[[serializers]]
== Serializers

The client has three serializers available. You will most likely never need
to change the serializer, unless you have special requirements or are 
implementing a new protocol.

The job of the serializer is to encode the outgoing request body and decode the 
incoming response body. In 99% of cases, this is a simple conversion to/from 
JSON.

The default serializer is the `SmartSerializer`.


=== SmartSerializer

==== Serialize()

The `SmartSerializer` inspects the data to be encoded. If the request body is 
provided as a string, it is passed directly to {es} as a string. This allows 
users to provide raw JSON, or raw strings for certain endpoints that don't have 
structure (such as the Analyze endpoint).

If the data is an array, it is converted to JSON. If the data provided was an
empty array, the serializer manually converts the JSON from an empty array 
(`[]`) to an empty object (`{}`) so that it is valid JSON for {es} request 
bodies.

==== Deserialize()

When decoding the response body, the `SmartSerializer` introspects the 
`content_type` headers to determine the appropriate encoding. If the data is
encoded as JSON, it is decoded into an array using `json_decode`. Otherwise, it 
is returned as a string.

This functionality is required to cooperate with endpoints such as the `Cat` 
endpoints, which return tabular text instead of JSON.


==== Selecting the SmartSerializer

The `SmartSerializer` is selected by default, but if you wish to manually 
configure it for explicitness, you can do so by using the `setSerializer()` 
method on the `ClientBuilder` object:

[source,php]
----
$client = ClientBuilder::create()
            ->setSerializer('\Elasticsearch\Serializers\SmartSerializer');
            ->build();
----

Note that the serializer is configured by specifying a namespace path to the 
serializer.


=== ArrayToJSONSerializer

==== Serialize()

The `ArrayToJSONSerializer` inspects the data to be encoded. If the request body
is provided as a string, it is passed directly to {es} as a string. This allows 
users to provide raw JSON, or raw strings for certain endpoints that don't have 
structure (such as the Analyze endpoint).

If the data is an array, it is converted to json. If the data provided was an
empty array, the serializer manually converts the JSON from an empty array 
(`[]`) to an empty object (`{}`) so that it is valid JSON for {es} request 
bodies.


==== Deserialize()

When decoding the response body, everything is decoded to JSON from JSON. If the 
data is not valid JSON, `null` will be returned.


==== Selecting the ArrayToJSONSerializer

You can select `ArrayToJSONSerializer` by using the `setSerializer()` method on 
the `ClientBuilder` object:


[source,php]
----
$client = ClientBuilder::create()
            ->setSerializer('\Elasticsearch\Serializers\ArrayToJSONSerializer');
            ->build();
----

Note that the serializer is configured by specifying a namespace path to the 
serializer.


=== EverythingToJSONSerializer

==== Serialize()

The `EverythingToJSONSerializer` tries to convert everything to JSON.

If the data provided was an empty array, the serializer manually converts the 
JSON from an empty array (`[]`) to an empty object (`{}`) so that it is valid
JSON for Elasticsearch request bodies.

If the data was not an array and/or not convertible to JSON, the method returns
`null`.

==== Deserialize()

When decoding the response body, everything is decoded to JSON from JSON. If the 
data is not valid JSON, `null` is returned.

==== Selecting the EverythingToJSONSerializer

You can select  `EverythingToJSONSerializer` by using the `setSerializer()` 
method on the ClientBuilder object:

[source,php]
----
$client = ClientBuilder::create()
            ->setSerializer('\Elasticsearch\Serializers\EverythingToJSONSerializer');
            ->build();
----

Note that the serializer is configured by specifying a namespace path to the 
serializer.

=== Implementing your own Serializer

If you want to use your own custom serializer, you need to implement the 
`SerializerInterface` interface. Please keep in mind that the client uses a 
single Serializer object for all endpoints and all connections.


[source,php]
----
class MyCustomSerializer implements SerializerInterface
{

    /**
     * Serialize request body
     *
     * @param string|array $data Request body
     *
     * @return string
     */
    public function serialize($data)
    {
        // code here
    }

    /**
     * Deserialize response body
     *
     * @param string $data Response body
     * @param array  $headers Response Headers
     *
     * @return array|string
     */
    public function deserialize($data, $headers)
    {
        // code here
    }
}
----
{zwsp} +

To then use your custom serializer, you can specify the namespace path in the 
`setSerializer()` method of the `ClientBuilder` object:

[source,php]
----
$client = ClientBuilder::create()
            ->setSerializer('\MyProject\Serializers\MyCustomSerializer');
            ->build();
----

Alternatively, if your serializer has a constructor or further initialization 
that should occur before given to the client, you can instantiate an object and 
provide that instead:

[source,php]
----
$mySerializer = new MyCustomSerializer($a, $b, $c);
$mySerializer->setFoo("bar");

$client = ClientBuilder::create()
            ->setSerializer($mySerializer);
            ->build();
----