Introducing Windows Azure- P29 pot

■ ■ ■ 113 Windows Azure Application Integration Using WCF Whenever a new technology is introduced to the computing world, it raises a lot of questions for an enterprise or organizatio

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113

Windows Azure Application

Integration Using WCF

Whenever a new technology is introduced to the computing world, it raises a lot of questions for an

enterprise or organization regarding integration How do you integrate an application built on new

technology into the existing system infrastructure? What are appropriate tools to select for integration? How do you select the right candidate subsystem to migrate, refactor, or re-engineer? Although Windows Azure provides a revolutionary new platform, it is almost impossible for any organization to migrate the entire existing on-premises system and infrastructure into the cloud platform Therefore, integration

strategies are extremely important Even subsystems, which are built with Windows Azure technology, still need to be integrated together Microsoft has already provided cloud-computing-based services,

such as NET Services, SQL Azure, and Live Services These services provide organizations with rich

functionality and a broad range of building blocks for integration

Windows Azure offers amazing, innovative, and attractive features One of these features is the

ability to host an application in the cloud Not only cloud-based applications, but also the on-premises applications can leverage cloud services and applications As I mentioned, to run an application from

the cloud is far from the whole story There is always an integration issue associated with the system

architecture design It should not be too difficult to understand why integration plays the essential role All applications, services, and infrastructures involved in a computing system need to be coordinated in data exchange, resource sharing, status persisting, logic synchronizing, and so on All these tasks should

be done via integration

No matter what integration strategy an organization plans to use, an essential feature of an

integration platform is that it must support cross-platform communication Microsoft BizTalk server

and WCF (Windows Communication Foundation, part of NET 3.0 or later versions of the NET platform) should meet these criteria In principle, Microsoft BizTalk server is designed to support any existing

communication protocol in the computing world through built-in, third-party, or custom adapters The great advantages we can take from Microsoft BizTalk server are its power to integrate and call any

existing NET components, to extend a solution with custom pipelines, data mapping functions, and

dynamic data transforming and mapping And it has sophisticated workflow control, business rules

integration, and error handling via Windows BizTalk orchestrations In contrast, the advantage we can get from WCF is that it is a web-services-based platform WCF is built in to NET 3.0 and later versions

and can be deployed and hosted from Windows Azure The scope of this book is limited to covering the topic of integrating Windows Azure applications with each other or with other ncloud-based

on-premises applications using Windows WCF

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Using WCF

WCF unifies all the communication models supported by web services, including message queues, NET Remoting and distributed transactions into a general service-oriented architecture (SOA), and it also supports SOAP (with an optimized SOAP binary format) WCF also supports both JSON and REST data formats You can flexibly consume data from Windows Azure using Ajax or NET by simply providing URLs of the target resources When a method is invoked against specific URLs, parameters from the URLs are automatically extracted and passed into the target method

These features as described make WCF a great integration tool not only for on-premises

applications but also for Windows Azure cloud applications, in addition to Windows BizTalk server WCF services can be hosted from Windows API applications or from IIS It would make WCF more attractive from the perspective of integration if WCF services could be hosted from Windows Azure

Microsoft NET Services, originally called BizTalk Services, was designed as a set of highly scalable developer-oriented services hosted in Microsoft data centers as part of the Windows Azure platform These services are common building blocks or infrastructure services for cloud-based applications As one of the core services offered by NET Services, NET Workflow Services allows you to define highly scalable cloud-based workflows using Workflow Foundation (WF) In addition, the NET Workflow Service also provides management tools and web-service-based APIs for NET Workflow Services type and instance management Moving forward,.NET Workflow Services tightly collaborates with WCF In this chapter, we are going to explore the fundamental steps of using WCF and WF as a cloud-based application integration platform

Host WCF Service from Azure

In this exercise, we are going to build an example to host a WCF service from Windows Azure Following are the steps we need to perform to reach this goal

1 From Visual Studio, create a new cloud service web role service project called

HostWCFService as shown in Figure 4-1

Figure 4-1 Create a cloud web role service, HostWCFService, from Visual Studio

2 Create a DLL library project called AzureForDotNetDeveloperWCFServiceLibrary In

this project we define a WCF service contract interface, IUserRegisterService, and

a data contract class, User, as Listing 4-1 shows The service contract interface, IUserRegisterService, has two operation contracts defined AddUser() (taking an instance of User as a parameter) is used to provide a service to add a user when a user registers to a cloud application GetUserList() is used to retrieve the collection of users who have registered to a cloud application

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Listing 4-1 WCF Service Contract IUserRegisterService and Data Contract User Definition

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Runtime.Serialization;

using System.ServiceModel;

namespace AzureForDotNetDeveloperWCFServiceLibrary

{

[ServiceContract]

public interface IUserRegisterService

{

[OperationContract]

void AddUser(User user);

[OperationContract]

List<User> GetUserList();

}

[DataContract]

public class User

{

[DataMember]

public string FirstName;

[DataMember]

public string LastName;

[DataMember]

public DateTime TimeRegistered;

[DataMember]

public string Password;

}

}

3 From the HostWCFService WebRole project in the Solution Explorer panel,

right-click on the project node and select Add ➤ New Item to bring up the Add New

Item dialog box Select WCF Service from the dialog window and name it

UserRegisterService.svc as Figure 4-2 shows Add the reference to

AzureForDotNetDeveloperWCFServiceLibrary we have just created There are

three changes we need to make after the service component has been inserted

into the project:

• Open UserRegisterService.svc from Visual Studio by double-clicking on

that file node and correct the string value for Service The string in quotation marks should be the fully qualified class name with namespace:

AzureForDotNetDeveloperWCFServiceLibrary.UserRegisterService

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• Delete UserRegisterService.svc.cs from the project because we have already defined the services contracts from

AzureForDotNetDeveloperWCFServiceLibrary

• Remove the following section from UserRegisterService.svc by double-clicking on that file node from the Solution Explorer panel of Visual Studio The results are shown in Listing 4-2:

<Code behind="HostWCFService WebRole.UserRegisterService.svc.cs"

Figure 4-2 Insert a WCF service item into the HostWCFService WebRole project

Listing 4-2 Modify the File UserRegisterService.svc to Use the Correct Namespace and Remove the Code-behind Section

<%@ ServiceHost Language="C#" Debug="true"

Service="AzureForDotNetDeveloperWCFServiceLibrary.UserRegisterService" %>

4 From Visual Studio, select Tools ➤ WCF Configuration Editor and open the

Web.config file of the HostWCFService project as shown in Figure 4-3 Use this tool to configure the WCF service endpoint and metadata endpoint The results for Web.config are shown in Listing 4-3 The Web.config file can be edited by using any XML editor instead of using WCF Configuration Editor

However I recommend that you edit the WCF configuration file with the configuration editor This is tedious work, and it is very easy to make mistakes

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Figure 4-3 Launch WCF Configuration Editor from Visual Studio

Listing 4-3 Configuration for WCF Service UserRegisterService.svc

<?xml version="1.0"?>

<configuration>

<appSettings>

<add key="AccountName" value="devstoreaccount1"/>

<add key="AccountSharedKey" value="<KEY>"/>

<add key="BlobStorageEndpoint" value="http://127.0.0.1:10000"/>

<add key="QueueStorageEndpoint" value="http://127.0.0.1:10001"/>

<add key="TableStorageEndpoint" value="http://127.0.0.1:10002/"/>

</appSettings>

<connectionStrings/>

<system.webServer>

<validation validateIntegratedModeConfiguration="false"/>

<modules>

<remove name="ScriptModule" />

<add name="ScriptModule" preCondition="managedHandler"

type="System.Web.Handlers.ScriptModule, System.Web.Extensions,

Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>

</modules>

<handlers>