In the JMS Serializer library, the "nested objects policy" refers to how the serialization and deserialization of nested objects are handled. Specifically, it deals with how to handle relationships between objects and how to avoid circular references during serialization.

By default, the JMS Serializer library will serialize nested objects using their full representation, which can lead to circular reference issues. To address this, the library provides various policies to control how nested objects are handled during serialization and deserialization.

Here are some common policies available in the JMS Serializer library:

  1. Exclude Policy: The exclude policy allows you to exclude certain properties or relationships from being serialized. You can use this policy to avoid circular references by excluding the properties that would lead to circularity.

    For example, consider two classes, Author and Book, where an Author has a collection of Book objects, and each Book object has a reference to its Author. To avoid circular references during serialization, you can exclude the Author property from the Book serialization:

    php
    use JMS\Serializer\Annotation as Serializer; class Author { // ... /** * @Serializer\Exclude() */ private $books; } class Book { // ... /** * @Serializer\Exclude() */ private $author; }
  2. Groups Policy: The groups policy allows you to define groups of properties that should be serialized or deserialized together. By using groups, you can control which properties are included in the serialization of a specific context.

    For example, you can define separate groups for serializing Author and Book objects and exclude the circular references from each group:

    php
    use JMS\Serializer\Annotation as Serializer; class Author { // ... /** * @Serializer\Groups({"author_group"}) */ private $books; } class Book { // ... /** * @Serializer\Groups({"book_group"}) */ private $author; }

    Then, during serialization, you can specify the groups to be used:

    php
    $serializer->serialize($author, 'json', SerializationContext::create()->setGroups(['author_group']));
  3. Max Depth Policy: The max depth policy allows you to limit the depth of serialization to avoid deep nesting and circular references. You can set a maximum depth for serialization, and properties beyond that depth will not be included.

    For example, you can limit the depth of serialization to 1 to avoid circular references:

    php
    use JMS\Serializer\Annotation as Serializer; class Author { // ... /** * @Serializer\MaxDepth(1) */ private $books; } class Book { // ... /** * @Serializer\MaxDepth(1) */ private $author; }

By using these policies in combination, you can control how nested objects are handled during serialization and deserialization in the JMS Serializer library, avoiding circular references and optimizing the serialization process.

Have questions or queries?
Get in Touch