When organizations need to make the data available to users spread pdf

SQL Server 2005 provides native Hypertext Transfer Protocol HTTP support that allows you to create Web services on the database server.. These Web services expose Web methods that the We

When organizations need to make the data available

to users spread across various locations, they

implement Web applications These Web

applications make use of certain services, known as

Web services that provide programming support and help the applications to interact with the database

server To allow communication between the Web

services and the database server, you need to

provide access through additional ports on the

Internet firewall This increases the security threat to the organization

SQL Server 2005 provides native Hypertext

Transfer Protocol (HTTP) support that allows you to create Web services on the database server These

Web services expose Web methods that the Web

applications can access by using the HTTP

endpoints

This chapter introduces you to Web services Next,

it discusses the role of the HTTP endpoints in the

Web service architecture Further, it explains how to implement HTTP

In this chapter, you will learn to:

 Define the Hypertext Transfer Protocol

endpoints

 Implement the Hypertext Transfer Protocol

endpoints for Web services

Objectives

Consider a scenario of a large-scale enterprise that has a number of sales executives The

management has decided to provide Personal Desktop Assistant (PDA) devices to the

sales executives so that they can log the sales details online In addition, the executives

need to connect the PDA device to the database server Providing direct access from a

PDA device to the database server involves a high cost Instead, the management can

implement Web services through which each sales executive can log the sales details

A Web service is a collection of methods or functions where each method provides a

specific functionality When a client sends a request, a Web service accesses data on a

predefined set of business logic from the server and returns the data to the client SQL

Server 2005 provides the native support for Web services through the database engine

using HTTP HTTP is the protocol used for communication over the Internet With this

feature, you can create Web services in the SQL Server Further, you can create the HTTP

endpoints to expose these services to the clients who can directly access these services

over the Internet

The Web services are based on the Service-Oriented Architecture (SOA) Therefore,

before you understand how the Web services are implemented in the SQL Server, it is

essential to know about the SOA

SOA is an extension of distributed computing based on the request/reply design pattern It

follows the n-tier architecture where the business logic of an application is modularized

and presented as services The architecture involves two types of entities, service provider

and service consumer A service provider implements a set of services in the form of

functions In addition, the service provider exposes its functionality through an interface

A service consumer uses the interface to make requests to the service provider to use the

services

Introduction to HTTP Endpoints

Introduction to SOA

The service provider processes the request and sends a reply to the consumer, as shown in the following figure

The SOA

Consider an example of a large business organization that has a number of clients using diverse hardware and software platform, such as a PDA, laptop, Linux, Tablet PC, or a mobile phone In such a scenario, an architecture that enables communication between different types of clients and servers is required SOA allows creating interoperable services that can be accessed from heterogeneous systems Interoperability enables a service provider to host a service on any hardware or software platform that can be different from the platform on the consumer end

In addition, SOA provides the following benefits:

1 Enables better reusability of existing business logic in the enterprise and allows you

to create applications that can be built on the new and existing applications For example, a service provides logic to validate the identity of a customer If you need

to build two different business applications that need to validate identity of a

customer, you can use the same service for that purpose

2 Enables changes to applications while keeping clients or service consumers isolated from the changes In the preceding example of a service that validates the identity of

a customer, if you need to update the logic of this service, you can only update the service You do not need to make any change in the business applications that use the service

A Web service is a set of functions that provide programmable logic used by client applications over the Internet These services are based on the SOA and communicate

through the Simple Object Access Protocol (SOAP) SOAP is an XML-based message

envelop based on HTTP The clients send and receive messages in the XML format and communicate with the service by using HTTP

Introduction to Web Services

For example, a Web service provides the latest stock details of a stock exchange Various

websites that need to display the stock details can use this service to get the latest updates

This service will use SOAP to communicate with the clients

A Web service is implemented in the Internet environment, as shown in the following

figure

Web Services

A Web service encapsulates the implementation of the functions and provides an interface

through which the clients can call these functions This interface is provided in the XML

format in an industry standard called Web Services Definition Language (WSDL) WSDL

is a document that is used by the Web clients to retrieve information about the names of

the methods and their parameters

Each Web service needs to be published by using a protocol called Universal Description,

Discovery and Integration (UDDI) UDDI helps the client applications locate the

published Web services

Web services provide the following benefits:

„ Interoperability: A Web service communicates by using the HTTP protocol, which

is the standard protocol followed by the industry Therefore, a Web service can be

used by any client application that can communicate through HTTP

„ Multilanguage support: A Web service can be created by using any programming

language

Just a minute:

„ Reusability: A Web service created for a particular application can be reused in

other applications as it follows the industry standards for implementation and communication

Web Services in SQL Server

A Web service provides a programming logic to implement a business rule It can also manipulate data in a database server SQL Server 2005 provides the native HTTP support within the database engine that allows database developers to create Web services This allows the database users to interact with the database over the Internet by using a Web service

When you use the native Web services of the SQL Server, you can send SOAP messaging requests to an instance of the SQL Server over HTTP to run the following:

„ Transact-SQL batch statements, with or without parameters

„ Stored procedures and scalar-valued user-defined functions

Which of the following describes the Web services?

To use the native XML Web services of the SQL Server, you need to establish an HTTP

endpoint at the server This endpoint is the gateway through which HTTP-based clients

can send queries to the server An HTTP endpoint listens and receives client requests on

port 80 These requests are listened and routed to the endpoint by the Http.sys listener

process

Identifying the Role of HTTP Endpoints in a Native Web

Service Architecture

Just a minute:

The following figure shows how the HTTP endpoint allows users to communicate with the Web services implemented on the SQL Server

The HTTP Endpoint Architecture

After establishing an HTTP endpoint, you can create stored procedures or user-defined functions that can be made available to endpoint users These procedures and functions are also called as Web methods The Web methods together can be called a Web service The SQL Server instance provides a WSDL generator that helps generate the description

of a Web service in the WSDL format, which is used by the clients to send requests

On which of the following ports does the SQL Server listen for HTTP requests?

As a database developer, you can configure an instance of SQL Server 2005 as a Web

service that can listen natively for HTTP SOAP requests To perform this task, you need

to create HTTP endpoints and define the properties and methods that an endpoint exposes

An HTTP endpoint opens the database to all the trusted users of your data At times, you

might need to restrict the access to the data to selected users only Therefore, it is

important to secure the HTTP endpoints by granting permissions to only selected users to

access an HTTP endpoint

As a database developer, you need to create HTTP endpoints to allow users to access a

Web service implement in the database engine For example, for an organization, you

need to allow the sales executives to add or update order details in a database For this,

you can create a Web service and an HTTP endpoint through which the users will execute

the service

Before implementing an HTTP endpoint, you need to first create the database code that

provides the functionality to the client applications

Creating the Required Database Code

To provide access of data to various users on the net, you need to create stored procedures

or functions which further will be converted into Web method The code allows the users

to perform data manipulations or generate reports that are further accessed from the

Internet

Consider an example, where the database users need to frequently generate reports that

display the aggregated sales data or to retrieve details of customers in a particular region

of an organization You can create stored procedures that generate the desired results

Creating an HTTP Endpoint Object

After creating the database objects, you need to create an HTTP endpoint This object

provides the users with a connecting point through which they can access the

implemented functions

When you create an HTTP endpoint, the SQL Server converts the database objects into

Web methods These Web methods return data that is compatible with the Web standards

These Web methods can be called from any client applications, regardless of the platform

of the client applications, to access data

Implementing the HTTP Endpoints for Web Services

Creating HTTP Endpoints

You can use the CREATE ENDPOINT statement to create an HTTP endpoint The syntax

of the CREATE ENDPOINT statement is:

CREATE ENDPOINT endpoint_name

STATE = { STARTED | STOPPED | DISABLED }

AS HTTP ( AUTHENTICATION =( { BASIC | DIGEST |

[ , SCHEMA = { NONE | STANDARD | DEFAULT } ]

[ , FORMAT = { ALL_RESULTS | ROWSETS_ONLY } ])

} [ , n ] ]

[ BATCHES = { ENABLED | DISABLED } ]

[ , WSDL = { NONE | DEFAULT | 'sp_name' } ]

where,

Endpoint_name is the name of the endpoint that you want to create

STATE = { STARTED | STOPPED | DISABLED } specifies the state of the endpoint when

it is created

AUTHENTICATION = ( { BASIC | DIGEST | NTLM | KERBEROS | INTEGRATED })specifies the authentication method that will be used to verify the clients accessing the endpoint This parameter accepts any of the following values:

„ BASIC: Basic authentication contains the user name and password in an encoded format separated by a colon It can be useful when the endpoint needs to be accessed locally or on the server itself

„ DIGEST: In digest authentication, the user name and password is hashed by using MD5, which is a one-way hashing algorithm The username and password sent by using digest authentication must be mapped to a windows account Digest authentication can be used for crucial data that needs to be accessed when required

„ NTLM: This protocol uses encryption for secure transmission of passwords It provides more security than Basic or Digest authentication

„ KERBEROS: Kerberos authentication is an internet standard authentication While using this mechanism, the SQL server must associate a Service Principal Name with the account accessing the endpoint

„ INTEGRATED: Integrated authentication can use NTLM or Kerberos authentication to authenticate the client Integrated authentication can authenticate the client with the type the client requests

Note

PATH = 'url' specifies the Uniform Resource Locator (URL) path which is a the

location where the endpoint will be stored on the host computer The name of the host computer is specified by the SITE parameter

PORTS= ( { CLEAR | SSL} [ , n ] ) specifies one or more listening port types that are associated with the endpoint This parameter can accept CLEAR or SSL Clear

specifies that the incoming requests should be coming from HTTP where as SSL specifies that the requests should come for secure http(HTTPS)

[ WEBMETHOD [ 'namespace' ] 'method_alias' ] is the method that will be used to accept the requests from the http client Method_alias specifies an alternate name for a Web method that a client can use to access the method

NAME = 'database.schema.name' specifies the name of the stored procedure or defined function that corresponds to the SOAP method specified in WEBMETHOD [ SCHEMA = { NONE | STANDARD | DEFAULT } ] determines whether an inline XSD schema will be returned for the current Web method in the SOAP responses You can use any of the following types with the SCHEMA parameter:

user-„ NONE: The XSD schema is not returned for the SELECT statement results sent through SOAP

„ STANDARD: The XSD schema is returned for the SELECT statement results sent through SOAP

„ DEFAULT: Defaults to the endpoint SCHEMA option setting

If a schema is not specified or if this option is set to DEFAULT, the SCHEMA option

specified for the endpoint determines whether the SCHEMA for the method result is

returned

[ FORMAT = { ALL_RESULTS | ROWSETS_ONLY } ] specifies what will be returned by the Web method The default is ALL_RESULTS You can use any of the following with the FORMAT parameter:

„ ALL_RESULTS: Returns a result set, a row count, error messages, and warnings in the SOAP response

„ ROWSETS_ONLY: Returns only the result sets

BATCHES = { ENABLED | DISABLED } Specifies that whether the endpoint will process the ad hoc requests or not

WSDL = { NONE | DEFAULT | 'sp_name' } indicates whether the WSDL document generation is supported for this endpoint If NONE, no WSDL response is generated or returned for the WSDL queries submitted to the endpoint If DEFAULT, a default WSDL

Note

response is generated and returned for the WSDL queries submitted to the endpoint In exceptional cases, where you are implementing custom WSDL support for the endpoint, you can also specify a stored procedure by name that will return a modified WSDL document

You need to be a member of the sysadmin role to create an endpoint

Consider an example You have created a procedure, getSalesDetails that returns a result set You need to create an HTTP endpoint named sqlEndpoint to provide the

getSalesDetails procedure as a Web method For this, you need to use the following statement in the SQL Server:

CREATE ENDPOINT sqlEndpoint

In the preceding code, getSalesDetails is the name of the procedure that will be converted into a Web method The authentication type used is INTEGRATED and the URL of the endpoint is “/sql”