HTTP Header Setter mediation primitive

Use the HTTP Header Setter primitive to create, modify, copy or delete HTTP message headers.

Introduction

You can use the HTTP Header Setter mediation primitive to provide a mechanism for managing HTTP headers in the message. You can change, copy, add, or delete HTTP headers by setting the mediation primitive properties.

If you want multiple header changes you can set multiple actions. Multiple actions are acted on sequentially, in the order in which they are specified; this means that header changes can build on each other.

You can create new HTTP headers by specifying header field values. You can search for HTTP headers that already exist in the SMO by specifying the header name to match on. If a matching header is found, it can then be deleted from the message, copied to another location in the SMO, or have the value set. If a matching header is not found, a new header can be created using a specified header field value.

The HTTP Header Setter mediation primitive has one input terminal (in), one output terminal (out) and a fail terminal (fail). The in terminal is wired to accept a message and the other terminals are wired to propagate a message. If the mediation is successful, the out terminal propagates the modified message. If an exception occurs during the transformation, the fail terminal propagates the original message, together with any exception information contained in the failInfo element.

The HTTP Header Setter mediation primitive uses the given header name to determine where to look in the SMO. There are three different types of HTTP Header, distinguished by name and their location in the SMO.

HTTP Control Headers, which have their own schema in the SMO, located at /headers/HTTPHeader/control. The names of these headers are relative XPaths.
HTTP Spec Headers, which are listed in the SMO at /headers/HTTPHeader/header. The names of these headers are from the HTTP 1.1 spec
Any other headers are User Headers and are listed at /headers/properties.

Usage

You can use the HTTP Header Setter mediation primitive to ensure that when a HTTP message is sent to another system, via the HTTP binding, the headers that are sent with the message are correctly set.

Because the operations you define occur sequentially, a later operation can depend on an earlier operation. For example, you could create a new header, copy it to elsewhere in the SMO and then delete it from the list of headers it was initially appended to.

You can also use the HTTP Header Setter mediation primitive to help to filter messages, using the Message Filter mediation primitive. You might want to find a particular header and make it available to be used in the filtering.