08_Expressions

Bloodhound – Expressions

In Bloodhound actors configuration, you may find fields allowing dynamic expressions. These expressions get evaluated to generate a dynamic value.

SpEL – Spring Expression Language

The language used by Bloodhound is the Spring Expression Language.

Uses in Bloodhound

All of expressions will make use of the current message being processed. The message is accessible using the #msg keyword.

Here’s a breakdown of many internal members, accessed using SpEL.

#msg: the current message;

#msg.request(): the request object;

#msg.request().getHeader('key'): returns a certain request header;

#msg.request().payload(): the request payload, in the form of an array of bytes;

#msg.request().callId(): the call id, as defined by the EndpointIdentifierActor

#msg.response(): when evaluating a message after the upstream phase, this expression will access the response object;

#msg.response().getHeader('key'): returns a certain response header;

#msg.response().payload(): the response payload, in the form of an array of bytes;

#msg.meta(): the metadata map;

#msg.meta().getOrElse('key','defaultValue'): returns the value of the metadata identified by the key. ‘defaultValue’ in case the metadata does not exist