicationImageVO backArrowIcon;

    @Column(name = "questionLabelTextColor", unique = false, nullable = true, length = 7)
    private String questionLabelTextColor;  

    @Column(name = "headerBackgroundColor", unique = false, nullable = true, length = 7)
    private String headerBackgroundColor;      

    @Column(name = "headerBackgroundOpacity", unique = false, nullable = true)
    private Integer headerBackgroundOpacity; 

    @Column(name = "mainBackgroundColor", unique = false, nullable = true, length = 7)
    private String mainBackgroundColor;      

    @Column(name = "mainBackgroundOpacity", unique = false, nullable = true)
    private Integer mainBackgroundOpacity; 

    @OneToOne(fetch = FetchType.EAGER)
    @Cascade({ CascadeType.SAVE_UPDATE })
    @JoinColumn(name="backgroundImageLandscape_id")
    @JsonProperty("backgroundImageLandscape")
    private ApplicationImageVO backgroundImageLandscape;

    @OneToOne(fetch = FetchType.EAGER)
    @Cascade({ CascadeType.SAVE_UPDATE })
    @JoinColumn(name="backgroundImagePortrait_id")
    @JsonProperty("backgroundImagePortrait")
    private ApplicationImageVO backgroundImagePortrait;

    @Column(name = "containerColor", unique = false, nullable = true, length = 7)
    private String containerColor;      

    @Column(name = "containerOpacity", unique = false, nullable = true)
    private Integer containerOpacity; 

    @Column(name = "containerLineDividerColor", unique = false, nullable = true, length = 7)
    private String containerLineDividerColor;      

    @Column(name = "containerLineDividerOpacity", unique = false, nullable = true)
    private Integer containerLineDividerOpacity; 

    @Column(name = "optionIconSize", unique = false, nullable = true)
    private Integer optionIconSize; 

    @Column(name = "optionLabelTextColor", unique = false, nullable = true, length = 7)
    private String optionLabelTextColor;     

    @Column(name = "optionTaglinePosition", unique = false, nullable = true, length = 20)
    private String optionTaglinePosition;   

    @Column(name = "optionTaglineTextColor", unique = false, nullable = true, length = 7)
    private String optionTaglineTextColor; 

    @Column(name = "optionSelectionArrowColor", unique = false, nullable = true, length = 7)
    private String optionSelectionArrowColor;

    @OneToOne(fetch = FetchType.EAGER)
    @Cascade({ CascadeType.SAVE_UPDATE })
    @JoinColumn(name="optionSelectionArrowIcon_id")
    @JsonProperty("optionSelectionArrowIcon")
    private ApplicationImageVO optionSelectionArrowIcon;

}

任何人都可以就如何提高此 json 调用的性能或如何提高我的应用程序的 Jackson 性能提供任何建议吗？

Answer 1

jackson 的问题
如果您使用 Jackson API 序列化实体类，那么放置 @JsonIgnore 注释可能足以满足一种情况，但不能满足所有情况。
如果您有一些延迟加载的属性，那么一旦 Jackson 序列化对象，这些属性就会被加载，否则您必须急切地加载它们，这肯定会对性能产生不利影响。
如果你的类之间有关系(一对多；多对多等)，那么 jackson 在序列化对象时也会加载所有依赖实体，你也可能会遇到循环依赖问题，即父加载子和子加载父。< br/> 当然，有一种方法可以使用 Jackson API 来克服这个问题，但从长远来看，它会成为一个瓶颈。

解决方案
根据我的说法，最好的方法是为您想要返回的内容创建模型类，并在从 Controller 返回之前加载并返回该类。

这有一些优点和缺点。

缺点:
1. 当然会有额外的类和额外的代码需要维护。

优点:
1. 模型类将是独立的，并且不会对实体类有任何依赖。
2.任何一个类的任何改变都不会影响其他类。
3. 不需要渲染的属性可以避免。
4. 您可以轻松修改实体类，并且在模型类发生更改之前， View 中不会发生更改。

希望这有帮助!!