Question

我的无限递归问题非常烦人。我的应用程序正在构建为Spring Rest API，我使用Lombok生成构造函数和getter以及setter。我的模特很少。

AppUser - 可能是最大的一个。

@NoArgsConstructor
@AllArgsConstructor
@Data
@Entity
public class AppUser {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String login;
    private String name;
    private String surname;
    @JsonProperty(access = JsonProperty.Access.WRITE_ONLY)
    private String password;

    public AppUser(String login, String password, UserRole userRole) {
        this.login = login;
        this.password = password;
        this.userRoleSet = new HashSet<>();
        this.userRoleSet.add(userRole);
    }

    public AppUser(String login, String name, String surname, String password) {
        this.login = login;
        this.name = name;
        this.surname = surname;
        this.password = password;
    }

    @OneToMany(mappedBy = "appUser",fetch = FetchType.EAGER)
    private Set<UserRole> userRoleSet;

    @OneToMany(mappedBy = "createdBy")
    private List<Incident> createdIncidentsList;

    @OneToMany(mappedBy = "assignedTo")
    private List<Incident> assignedToIncidentsList;

    @OneToMany(mappedBy = "postedBy")
    private List<Comment> commentList;

    @OneToMany(mappedBy = "appUser")
    private List<IncidentChange> incidentChangeList;

}

事件

@Data
@Entity
public class Incident {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String title;
    private String description;
    private LocalDateTime creationDate;
    private IncidentStatus status;

    @OneToMany(mappedBy = "incident", cascade = CascadeType.ALL)
    private List<Comment> commentList;
    @ManyToOne
    private AppUser createdBy;
    @ManyToOne
    private AppUser assignedTo;
    @OneToOne(cascade = CascadeType.ALL)
    private ChangeLog changeLog;

    public Incident(String title, String description) {
        this.title = title;
        this.description = description;
        this.creationDate = LocalDateTime.now();
        this.status = IncidentStatus.NEW;
        this.commentList = new ArrayList<>();
        this.changeLog = new ChangeLog();
    }
    public Incident(){

    }
    public Incident(String title, String description, LocalDateTime creationDate, IncidentStatus status, List<Comment> commentList, AppUser assignedTo, AppUser createdBy, ChangeLog changeLog) {
        this.title = title;
        this.description = description;
        this.creationDate = creationDate;
        this.status = status;
        this.commentList = commentList;
        this.changeLog = changeLog;
    }

}

注释

@Data
@NoArgsConstructor
@Entity
public class Comment {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String description;
    private LocalDateTime creationDate;

    @ManyToOne
    private AppUser postedBy;
    @ManyToOne
    private Incident incident;

}

修改记录

@Data
@Entity
public class ChangeLog {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @OneToOne
    private Incident incident;
    @OneToMany(mappedBy = "changeLog")
    private List<IncidentChange> incidentChangeList;

    public ChangeLog(){
        this.incidentChangeList = new ArrayList<>();
    }

    public ChangeLog(Incident incident, List<IncidentChange> incidentChangeList) {
        this.incident = incident;
        this.incidentChangeList = incidentChangeList;
    }

}

IncidentChange

@Data
@NoArgsConstructor
@Entity
public class IncidentChange {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String description;
    private LocalDateTime changeDate;

    @ManyToOne
    private ChangeLog changeLog;
    @ManyToOne
    private AppUser appUser;
}

简而言之就是这样：

AppUser与事件，评论和事件变更有一个关系。

事件与AppUser有很多关系（TWICE很重要），
OneToMany评论，
OneToOne to ChangeLog

评论与AppUser有很多关系，
ManyToOne事件发生

ChangeLog具有与事件的OneToOne关系，
OneToMany to IncidentChange

IncidentChange具有与ChangeLog的ManyToOne关系，
ManyToOne到AppUser

我知道AppUser处于事件状态，并且在Comment中嵌套在Incident中，与IncidentChange相同，但它的嵌套更深。

以下是想要检查如何创建AppUser和突发事件的人员的代码https://bitbucket.org/StabloPL/backendsimpleticketsystem/src/76e6bd107e68c82614fbc040b95f041fd7f51d28/src/main/java/com/djagiellowicz/ticketsystem/backendsimpleticketsystem/model/?at=master IncidentController，AppUserControler和IncidentService，AppUserService都是可能让人感兴趣的东西。

当我创建用户（通过Postman作为JSON），之后我获取它，没有问题一切正常。当我创建事件并将其分配给特定的人时，我无法获取事件，也无法获取此特定用户。其他页面，其中没有创建事件的用户获取没有任何问题。这同样适用于未分配createdBy用户的事件。一切都保存到数据库，没有任何问题。

当我尝试获取事件时，Hibernate / Spring抛出了这个错误。当然有点削减。

java.lang.IllegalStateException: Cannot call sendError() after the response has been committed
    at org.apache.catalina.connector.ResponseFacade.sendError(ResponseFacade.java:472) ~[tomcat-embed-core-8.5.29.jar:8.5.29]
    at javax.servlet.http.HttpServletResponseWrapper.sendError(HttpServletResponseWrapper.java:129) ~[tomcat-embed-core-8.5.29.jar:8.5.29]
    at javax.servlet.http.HttpServletResponseWrapper.sendError(HttpServletResponseWrapper.java:129) ~[tomcat-embed-core-8.5.29.jar:8.5.29]


2018-04-24 11:39:43.731 ERROR 18300 --- [nio-8080-exec-4] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: Infinite recursion (StackOverflowError); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Infinite recursion (StackOverflowError) (through reference chain: com.djagiellowicz.ticketsystem.backendsimpleticketsystem.model.AppUser["createdIncidentsList"]->org.hibernate.collection.internal.PersistentBag[0]->com.djagiellowicz.ticketsystem.backendsimpleticketsystem.model.Incident["createdBy"]->com.djagiellowicz.ticketsystem.backendsimpleticketsystem.model.AppUser["createdIncidentsList"]->org.hibernate.collection.internal.PersistentBag[0]->
java.lang.StackOverflowError: null

我该如何解决？我必须知道AppUser发布了哪条评论，同样适用于Incident和IncidentChange，我不想从Incident / IncidentChange / Comment

中删除这些信息

Answer 1

您必须覆盖Lombok的注释...当您使用@Data时，您隐式使用类中的所有字段调用@EqualsAndHashCode。无限递归从您用于映射关系的字段中引发。每个类中@EqualsAndHashCode以排除集合字段。例如，您可以在AppUser类上添加annotatio @EqualsAndHashCode(exclude={"userRoleSet", "createdIncidentsList","assignedToIncidentsList","commentList","incidentChangeList"})以覆盖@Data默认策略。您必须在每个模型类上执行此操作，直到没有无限递归错误。

此外......您的类之间存在循环依赖关系。序列化对象时，应删除所有循环依赖项。最好的解决方案是序列化DTO而不是实体。创建没有循环依赖关系的DTO应该可以解决这个问题。在序列化/反序列化中，您可以使用包含事件列表的AppUserDTO，一个不带AppUser参考的IncidentDTO列表。

Answer 2

您可以将@JsonIgnore注释放在您不希望包含在JSON中的字段中。

如果您想要更灵活，可以使用@JsonView注释。

您还可以使用@JsonManagedReference和@JsonBackReference。

您使用的是由您自己决定的。如果您真的不需要前端的属性，我建议您使用@JsonIgnore。如果在某种情况下您可能需要一个属性而不是另一个属性，我会使用@JsonView。

Hibernate：无限递归，如何解决？

2 个答案: