XPath Extension Functions

In addition to standard XPath functions, the ESB supports the following custom functions for working with XPath expressions:

get-property() function

The get-property() function allows any XPath expression used in a configuration to look up information from the current message context. Using the Property mediator, you can retrieve properties from the message context and header.

The syntax of the function takes the following format.

• get-property(String propertyName)
• get-property(String scope, String propertyName)

The function accepts scope as an optional parameter. It retrieves a message property at the given scope, which can be one of the following.

If you provide only the property name without the scope, the default synapse scope will be used.

<inSequence>
<log level="custom">
<property name="WHERE" value="before doing stuff"/>
</log>
<enrich>
<source type="body" clone="true"/>
<target type="property" property="ENRICH_PROPERTY"/>
</enrich>
<property name="PROPERTY_PROPERTY"
expression="$body/child::node()"
scope="default"/>
<log level="custom">
<property name="WHERE" value="before doing stuff"/>
<property name="ENRICH_PROPERTY" expression="get-property('ENRICH_PROPERTY')"/>
<property name="PROPERTY_PROPERTY" expression="get-property('PROPERTY_PROPERTY')"/>
</log>
<enrich>
<source type="property" clone="true" property="ENRICH_PROPERTY"/>
<target type="body" action="sibling"/>
</enrich>
<log level="full"/>
</inSequence>

Synapse scope

When the scope of a property mediator is synapse, its value is available throughout both the in sequence and the out sequence. In addition to the user-defined properties, you can retrieve the following special properties from the synapse scope.

To access a property with the synapses cope inside the mediate() method of a mediator, you can include the following configuration in a custom mediator created using the Class mediator:

public boolean mediate(org.apache.synapse.MessageContext mc) {  
// Available in both in-sequence and out-sequenc  
String propValue = (String) mc.getProperty("PropName");  
System.out.println("SCOPE_SYNAPSE : " + propValue);  
return true;  
}

axis2 scope

When the scope of a property mediator is axis2, its value is available only throughout the sequence for which the property is defined (e.g., if you add the property to an in sequence, its value will be available only throughout the in sequence). You can retrieve message context properties within the axis2 scope using the following syntax.

Syntax:
get-property('axis2', String propertyName)

To access a property with the axis2  scope inside the mediate() method of a mediator, you can include the following configuration in a custom mediator created using the Class mediator:

public boolean mediate(org.apache.synapse.MessageContext mc) {  
org.apache.axis2.context.MessageContext axis2MsgContext;  
axis2MsgContext = ((Axis2MessageContext) mc).getAxis2MessageContext();  
  
// Available only in the sequence the property is defined.  
String propValue = (String) axis2MsgContext.getProperty("PropName");  
System.out.println("SCOPE_AXIS2 : " + propValue);  
return true;  
} 

axis2-client

This is similar to the synapse  scope. The difference is that it can be accessed inside the  mediate()  method of a mediator by including one of the following configurations in a custom mediator, created using the Class mediator :

public boolean mediate(org.apache.synapse.MessageContext mc) {  
org.apache.axis2.context.MessageContext axis2MsgContext;  
axis2MsgContext = ((Axis2MessageContext) mc).getAxis2MessageContext();  
String propValue = (String) axis2MsgContext.getProperty("PropName");  
System.out.println("SCOPE_AXIS2_CLIENT - 1 : " + propValue); 

or

propValue = (String) axis2MsgContext.getOptions().getProperty("PropName");  
System.out.println("SCOPE_AXIS2_CLIENT - 2: " + propValue);  
return true;  
}  

transport scope

When the scope of a property mediator is transport, it will be added to the transport header of the outgoing message from the ESB. You can retrieve message context properties within the transport scope using the following syntax.

Syntax:
get-property('transport', String propertyName)

registry scope

You can retrieve properties within the registry using the following syntax.

Syntax:
get-property('registry', String registryPath@propertyName)
get-property('registry', String registryPath)

system scope

You can retrieve Java System properties using the following syntax.

Syntax:
get-property('system', String propertyName)

operation scope

You can retrieve a property in the operation context level from the operation scope. The properties within iterated/cloned message with the operation scope are preserved in the in sequence even if you have configured your API resources to be sent through the fault sequence when faults exist. A given property with the operation scope only exists in a single request and can be accessed by a single resource. The properties in this scope are passed to the error handler when the FORCE_ERROR_ON_SOAP_FAULT property is set to true. See FORCE_ERROR_ON_SOAP_FAULT section in Generic Properties for more information.

Syntax:
get-property('operation', String propertyName) 

url-encode() function

The url-encode function returns the URL-encoded value of the specified string.

Syntax:

• url-encode(string value)
• url-encode(string value, string charset)

Next, see Synapse XPath Variables.