Introduction
Apache Synapse supports standard XPath functions and variables through its underlying XPath engine. Apart from standard XPath functions, there are several custom XPath functions and variables defined by Synapse to retrieve various message context properties.
Custom Functions
get-property function
Get property function retrieves a property from the message context at the given scope. If the scope is not specified, property is retrieved from the default synapse scope.
Syntax:
Default scope
Message context properties residing in Synapse scope can be retrieved from the default scope. These are the properties directly set on the Synapse MessageContext instance. Apart from user defined properties, following special properties can also be retrieved from the default scope.
| Name | Return Value |
| To | Incoming URL as a String or empty string if a To address is not defined. |
| From | From address as a String or empty string if a From address is not defined |
| Action | SOAP Action header value as a String or empty string if a Action is not defined |
| FaultTo | SOAP FautTo header value as a String or empty string if a FaultTo address is not defined |
| ReplyTo | ReplyTo header value as a String or empty string if a ReplyTo address is not defined |
| MessageID | A unique identifier (UUID) for the message as a String . This id is guaranteed to be unique. |
| FAULT | TRUE if the message has a fault or empty string if message doesn't have a fault |
| MESSAGE_FORMAT | Returns pox, get, soap11, soap12 depending on the message. If a message type is unknown this returns soap12 |
| OperationName | Operation name corresponding to the message. |
Axis2 scope
Message context properties residing in axis2 scope can be retrieved from the axis2 scope. These are the properties set on the underlying Axis2 MessageContext object.
Transport scope
Message context properties residing in transport scope can be retrieved from the transport scope. These are the transport headers set on the MessageContext.
Registry scope
Properties residing in registry can be retrieved from the registry scope.
System scope
Java System properties can be retrieved from the system scope.
base64Encode function
Returns the base64 encoded value of the argument.
Syntax:
base64Decode function
Returns the base64 decoded value of the argument.
Syntax:
Variables
There are several XPath variables supported by Synapse. These are used for accessing various properties from the message context
- $axis2
- $trp
- $ctx
- $url
- $body
- $header
These XPath variables get the properties at various scopes.
$ctx
Variable prefix for accessing the MessageContext properties in default scope.
i.e To get the property named 'foo' at the default scope use the following XPath expression
$axis2
Variable prefix for accessing the axis2 MessageContext properties
i.e. To get the property named 'messageType' use the following XPath expression
$trp
Variable prefix for accessing transport headers of the message
i.e. To get the transport header named Content-Type use the following XPath expression
$url
Variable prefix for accessing URL parameters of the message
i.e. To get the URL parameter named 'bar' use the following XPth expression
$body
Get the message body
$header
Get the soap header