Patterns: Broker Interactions for Intra- and Inter-enterprise

154 Broker Interactions for Intra- and Inter-enterprise

8.3 Applying patterns

The Retail system needs to get delivery dates based on a part or system number

from the appropriate Wholesale supplier. Each Wholesale supplier has its own

unique implementation that returns the delivery date to requesters but has

basically the same input and output formats for incoming requests and outgoing

responses. Each Wholesale system does not necessarily support the same

protocol for transmission of the requests and responses.

From this, ITSO Electronics determined the following requirements:

򐂰 Each Wholesale department must expose its services as Web services.

The actual implementation on the Wholesale systems must be transparent to

the Retail system. The request for a delivery date will be done as a Web

service invocation, relieving the Retail system from having to know how the

request is fulfilled.

򐂰 The design must be able to support multiple protocols and perform protocol

transformation.

For the same Web service, Wholesale1 offers a SOAP/HTTP implementation,

while Wholesale2 offers a SOAP/JMS implementation. Although the Retail

system will initially use SOAP/HTTP as an interface, future requirements will

include the need to access the services using SOAP/JMS.

8.3.1 Application patterns

A Router node provides the multi-protocol transformation and intelligent request

routing required for the solution, therefore ITSO Electronics decided to use the

Application Integration Router pattern to design the solution.

To phase in the solution, they decided to implement it in stages.

Stage 1: Basic integration

In the first stage, the Retail system requests either the service of the Wholesale1

or Wholesale2 department. This assumes that the Retail system knows which

Wholesale department is the supplier for a particular part number. This solution

requires simple router functions, which will be supplied by Web Services

Gateway.

The request is directed to the Router node, which invokes the Web service from

the requested Wholesale department. The Router presents a unified interface for

the Retail system and transforms the message to the appropriate transport

protocol for the target. It also performs logging of the event.

Chapter 8. Router solutions using Web Services Gateway 155

The solution implemented in this stage by ITSO Electronics is shown in

Figure 8-3.

Figure 8-3 Basic Router implementation

Stage 2: Enhanced integration

In the second stage, ITSO Electronics will enhance the solution so the Retail

system no longer needs to know which Wholesale department supplies the part.

The Retail system can simply send the request to the Router, which will

determine the appropriate Wholesale system and invoke the Web service. This

places a requirement on the Router that it provide content-based routing.

The solution implemented in this stage by ITSO Electronics is shown in

Figure 8-4.

Figure 8-4 Enhanced Router implementation

Stage 3: Extended enterprise

In the third stage, ITSO Electronics will enhance the solution so that external

Retail systems can request delivery dates from the Wholesale departments. The

implementation does not change, but the Web Services Gateway is opened up to

the externals and protected with a firewall; and additional security concerns are

addressed.

SOAP/

HTTP

Router Rules

SOAP/

JMS

ITSO Electronics

Wholesale

ITSO Electronics

Wholesale

ITSO

Electronics

Retail

SOAP/

HTTP

SOAP/

HTTP

SOAP/

JMS

ITSO Electronics

Wholesale

ITSO Electronics

Wholesale

ITSO

Electronics

Retail

SOAP/

HTTP

Router Rules

156 Broker Interactions for Intra- and Inter-enterprise

The solution implemented in this stage by ITSO Electronics is shown in

Figure 8-5.

Figure 8-5 Extended enterprise implementation

Similarly, the solution could provide the Retail systems in ITSO Electronics could

access external Wholesale companies.

Figure 8-6 Extended enterprise implementation

In either case, the Router node can be placed on the secure internal network

behind the DMZ. The advantage of this configuration is that the gateway can

provide access to services using protocols that are not as firewall-friendly as

HTTP. For example, the Router node can enable Web service clients to access

EJB, JMS, and JavaBean applications.

The Router node could also be located in the DMZ. All the firewalls in our

example are configured for network address translation, so SOAP over HTTP

can be used to pass through the firewalls. This may not work if the gateway is

using RMI to access an EJB on the secure network, for example.

External

Retail

SOAP

/HTTP

SOAP/

JMS

Firewall

Firewall

SOAP/

HTTP

Firewall

Firewall

DMZ

ITSO Electronics

Wholesale

ITSO Electronics

Wholesale

Router Rules

SOAP/

HTTP

SOAP/

HTTP

Firewall

Firewall

Firewall

Firewall

DMZ

ITSO

Electronics

Retail

SOAP/

JMS

External

Wholesale

External

Wholesale

Router Rules