Question

我在https://examples.javacodegeeks.com/enterprise-java/jpa/one-to-many-unidirectional-mapping-in-jpa/

中解释了在用户与角色实体之间实现单向OneToMany

UserDataImpl.java：

@Entity
public class UserDataImpl {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    .
    .
    .

    @OneToMany(targetEntity = RoleDataImpl.class, cascade = CascadeType.ALL, orphanRemoval = true)
    @JoinTable(name = "user_roles", joinColumns = @JoinColumn(name = "user_role_id"), inverseJoinColumns = @JoinColumn(name = "role_id"))
    private Set<Role> roles = new HashSet<>();

    //Constructors
    //Getters and setters
    //Hashcode and equals
    //toString
}

RoleDataImpl.java：

@Entity
public class RoleDataImpl {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    private String name;
    private byte permissionsInByte = 0;

    //Constructors
    //Getters and setters
    //Hashcode and equals
    //toString
}

我的UserRepository和RoleRepository都扩展了JpaRepository。我在保存之前创建了一个用户对象并将一个Role对象附加到它。

我在Spring Data JPA中保存用户时出现以下错误：

org.springframework.dao.InvalidDataAccessApiUsageException: detached entity passed to persist: com.entity.impl.RoleDataImpl; nested exception is org.hibernate.PersistentObjectException: detached entity passed to persist: com.entity.impl.RoleDataImpl
    .
    .

Caused by: org.hibernate.PersistentObjectException: detached entity passed to persist: com.wehub.entity.impl.RoleDataImpl
    at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:124)
    at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:765)
    at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:758)
    .
    .

当我删除orphanRemoval和cascades时：

    @OneToMany(targetEntity = RoleDataImpl.class)
    @JoinTable(name = "user_roles", joinColumns = @JoinColumn(name = "user_role_id"), inverseJoinColumns = @JoinColumn(name = "role_id"))
    private Set<Role> roles = new HashSet<>();

我得到DataIntegrityException（第一个对象正常保存）。因为user_roles表中的role_id将对其具有唯一约束。但是我希望在删除用户时删除user_roles条目。请帮忙。

Answer 1

异常消息告诉您错误：传递给persist的分离实体：com.entity.impl.RoleDataImpl 这意味着您的#include <Windows.h> #include <GL\glew.h> #include <GL\freeglut.h> class Test { public: Test() { } void enable(); }; void Test::enable() { //glEnable(GL_DEPTH_TEST); // Doesn't compile? Error - Error C2146 syntax error: missing ';' } int main() { glEnable(GL_DEPTH_TEST); }实例拥有对{{User的引用1}}反过来不由您的Role管理。

它应该像这样工作：

EntityManager

单向OneToMany关系引发UniqueConstraint

1 个答案: