Header Mediator

The Header Mediator allows you to manipulate SOAP and HTTP headers.

Info

The Header mediator is a conditionally content aware mediator.

Syntax

<header name=”string” (value=”string|{property}” | expression=”xpath|jsonpath”) [scope=default|transport] [action=set|remove]/>

The optional action attribute specifies whether the mediator should set or remove the header. If no value is specified, the header is set by default.

Configuration

The parameters available to configure the Header mediator are as follows.

Parameter Name Description
Name The name of the header element. You can specify the namespace used in the header element by clicking the Namespaces link next to the text field.
Action Select Set if you want to set the header as a new header. Select Remove if you want to remove the header from the incoming message.
Value/Expression A static value or an XPath/JSONPath expression that will be executed on the message to set the header value.
Inline XML Header

This parameter allows you to directly input any XML syntax related to the Header mediator (specifically for SOAP headers). For example, to achieve the following configuration, you should enter the lastTradeTimestamp element in the Inline XML Header parameter.

<header>  
   <urn:lastTradeTimestamp xmlns:urn=" http://synapse.apache.org/ ">Mon May 13 13:52:17 IST 2013</urn:lastTradeTimestamp>  
</header>
Scope Select Default if you want to manipulate SOAP headers. Select Transport if you want to manipulate HTTP headers.
Namespaces You can click this link to add namespaces if you are providing an expression. The Namespace Editor panel would appear. You can enter any number of namespace prefixes and URL that you have used in the XPath expression in this panel.

Note

The following headers cannot be modified by the header mediator.

  • Content-Length : recalculated automatically based on payload size.
  • Host : controlled by the HTTP transport when connecting to the target endpoint.
  • Transfer-Encoding : controlled by HTTP transport.
  • Connection : controlled by the HTTP transport.
  • Date : automatically generated by the server when sending a response.
  • Server : controlled by the HTTP transport.
  • Content-Type : can be set in Header Mediator, but if a Payload Mediator or MessageType property changes the message type later, it will overwrite it.

Note

When the flow initiated from a proxy service, to set the SOAPAction header when calling to a SOAP endpoint, use the Action header name in the default scope. For example, <header name="Action" scope="default" value="soapActionValue"/>

The following header names in the default scope have a special meaning.

  • Action : Sets the HTTP SOAPAction header.
  • To : Sets the WS-Addressing To header.
  • ReplyTo : Sets WS-Addressing ReplyTo EPR.
  • MessageID : Sets WS-Addressing MessageID.
  • From : Sets WS-Addressing From EPR.
  • FaultTo : Sets WS-Addressing FaultTo EPR.

Examples

This section covers the following scenarios in which the Header mediator can be used.

Using SOAP headers

In the following example, the value for P1 code should be included in the SOAP header of the message sent from the client to the Micro Integrator. To do this, the header mediator is added to the in sequence of the proxy configuration as shown below.

To get a response with Hello World in the SOAP header, the header mediator is also added to the out sequence.

<inSequence>
        <header>
             <p1:Code xmlns:p1="http://www.XYZ.com/XSD">XYZ</p1:Code>
        </header>
        <send>
           <endpoint>
              <address uri="http://localhost:8899/services/SimpleStockQuoteService?wsdl"/>
           </endpoint>
        </send>
     </inSequence>
     <outSequence>
        <header>
           <p2:Header xmlns:p2="http://www.ABC.com/XSD">
              <p2:Hello>World</p2:Hello>
           </p2:Header>
        </header>
        <send/>
</outSequence>

Using HTTP headers

The following example makes the ESB profile add the HTTP header Accept with the value image/jpeg to the HTTP request made to the endpoint.

<inSequence>
    <header name="Accept" value="image/jpeg" scope="transport"/>
    <send>
        <endpoint name="people">
            <address uri="http://localhost:9763/people/eric+cooke" format="get"/>
        </endpoint>
    </send>
</inSequence>
<outSequence>
    <send/>
</outSequence>

If you have enabled wire logs, you will view the following output.

<< GET /people/eric+cooke HTTP/1.1
<< Accept: image/jpeg
<< Host: localhost:9763
<< Connection: Keep-Alive

Handling headers with complex XML

A header can contain XML structured values by embedding XML content within the <header> element as shown below.

<header>
    <m:complexHeader xmlns:m="http://org.synapse.example">
        <property key="k1" value="v1" />
        <property key="k2" value="v2" />
    </m:complexHeader>
</header>

Adding a dynamic SOAP header

The following configuration takes the value of an element named symbol in the message body (the namespace http://services.samples/xsd), and adds it as a SOAP header named header1 .

<header xmlns:m="http://org.synapse.example" xmlns:sym="http://services.samples/xsd" name="m:header1" scope="default" expression="//sym:symbol"/>

Setting the endpoint URL dynamically

In this example, the Header mediator allows the endpoint URL to which the message is sent to be set dynamically. It specifies the default address to which the message is sent dynamically by deriving the To header of the message via an XPath expression. Then the Send mediator sends the message to a Default Endpoint. A Default Endpoint sends the message to the default address of the message (i.e. address specified in the To header). Therefore, in this scenario, selecting the Default Endpoint results in the message being sent to relevant URL calculated via the fn:concat('http://localhost:9764/services/Axis2SampleService_',get-property('epr')) expression.

<header name="To" expression="fn:concat('http://localhost:9764/services/Axis2SampleService_',get-property('epr'))"/>
<send>
<endpoint>
<default/>
</endpoint>
</send>

Setting the header with a value in the JSON body

<header name="header-symbol" expression="json-eval($.symbol)"/>
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