php – Doctrine 2坚持在ManyToOne关系中保持已经管理的实体

当我想将新人保留到数据库时,我创建一个Person对象并尝试将其Department属性设置为由Entity Manager管理的现有Department对象.但是,当我尝试坚持我的新Person时,我得到一个例外：

A new entity was found through the relationship
‘Entities\Person#department’ that was not configured to cascade
persist operations for entity:
Entities\Department@0000000016abe202000000000d29dd37. To solve this
issue: Either explicitly call EntityManager#persist() on this unkNown
entity or configure cascade persist this association in the mapping
for example @ManyToOne(..,cascade={“persist”}).

我并不完全理解异常部分,该部门称该部门是一个“未知实体”,因为我是通过实体经理提取的.

如异常所示,我在yml元数据中插入了一个级联(cascade：[“persist”]).我的人然后得到了保存,但我最终在department表中有了一个重复的部门,并带有一个新的id.

这必须是一个非常常见的用例.我在下面提供了我的代码和元数据.我应该做些什么改变？

元数据：

Entities\Person
  type: entity
  table: people
  fields:
    ...
    departmentId:
      type: integer
      unsigned: false
      nullable: false
      column: department_id
    ...
  manyToOne:
    department:
      targetEntity: Entities\Department
      joinColumn: department_id
      referenceColumnName: id

码：

$department = $em->getRepository('Department')->findOneBy(array('name' => $departmentName);

$person = new Person();
$person->setName('Joe Bloggs');
$person->setDepartment($department);

$em->persist($person);
$em->flush();