Oracle® Fusion Middleware
Part 31. Extend filters

A message attribute selector can refer to a field of that message (for example certificate), and you can use . characters to access subfields. For example, the following selector expands to the username field of the object stored in the profile attribute in the message:

${profile.username}

You can also access fields indirectly using square brackets ([ and ]). For example, the following selector is equivalent to the previous example:

${profile[field]}

You can specify literal strings as follows:

${profile["a field name with spaces"]}

For example, the following selector uses the kathy.adams@acme.com key value to look up the User table in the KPS, and returns the value of the age property:

${kps.User["kathy.adams@acme.com"].age}

	Note
	For backwards compatibility with the . spacing characters used in previous versions of the API Gateway, if a selector fails to resolve with the above rules, the flat, dotted name of a message attribute still works. For example, ${content.body} returns the item stored with the content.body key in the message.

The following top-level keys have a special meaning:

Each ${...} selector string is resolved step-by-step, passing an initial context object (for example, Message). The top-level key is offered to the context object, and if it resolves the field (for example, the message contains the named attribute), the resolved object is indexed with the next level of key. At each step, the following rules apply:

	Note
	Method calls are currently only supported using Java reflection. There are currently no supported functions as specified by the Unified Expression Language (EL) standard. For more details on JUEL, see http://juel.sourceforge.net/.

The following message attribute selector returns the HTTP User-Agent header:

${http.headers["User-Agent"]}

For example, this might expand to the following value:

Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/535.7 (KHTML, like Gecko) Chrome/16.0.912.77 
Safari/535.7

In a default configuration, the following environment variable selector returns port 8091:

${env.PORT.MANAGEMENT + 1}

The following selector looks up a KPS table with an alias of User:

${kps.User[http.querystring.id].firstName}

This selector retrieves the object whose key value is specified by the id query parameter in the incoming HTTP request, and returns the value of the firstName property in that object.

The following selector explicity provides the key value, and returns the value of the age property:

${kps.User["kathy.adams@acme.com"].age}

In this example, the ASCII " character is used to delimit the key string.

The following selector looks up a KPS table with a composite secondary key of firstName,lastName:

${kps.User[http.querystring.firstName][http.querystring.lastName].email}

In this example, the key values are received as query parameters in the incoming HTTP request. The selector returns the value of the email property from the resulting object.

The following message attribute selector returns the CGI argument from an HTTP URL (for example, returns bar for http://localhost/request.cgi?foo=bar):

${http.client.getCgiArgument("foo")}

This returns the name of the top-level element in an XML document:

${content.body.getDocument().getDocumentElement().getNodeName()}

This returns true if the HTTP response code lies between 200 and 299:

${http.response.status / 200 == 2}