Patterns: Implementing Self-Service in an SOA Environment

Chapter 4. Runtime patterns 65

򐂰 Improves reuse.

򐂰 Addresses any technical and information model discrepancies amongst

services.

򐂰 Provides a single configuration point for distributed deployment.

򐂰 Decouples service requesters from providers

򐂰 Provides a common access point for service requesters

򐂰 Provides centralized security for services

The ESB can span across multiple system/application tiers, and may extend

beyond the enterprise boundary.

Note that this Runtime pattern appears to be identical to the SOA profile of the

Runtime pattern for the Directly Integrated Single Channel application pattern.

The use of SOA and an ESB introduces the flexibility to accommodate a wide

range of functionality, including point-to-point, routing, and as we will see later,

decomposition capability.

4.4 Runtime patterns for Decomposition

The Decomposition application pattern expands on the Router application

pattern, providing all the features and functions of that pattern and adding

recomposition/decomposition. This capability allows an incoming request to be

split into multiple requests directed to separate back-end applications. The

results of these requests is recombined into a single response to the user.

The Runtime pattern for the Decomposition application pattern has been broken

down into a generic Runtime pattern and then further refined using an SOA

profile.

4.4.1 Generic Runtime pattern for Decomposition

The Runtime pattern shown in Figure 4-6 on page 66 represents one solution for

the Decomposition application pattern.

66 Patterns: Implementing Self-Service in an SOA Environment

Figure 4-6 Decomposition application pattern::Generic runtime pattern

In the Decomposition application pattern, the decomposition tier serves as an

integration point for delivery channels in the presentation tier, allowing access to

individual back-end applications. In the Generic runtime pattern (Figure 4-6 on

page 66), the functions of the decomposition tier are performed by an integration

server node. The functions of the presentation tier are performed jointly by a

Web server redirector node and the application server node. Placing a Web

server redirector in the DMZ provides an extra layer of security by putting all

application logic behind the firewall. Only a portion of the presentation function is

left in the DMZ.

The Web server redirector serves static HTTP pages, while forwarding dynamic

servlet and JSP requests to the application server. The presentation logic,

therefore, spans both nodes. Together, these two provide the presentation tier,

capable of handling multiple, diverse presentation styles. Using a redirector

allows you to place the bulk of the business logic behind the protection of both

the protocol and domain firewalls.

In addition to presentation logic (for example, JSPs), the application server

contains some business logic. This is primarily in the form of the controlling

servlets required to access the back-end applications. The application server

builds a request based on user input and passes it to the integration server node.

The primary business logic resides in the back-end applications.

Internal Network

Demilitarized Zone

(DMZ)

Outside World

Protocol

Firewall

I

N

T

E

R

N

E

T

Public Key

Infrastructure

User

Web

Server

Redirector

Domain Name

Server

Directory and

Security

Services

Application

Server

Presentation

Decomposition application pattern

Application

Application

Decomposition

Integration

Server

Existing

Applications

and Data

Domain

Firewall

Presentation