Symfony 3 Doctrine 2：关于关系的循环引用

Question

我正在尝试使用 Doctrine 2 在 Symfony 3 中使用 4 个实体，但是当我想序列化 Account 实体时遇到循环引用异常：

检测到循环引用（配置限制：1）。

我在实体中选择了双向关系，架构是这样的：

 - Account [1] ---- [0..*] AccountSheet
 - AccountSheet [1] ---- [0..*] Operation
 - Operation [0..*] ---- [1] Category

这里是实体（为了清楚起见，做了一些清洁）：

src\AppBundle\Entity\Account.php

<?php
    namespace AppBundle\Entity;

    use Doctrine\ORM\Mapping as ORM;
    use Doctrine\Common\Collections\ArrayCollection;
    use AppBundle\Entity\AbstractGenericEntity;

    /**
     * @ORM\Entity()
     * @ORM\Table(name="accounts",
     *      uniqueConstraints={@ORM\UniqueConstraint(name="accounts_name_unique",columns={"name"})})
     */
    class Account extends AbstractGenericEntity{
        /**
         * @ORM\OneToMany(targetEntity="AccountSheet", mappedBy="account")
         * @var AccountSheet[]
         */
        protected $accountSheets;

        public function __construct($name = null, $description = null){
            $this->accountSheets = new ArrayCollection();
            $this->name = $name;
            $this->description = $description;
        }
    }

src\AppBundle\Entity\AccountSheet.php

<?php
    namespace AppBundle\Entity;

    use Doctrine\ORM\Mapping as ORM;
    use Doctrine\Common\Collections\ArrayCollection;
    use AppBundle\Entity\AbstractGenericEntity;

    /**
     * @ORM\Entity()
     * @ORM\Table(name="accounts_sheets",
     *      uniqueConstraints={@ORM\UniqueConstraint(name="accountsheet_account_unique", columns={"name", "account_id"})})
     * @ORM\HasLifecycleCallbacks
     */
    class AccountSheet extends AbstractGenericEntity{

        /**
         * @ORM\ManyToOne(targetEntity="AppBundle\Entity\Account", inversedBy="accountSheets")
         * @var Account
         */
        protected $account;

        /**
         * @ORM\OneToMany(targetEntity="Operation", mappedBy="accountSheet")
         * @var Operation[]
         */
        protected $operations;

        public function __construct($name = null){
             $this->operations = new ArrayCollection();
             $this->name = $name;
        }
    }

src\AppBundle\Entity\Operation.php

<?php
    namespace AppBundle\Entity;

    use Doctrine\ORM\Mapping as ORM;
    use AppBundle\Entity\AbstractGenericEntity;

    /**
     * @ORM\Entity()
     * @ORM\Table(name="operations")
     */
    class Operation extends AbstractGenericEntity{
        /**
         * @ORM\ManyToOne(targetEntity="AppBundle\Entity\AccountSheet", inversedBy="operations")
         * @ORM\JoinColumn(nullable=false)
         * @var AccountSheet
         */
        protected $accountSheet;

        /**
         * @ORM\ManyToOne(targetEntity="AppBundle\Entity\Category", inversedBy="operations")
         * @var Category
         */
        protected $category;

        public function __construct($type = null, $label = null, $montant = null, $comment = null){
            $this->label = $label;
            $this->type = $type;
            $this->comment = $comment;
            $this->montant = $montant;
        }
    }

src\AppBundle\Entity\Category.php

<?php
    namespace AppBundle\Entity;

    use Doctrine\ORM\Mapping as ORM;
    use Doctrine\Common\Collections\ArrayCollection;
    use AppBundle\Entity\AbstractGenericEntity;

    /**
     * @ORM\Entity()
     * @ORM\Table(name="categories")
     */
    class Category extends AbstractGenericEntity{

        /**
         * @ORM\Column(type="string")
         */
        protected $label;

        /**
         * @ORM\Column(type="string")
         */
        protected $description;

        /**
         * @ORM\OneToMany(targetEntity="Operation", mappedBy="category")
         * @var Operation[]
         */
        protected $operations;

        public function __construct($name = null){
            $this->operations = new ArrayCollection();
            $this->name = $name;
        }
}

我猜它在 Operation 实体上，其中 AccountSheet 再次被引用。双向 on 操作并不是真正需要的。

我该如何重新安排呢？

谢谢！

Answer 1

来自官方文档：

循环引用在处理实体关系时很常见

为避免无限循环，GetSetMethodNormalizer 在遇到这种情况时会抛出 CircularReferenceException：

$member = new Member();
$member->setName('Kévin');

$org = new Organization();
$org->setName('Les-Tilleuls.coop');
$org->setMembers(array($member));

$member->setOrganization($org);

echo $serializer->serialize($org, 'json'); // Throws a CircularReferenceException

所以，从这一点开始，你有 3 个解决方案来解决这个问题：

1. 设置循环引用处理程序：

除了抛出异常之外，循环引用也可以由自定义可调用对象处理。这在序列化具有唯一标识符的实体时特别有用：

$encoder = new JsonEncoder();
$normalizer = new ObjectNormalizer();

$normalizer->setCircularReferenceHandler(function ($object) {
    return $object->getName();
});

$serializer = new Serializer(array($normalizer), array($encoder));
var_dump($serializer->serialize($org, 'json'));
// {"name":"Les-Tilleuls.coop","members":[{"name":"K\u00e9vin", organization: "Les-Tilleuls.coop"}]}

1. 设置忽略的属性（不是我的首选解决方案）：

在你的情况下：

$encoder = new JsonEncoder();
$normalizer = new ObjectNormalizer();

normalizer->setIgnoredAttributes(array("account", "accountSheet", "category", "operation"));

$serializer = new Serializer(array($normalizer), array($encoder));
var_dump($serializer->serialize($org, 'json'));

1. 使用组属性（我的首选解决方案）： 此方法类似于设置忽略的属性，因为您将通过在其上添加组注释来选择要序列化的属性，其余的将在规范化过程中被忽略以进行递归。

Using Serialization Groups Annotations

Attributes Groups

在您使用 Account 实体的情况下，例如在帐户方面执行此操作：

<?php
namespace AppBundle\Entity;

use Doctrine\ORM\Mapping as ORM;
use Doctrine\Common\Collections\ArrayCollection;
use AppBundle\Entity\AbstractGenericEntity;
use Symfony\Component\Serializer\Annotation\Groups;

/**
 * @ORM\Entity()
 * @ORM\Table(name="accounts",
 *      uniqueConstraints={@ORM\UniqueConstraint(name="accounts_name_unique",columns={"name"})})
 */
class Account extends AbstractGenericEntity{
    /**
     * @ORM\OneToMany(targetEntity="AccountSheet", mappedBy="account")
     * @var AccountSheet[]
     * @Groups({"account"})
     */
    protected $accountSheets;

    public function __construct($name = null, $description = null){
        $this->accountSheets = new ArrayCollection();
        $this->name = $name;
        $this->description = $description;
    }
}

那就不要在 AccountSheet 实体的 $account 字段上加上这个组注解，以摆脱循环引用的问题。

最后你序列化你的帐户：

$encoder = new JsonEncoder();
$normalizer = new ObjectNormalizer();

$serializer = new Serializer(array($normalizer), array($encoder));
var_dump($serializer->serialize($account, 'json', array('groups' => array('account')) ));

Answer 2

$jsonContent = $serializer->serialize($yourObject, 'json', [
    'circular_reference_handler' => function ($object) {
        return $object->getId();
    }
]);

上面的代码适用于我修复循环引用异常。 (Symfony >=4.2)