Symfony5.4自定义序列化器如何处理属性Context注解？

基于Symfony 5.4开发应用，定义了如下Client类：

class Client
{
    #[Context([DateTimeNormalizer::FORMAT_KEY => 'Y-m-d'])]
    public \DateTimeImmutable $passportIssuedDate;

    #[Context([DateTimeNormalizer::FORMAT_KEY => \DateTimeImmutable::ATOM])]
    public \DateTimeImmutable $agreementDateTime;
}

自定义序列化器代码如下：

$encoders = [new JsonEncoder()];
$extractor = new PropertyInfoExtractor([], [new PhpDocExtractor(), new ReflectionExtractor()]);
$normalizers = [
    new DateTimeNormalizer(),
    new ObjectNormalizer(propertyTypeExtractor: $extractor),
];
$serializer = new Serializer($normalizers, $encoders);

调用自动注入的标准序列化器：

$this->serializer->serialize($client, 'json');

得到正确结果：

{"passportIssuedDate":"2024-04-05","agreementDateTime":"2024-04-05T11:59:32+00:00"}

但使用自定义序列化器时，结果为：

{"passportIssuedDate":"2024-04-05T11:59:32+00:00","agreementDateTime":"2024-04-05T11:59:32+00:00"}

需修改自定义序列化器，使其正确处理属性的Context注解。

自定义序列化器未识别Context注解，是因为ObjectNormalizer缺少读取注解元数据的能力。需添加注解读取相关组件，让序列化器能解析并应用属性上的Context配置。

修改后的自定义序列化器代码如下：

use Symfony\Component\Serializer\Encoder\JsonEncoder;
use Symfony\Component\Serializer\Normalizer\DateTimeNormalizer;
use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;
use Symfony\Component\Serializer\Serializer;
use Symfony\Component\PropertyInfo\Extractor\PhpDocExtractor;
use Symfony\Component\PropertyInfo\Extractor\ReflectionExtractor;
use Symfony\Component\PropertyInfo\PropertyInfoExtractor;
use Symfony\Component\Serializer\Mapping\Factory\ClassMetadataFactory;
use Symfony\Component\Serializer\Mapping\Loader\AnnotationLoader;
use Doctrine\Common\Annotations\AnnotationReader;
use Symfony\Component\Serializer\Mapping\AttributeMetadataFactory\ContextAwareAttributeMetadataFactory;

// 1. 构建注解读取器与类元数据工厂，用于读取属性上的Context注解
$classMetadataFactory = new ClassMetadataFactory(
    new AnnotationLoader(new AnnotationReader())
);

// 2. 包装元数据工厂，使其能解析Context注解并转化为序列化上下文配置
$contextAwareMetadataFactory = new ContextAwareAttributeMetadataFactory(
    $classMetadataFactory
);

$encoders = [new JsonEncoder()];
$extractor = new PropertyInfoExtractor([], [new PhpDocExtractor(), new ReflectionExtractor()]);
$normalizers = [
    new DateTimeNormalizer(),
    // 3. 给ObjectNormalizer传入支持Context注解的元数据工厂
    new ObjectNormalizer(
        classMetadataFactory: $contextAwareMetadataFactory,
        propertyTypeExtractor: $extractor
    ),
];
$serializer = new Serializer($normalizers, $encoders);

核心逻辑说明： #

• ClassMetadataFactory + AnnotationLoader + AnnotationReader组合，负责扫描类和属性上的序列化注解；
• ContextAwareAttributeMetadataFactory会将属性上的Context注解内容，转化为序列化时的上下文参数；
• 给ObjectNormalizer传入上述元数据工厂后，序列化过程中就能根据每个属性的Context注解，应用对应的日期格式化规则。

内容的提问来源于stack exchange，提问作者Andrew Markhai