PROTOCOL CLIENTS

<?xml version="1.0" encoding="UTF-8"?>

<definitions name="Backend" xmlns:typens="urn:ActionWebService" . . .

<types>

<xsd:schema xmlns="http://www.w3.org/2001/XMLSchema" . . .

<xsd:complexType name="Product"> <xsd:all>

<xsd:element name="id" type="xsd:int"/> <xsd:element name="title" type="xsd:string"/>

<xsd:element name="description" type="xsd:string"/> <xsd:element name="image_url" type="xsd:string"/>

<xsd:element name="price" type="xsd:double"/>

<xsd:element name="date_available" type="xsd:dateTime"/>

</xsd:all>

</xsd:complexType>

<xsd:complexType name="IntegerArray"> <xsd:complexContent>

<xsd:restriction base="soapenc:Array">

<xsd:attribute wsdl:arrayType="xsd:int[]" ref="soapenc:arrayType"/> </xsd:restriction>

</xsd:complexContent> </xsd:complexType>

</xsd:schema>

</types>

<message name="FindAllProducts">

</message>

<message name="FindAllProductsResponse">

<part name="return" type="typens:IntegerArray"/>

</message>

<message name="FindProductById"> <part name="param0" type="xsd:int"/>

</message>

. . .

Figure 20.4: WSDL Generated by AWS

Having two different URLs for these different cases may seem arbitrary, but there is a reason. For delegated and layered dispatching, the information telling us which service object the invocation should be routed to is embedded in the request. For delegated dispatching we rely on the controller action name to determine which service it should go to.

Note that these URLs are used as both the SOAP and XML-RPC message endpoints; AWS is able to determine the type of message from the request.

20.7 Protocol Clients

Action Web Service includes some client classes for accessing remote web services. These classes understand Action Web Service API definitions, so if we have the API definition of a remote service, we can access that service

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with type conversion to and from the correct types occurring automatically for us.

However, these are not general-purpose clients. If our client application is not tightly coupled to the server, it may make more sense to use Ruby’s native SOAP and XML-RPC clients.

If we want to access a remote web service API from inside a controller with the AWS clients, use the web_client_api( ) helper function.

class MyController < ApplicationController

web_client_api :product, :soap,

"http://my.app.com/backend/api"

def list

@products = product.find_all_products.map do |id| product.find_product_by_id(id)

end end

end

The web_client_api declaration creates a protected method named product( ) in the controller. This uses the ProductApi class we created in the first example. Calling the product( ) method returns a client object with all the methods of ProductApi available for execution.

We can also invoke the web service API directly by creating an instance of the client for the relevant protocol (either ActionWebService::Client::Soap or ActionWebService::Client::XmlRpc). We’ll then be able to invoke API methods on this instance.

shop = ActionWebService::Client::Soap.new(ProductApi,

"http://my.app.com/backend/api") product = shop.find_product_by_id(5)