Doctrine return null in place of EntityNotFoundException

问题

I have broken FKs in my database and if I load an entity and ask for a related entity Doctrine will throw \Doctrine\ORM\EntityNotFoundException.

For the entity in question, I would prefer that where the FK is broken it would return NULL rather than throw an exception. This is because its within a Twig template that the exception occurs and I would prefer Twig to not have to have to handle the exception in this case.

The following is an example configuration.

<?xml version="1.0" encoding="utf-8"?>
<doctrine-mapping xmlns="http://doctrine-project.org/schemas/orm/doctrine-mapping"
                  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                  xsi:schemaLocation="http://doctrine-project.org/schemas/orm/doctrine-mapping http://doctrine-project.org/schemas/orm/doctrine-mapping.xsd">
    <entity name="Foo\Click" table="clicks">
        <id name="id" type="bigint" column="click_id">
            <generator strategy="IDENTITY"/>
        </id>
        <!-- .. -->
        <many-to-one field="visitor" target-entity="Foo\Visitor" fetch="LAZY">
            <join-columns>
                <join-column name="visitor_id" referenced-column-name="visitor_id"/>
            </join-columns>
        </many-to-one>
    </entity>

    <entity name="Foo\Visitor" table="visitors" read-only="true">
        <id name="visitorId" type="integer" column="visitor_id">
            <generator strategy="IDENTITY"/>
        </id>
        <!-- ... -->
        <one-to-one field="firstClick" target-entity="Foo\Click" fetch="LAZY">
            <join-columns>
                <join-column name="click_id" referenced-column-name="click_id"/>
            </join-columns>
        </one-to-one>
    </entity>
</doctrine-mapping>

The following is an example of expected results where the the click as a visitor ID, but the a visitor record does not exists with that ID. In this case, I would rather not have to wrap the logic in Try/Catch and instead have Click::getVisitor() return null;

<?php
$clickOne = $entityManager()->find(Foo\Click::class, 1);
$v = $clickOne->getVisitor();

if ($v !== null) {
    echo $v->getId(); // may throw Doctrine\ORM\EntityNotFoundException
}

Is there a strategy for this with Doctrine?

Update: Added example configuration and code, and now I see the why this is not achievable with a simple Doctrine configuration.

回答1:

EntityNotFoundException is thrown from Doctrine's proxy. So you can use EAGER loading method to get rid of proxies and get NULL instead of exception.

回答2:

This is the strategy I have adopted based on the comment made by iainn.

<?php
class Parent
{
    protected $child;

    public function getChild()
    {
        if ($this->child instance of \Doctrine\ORM\Proxy\Proxy) {
            try {
                $this->child->__load();
            } catch (\Doctrine\ORM\EntityNotFoundException $e) {
                $this->child = null
            }
        }

        return $this->child;
    }
}

I am sure it is not recommended for your entities to interact directly with proxies. But I preferred this over calling a known method on the entity (which would also have the effect of loading it) because the intention of this code is clearer to the next developer who might read it.

I'm not sure if there are any side effects with interacting with the proxy like this.

来源：https://stackoverflow.com/questions/51893358/doctrine-return-null-in-place-of-entitynotfoundexception

标签

php

doctrine-orm

entity