Symfony实体未配置为级联

Question

任何人都可以帮我解释我做错了吗？我尝试设置一个与文件相关的实体。它涉及供应商和库存。

我的股票实体看起来像

/**
 * @ORM\ManyToOne(targetEntity="PrClientBundle\Entity\Lieferanten")
 * @ORM\JoinColumn(name="liefer_id", referencedColumnName="id")
 * @var lieferant
 */
private $lieferant;

我也使用getter和setter，如下面的

    /**
 * Set lieferant
 *
 * @param \PrClientBundle\Entity\Lieferanten $lieferant
 * @return Leadbase
 */
public function setLieferant(\PrClientBundle\Entity\Lieferanten $lieferant = null)
{
    $this->lieferant = $lieferant;

    return $this;
}

/**
 * Get lieferant
 *
 * @return \PrClientBundle\Entity\Lieferanten 
 */
public function getLieferant()
{
    return $this->lieferant;
}

当我导入新的Stockitems时：

$lead->setLieferant($lieferant);

我收到以下错误消息，我真的不明白:(

[Doctrine\ORM\ORMInvalidArgumentException]                                                                                                                                      
  A new entity was found through the relationship 'PrLeadBundle\Entity\Leadbase#lieferant' that was not configured to cascade persist operations for entity: PrClientBundle\Enti  
  ty\Lieferanten@000000002a45dae80000000002f826ff. 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"}). If you cannot find out which entity causes the problem implement 'PrClientBundle\Entity\Lieferante  
  n#__toString()' to get a clue.  

如果你能帮助我理解我做错了什么，那将是非常好的。