#### Message Codecs

You can send any object you like across the event bus if you define and register a `message codec` for it.

Message codecs have a name and you specify that name in the `DeliveryOptions` when sending or publishing the message:

    eventBus.registerCodec(myCodec);

    DeliveryOptions options = new DeliveryOptions().setCodecName(myCodec.name());

    eventBus.send("orders", new MyPOJO(), options);

If you always want the same codec to be used for a particular type then you can register a default codec for it, then you don’t have to specify the codec on each send in the delivery options:

    eventBus.registerDefaultCodec(MyPOJO.class, myCodec);

    eventBus.send("orders", new MyPOJO());

You unregister a message codec with `unregisterCodec`.

Message codecs don’t always have to encode and decode as the same type. For example you can write a codec that allows a MyPOJO class to be sent, but when that message is sent to a handler it arrives as a MyOtherPOJO class.

Vert.x has built-in codecs for certain data types:

- basic types (string, byte array, byte, int, long, double, boolean, short, char), or

- some Vert.x data types (buffers, JSON array, JSON objects), or

- types implementing the `ClusterSerializable` interface, or

- types implementing the `java.io.Serializable` interface.

Important | In clustered mode, `ClusterSerializable` and `java.io.Serializable` objects are rejected by default, for security reasons. You can define which classes are allowed for encoding and decoding by providing functions which inspect the name of the class: `EventBus.clusterSerializableChecker()`, and `EventBus.serializableChecker()`.