Question

存在两个实体Permission和Role，它们之间的关系为@ManyToMany；我想在他们的联接表中添加一些额外的字段，并按照本文enter link description here进行了编码，这是我的代码：
角色实体

@Setter
@Getter
@AllArgsConstructor
@NoArgsConstructor
@Entity
@GenericGenerator(name = "jpa-uuid", strategy = "uuid")
public class Role {

    @Id
    @GeneratedValue(generator = "jpa-uuid")
    private String id;

    @JsonIgnore @ToString.Exclude
    @OneToMany(mappedBy = "role",cascade = CascadeType.ALL,orphanRemoval = false,fetch = FetchType.EAGER)
    private Set<RolePermission> role_permission;

    public void addPermission(Permission permission){
        RolePermission rolePermission  = new RolePermission(this,permission);
        role_permission.add(rolePermission);
        permission.getRole_permission().add(rolePermission);
    }
    public void removePermission(Permission permission){
        for(Iterator<RolePermission> iterator = role_permission.iterator();iterator.hasNext();){
            RolePermission rolePermission = iterator.next();
            if(rolePermission.getRole().equals(this) && rolePermission.getPermission().equals(permission)){
                iterator.remove();
                rolePermission.getRole().role_permission.remove(rolePermission);
                rolePermission.setRole(null);
                rolePermission.setPermission(null);
            }
        }
    }


    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Role role = (Role) o;
        return Objects.equals(id, role.id);
    }

    @Override
    public int hashCode() {
        return Objects.hash(id);
    }
}

权限实体


@Setter
@Getter
@AllArgsConstructor
@NoArgsConstructor
@Entity
@GenericGenerator(name = "jpa-uuid", strategy = "uuid")
public class Permission {
    @Id
    @GeneratedValue(generator = "jpa-uuid")
    private String id;

    @JsonIgnore @ToString.Exclude
    @OneToMany(mappedBy = "permission",cascade = CascadeType.ALL,orphanRemoval = true,fetch = FetchType.EAGER)
    private Set<RolePermission> role_permission;

    public void addRole(Role role){
        RolePermission rolePermission  = new RolePermission(role,this);
        role_permission.add(rolePermission);
        role.getRole_permission().add(rolePermission);
    }
    public void removeRole(Role role){
        for(Iterator<RolePermission> iterator = role_permission.iterator(); iterator.hasNext();){
            RolePermission rolePermission = iterator.next();
            if(rolePermission.getRole().equals(role) && rolePermission.getPermission().equals(this)){
                iterator.remove();
                rolePermission.getRole().getRole_permission().remove(rolePermission);
                rolePermission.setRole(null);
                rolePermission.setPermission(null);
            }
        }
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Permission that = (Permission) o;
        return Objects.equals(id, that.id);
    }

    @Override
    public int hashCode() {
        return Objects.hash(id);
    }
}

角色权限密钥


@Embeddable
@Setter
@Getter
@NoArgsConstructor
public class RolePermissionKey implements Serializable {
    private static final long serialVersionUID = 4686642987484483168L;
    @Column(name = "role_id")
    private String role_id;
    @Column(name = "permission_id")
    private String permission_id;

    public RolePermissionKey(String roleId, String permissionId) {
        this.role_id=roleId;
        this.permission_id=permissionId;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        RolePermissionKey that = (RolePermissionKey) o;
        return role_id.equals(that.role_id) &&
                permission_id.equals(that.permission_id);
    }

    @Override
    public int hashCode() {
        return Objects.hash(role_id, permission_id);
    }
}

具有额外字段的关系表

@Entity
@Setter
@Getter
@NoArgsConstructor
public class RolePermission implements Serializable {
    private static final long serialVersionUID = 8274025418699729303L;

    @EmbeddedId
    RolePermissionKey id;

    @ManyToOne(fetch = FetchType.LAZY)
    @MapsId("role_id")
    Role role;

    @ManyToOne(fetch = FetchType.LAZY)
    @MapsId("permission_id")
    Permission permission;

    Date create_date  =new Date();


    public RolePermission(Role role,Permission permission) {
        this.role=role;
        this.permission=permission;
        this.id = new RolePermissionKey(role.getId(),permission.getId());
        this.create_date=new Date();
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        RolePermission that = (RolePermission) o;
        return Objects.equals(role, that.role) &&
                Objects.equals(permission, that.permission);
    }

    @Override
    public int hashCode() {
        return Objects.hash(role, permission);
    }
}

测试代码

        Role role5 = roleRepository.findByTitle("Role5");
        Permission permission6 = permissionRepository.findByTitle("Permission6");
        role5.addPermission(permission6);
        permission6.addRole(role5);
        roleRepository.save(role5);
        permissionRepository.save(permission6);

然后，我在四个地方使用了相同的测试代码进行测试：
1。一个类实现ApplicationRunner；在Spring Boot启动之前初始化数据no exception
2。春季启动测试类@SpringBootTest; no exception
3。控制器类@Controller; exception thrown
4。服务类@Service; exception thrown
例外： 2020-05-05 09:11:35.952 WARN 17000 --- [nio-8080-exec-1] .m.m.a.ExceptionHandlerExceptionResolver : Resolved [org.springframework.dao.DataIntegrityViolationException: A different object with the same identifier value was already associated with the session : [com.xxx.model.authentication.RolePermission#com.xxx.model.authentication.RolePermissionKey@9e2c8771]; nested exception is javax.persistence.EntityExistsException: A different object with the same identifier value was already associated with the session : [com.xxx.model.authentication.RolePermission#com.xxx.model.authentication.RolePermissionKey@9e2c8771]]
现在我很困惑问题是代码还是其他。我在1,2中使用测试代码在一个角色和一个权限被成功地获得了预期的结果。但是代码在3,4中不起作用。
我需要一些提示和建议；顺便说一句，是否有任何值得学习的使用spring数据jpa的开源现实世界项目，谢谢。

#################################################################
感谢@ Olivier Depriester的帮助。我已经在调试模型中研究了RolePermission和Permission Entity中RolePermission Set的元素；保持两个实体之间关系的集合类型为set，我已经覆盖了equals()和可以确保具有相同ID的关系实体（RolePermission）不会出现在同一集合中的hashCode()方法。在save()执行之前，“角色和权限集”中实际上只包含一个RolePermission对象。在测试代码中，有两个.save()操作，即使我注释了其中之一，也会抛出异常。我想知道cascade是否存在问题。可以在某个地方成功执行测试代码很奇怪。

Answer 1

呼叫role5.get().addPermission(permission6);时，会为RolePermission和role5创建并保留（*）permission6。

呼叫permission6.addRole(role5);时，将为RolePermission和role5创建并保留另一个permission6。

==>例外：会话中具有相同哈希码的同一实体的2个实例。

（*）将项目添加到持久对象的属性时，该项目将自动持久化。当您从存储库中获得role5和permission6时，它们就是持久对象

因此，您需要修改代码以创建1个单独的RolePermission，可以将其分配给Role和Permission

春季启动数据jpa DataIntegrityViolationException EntityExistsException

1 个答案: