Spring Boot get 请求不使用@OneToMany 获取第三级对象

Question

我的数据库表设计如下。

使用这种结构，使用 Springboot，我无法获取 TABLE-1 的所有子元素直到 TABLE-3

下面是实体class相同

TABLE-1 (SDKMainCollection.java)

@Entity
@Table(name="sdkmaincollection")
public class SDKMainCollection {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;
    private String sdkgroupname;
    @JsonIgnore
    @OneToMany(mappedBy = "sdkcollectionobj", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    private Set<SDKCollection> sdkcollection;

    public SDKMainCollection() {
    }

    public SDKMainCollection(int id,String sdkGroupName) {
        this.id= id;
        this.sdkgroupname =sdkGroupName;
    }

    public SDKMainCollection(String sdkGroupName) {
        this.sdkgroupname =sdkGroupName;
    }
    //Getters and Setters
}

TABLE-2 (SDKCollection.java)

@Entity
@Table(name="sdkcollection")
public class SDKCollection {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;
    private String sdktitle;
    private String sdkid;
    private String sdkresourceid;
    private String sdkdescription;
    private String sdkimageName;
    @JsonIgnore
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "sdkmaincollection_id")
    private SDKMainCollection sdkcollectionobj;
    @JsonIgnore
    @OneToMany(mappedBy = "sdkcolsubobj", cascade = CascadeType.ALL, fetch=FetchType.LAZY) 
    private Set<Ads> ads;

    public SDKCollection() {
    }
    public SDKCollection(int id, String sdkTitle, String sdkId, String sdkresourceId, String sdkdescription,
            String sdkimageName,SDKMainCollection sdkObj) {
        this.id = id;
        this.sdktitle = sdkTitle;
        this.sdkid = sdkId;
        this.sdkresourceid = sdkresourceId;
        this.sdkdescription = sdkdescription;
        this.sdkimageName = sdkimageName;
        this.sdkcollectionobj = sdkObj;
    }
    public SDKCollection(String sdkTitle, String sdkId, String sdkresourceId, String sdkdescription,
            String sdkimageName,SDKMainCollection sdkObj) {

        this.sdktitle = sdkTitle;
        this.sdkid = sdkId;
        this.sdkresourceid = sdkresourceId;
        this.sdkdescription = sdkdescription;
        this.sdkimageName = sdkimageName;
        this.sdkcollectionobj = sdkObj;
    }
    //Getters and Setters
}

TABLE-3 (Ads.java)

@Entity
@Table(name="ads")
public class Ads {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;
    private String adtitle;
    private String adtag;
    private String adtype;
    private String imagename;
    private String controlid;
    @JsonIgnore
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "sdkcollection_id")
    private SDKCollection sdkcolsubobj;

    public Ads() {

    }
    public Ads(int id, String adTitle, String adTag, String adType, String imageName, String controlID,
            SDKCollection sdkcollection     
            ) {
        this.id = id;
        this.adtitle = adTitle;
        this.adtag = adTag;
        this.adtype = adType;
        this.imagename = imageName;
        this.controlid = controlID;
        this.sdkcolsubobj = sdkcollection;
    }
    public Ads(String adTitle, String adTag, String adType, String imageName, String controlID
            ,SDKCollection sdkcollection) {
        this.adtitle = adTitle;
        this.adtag = adTag;
        this.adtype = adType;
        this.imagename = imageName;
        this.controlid = controlID;
        this.sdkcolsubobj = sdkcollection;
    }
    //Getters and Setters
}

下面是我的控制器class，用于获取元素

@RestController
@RequestMapping("/api/sdk/")
@CrossOrigin
public class GetSDKController {
    @Autowired
    private SDKMainCollectionRepo sdkMainCollectionRepo;
    @Autowired
    private SDKCollectionRepo sdkCollectionRepo;
    @Autowired
    private AdsRepo adsRepo;
    @GetMapping("/getAllSDKs")
    public List<SDKMainCollection> getAllSDK(){
        sdkDataMapper = new SDKDataMapper(sdkMainCollectionRepo,sdkCollectionRepo,adsRepo);
        List<SDKMainCollection> totalResp  = (List<SDKMainCollection>) sdkMainCollectionRepo.findAll();
        System.out.println("getAllSDK = totalResp "+totalResp);

        //NOT GETTING WHAT IS EXPECTED

        return totalResp;
    }
}

低于我的预期，但我得到 Whosebug error

Whosebug 错误日志：

java.lang.WhosebugError: null
    at java.util.AbstractCollection.toString(Unknown Source) ~[na:1.8.0_131]
    at org.hibernate.collection.internal.PersistentSet.toString(PersistentSet.java:328) ~[hibernate-core-5.3.7.Final.jar:5.3.7.Final]
    at java.lang.String.valueOf(Unknown Source) ~[na:1.8.0_131]
    at java.lang.StringBuilder.append(Unknown Source) ~[na:1.8.0_131]
    at com.dvservices.models.SDKMainCollection.toString(SDKMainCollection.java:59) ~[classes/:na]
    at java.lang.String.valueOf(Unknown Source) ~[na:1.8.0_131]
    at java.lang.StringBuilder.append(Unknown Source) ~[na:1.8.0_131]
    at com.dvservices.models.SDKCollection.toString(SDKCollection.java:118) ~[classes/:na]
    at java.lang.String.valueOf(Unknown Source) ~[na:1.8.0_131]
    at java.lang.StringBuilder.append(Unknown Source) ~[na:1.8.0_131]
    at java.util.AbstractCollection.toString(Unknown Source) ~[na:1.8.0_131]
    at org.hibernate.collection.internal.PersistentSet.toString(PersistentSet.java:328) ~[hibernate-core-5.3.7.Final.jar:5.3.7.Final]
    at java.lang.String.valueOf(Unknown Source) ~[na:1.8.0_131]
    at java.lang.StringBuilder.append(Unknown Source) ~[na:1.8.0_131]
    at com.dvservices.models.SDKMainCollection.toString(SDKMainCollection.java:59) ~[classes/:na]
    at java.lang.String.valueOf(Unknown Source) ~[na:1.8.0_131]
    at java.lang.StringBuilder.append(Unknown Source) ~[na:1.8.0_131]
    at com.dvservices.models.SDKCollection.toString(SDKCollection.java:118) ~[classes/:na]
    at java.lang.String.valueOf(Unknown Source) ~[na:1.8.0_131]
    at java.lang.StringBuilder.append(Unknown Source) ~[na:1.8.0_131]
    at java.util.AbstractCollection.toString(Unknown Source) ~[na:1.8.0_131]
    at org.hibernate.collection.internal.PersistentSet.toString(PersistentSet.java:328) ~[hibernate-core-5.3.7.Final.jar:5.3.7.Final]
    at java.lang.String.valueOf(Unknown Source) ~[na:1.8.0_131]
    at java.lang.StringBuilder.append(Unknown Source) ~[na:1.8.0_131]
    at com.dvservices.models.SDKMainCollection.toString(SDKMainCollection.java:59) ~[classes/:na]
    at java.lang.String.valueOf(Unknown Source) ~[na:1.8.0_131]
    at java.lang.StringBuilder.append(Unknown Source) ~[na:1.8.0_131]
    at com.dvservices.models.SDKCollection.toString(SDKCollection.java:118) ~[classes/:na]
    at java.lang.String.valueOf(Unknown Source) ~[na:1.8.0_131]
    at java.lang.StringBuilder.append(Unknown Source) ~[na:1.8.0_131]
    at java.util.AbstractCollection.toString(Unknown Source) ~[na:1.8.0_131]
    at org.hibernate.collection.internal.PersistentSet.toString(PersistentSet.java:328) ~[hibernate-core-5.3.7.Final.jar:5.3.7.Final]

我猜问题可能出在获取最后一个数组并导致 Whosebug 错误。

编辑：

这个问题是因为 OneToMany 和 ManyToOne 在同一个 SDKCollection class 中，因为它位于层次结构的中间吗？

public class SDKCollection {

       ........
       @JsonIgnore
       @ManyToOne(fetch = FetchType.LAZY)
       @JoinColumn(name = "sdkmaincollection_id")
       private SDKMainCollection sdkcollectionobj;

       @JsonIgnore
       @OneToMany(mappedBy = "sdkcolsubobj", cascade = CascadeType.ALL, fetch=FetchType.LAZY) 
       private Set<Ads> ads;

Answer 1

@JsonIgnore
@OneToMany(mappedBy = "sdkcolsubobj", cascade = CascadeType.ALL, fetch=FetchType.LAZY) 
private Set<Ads> ads

尝试获取=FetchType.EAGER

Answer 2

好吧，您正在使用 @JsonIgnore 注释广告字段，因此当它被序列化以发送回 HTTP 客户端时，Jackson Serializer 将忽略它，因此如果您想包含广告字段，请删除 @JsonIgnore

另一种变通方法是通过@Transaction 注释您的控制器，这样您就不会遇到惰性初始化异常。（fetch=FetchType.EAGER 被认为是不好的做法见 https://vladmihalcea.com/eager-fetching-is-a-code-smell/）

更好的解决方案是使用实体图作为获取计划，它与 Spring DATA 集成得非常好，看看

Answer 3

可能有一个案例。

在你的条件下尝试 fetch=FetchType.EAGER
检查数据库中是否有数据（还有外键关系）。

Answer 4

您缺少 @JsonBackReference 注释，这就是您收到 Whosebug 错误的原因。@JsonIgnore 不是为了解决无限递归问题而设计的，它只是忽略注释属性的序列化或反序列化。

在哪里添加

在SDKCollection.java 私有 SDKMainCollection sdkcollectionobj； 向后引用 SDKMaincollection，
in Ads.java private SDKCollection sdkcolsubobj 向后引用 SDKCollection

以上两者都应使用 @JsonBackReference 进行注释希望对你有帮助。

Answer 5

所以我终于能够解决错误。

因为我有三级层次结构，这是我完成这项工作的唯一方法。

已从 child table 个实体中删除 ManyToOne
仅在 @OneToMany

cascade = CascadeType.ALL,orphanRemoval = true

没有 parent table 是从 child tables

@ManyToOne

所以变化如下

TABLE-1 (SDKMainCollection.java)

@Entity
@Table(name="sdkmaincollection")
public class SDKMainCollection {

...
...
@OneToMany(cascade = CascadeType.ALL,orphanRemoval = true)
private List<Sdkcollection> sdkCollection = new ArrayList<Sdkcollection>();

//No Constructor required
//Kept only getters and setters
}

TABLE-2 (SDKCollection.java)

@Entity
@Table(name="sdkcollection")
public class SDKCollection {

...
...
@OneToMany(cascade = CascadeType.ALL,orphanRemoval = true)
private List<Ads> ads = new ArrayList<Ads>();

//No parent table with @ManyToOne was refered
//No Constructor required
//Kept only getters and setters

}

TABLE-3 (Ads.java)

@Entity
@Table(name="ads")
public class Ads {


...
...
//No parent table with @ManyToOne was refered
//No Constructor required
//Kept only getters and setters

}

Hibernate 为层次结构创建了关系和额外的 table。 Child table 最后一级的详细信息已检索到，没有任何 Whosebuger 错误。

Spring Boot get 请求不使用@OneToMany 获取第三级对象

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