Category: webservices

Web Services – Architecture ”; Previous Next There are two ways to view the web service architecture − The first is to examine the individual roles of each web service actor. The second is to examine the emerging web service protocol stack. Web Service Roles There are three major roles within the web service architecture − Service Provider This is the provider of the web service. The service provider implements the service and makes it available on the Internet. Service Requestor This is any consumer of the web service. The requestor utilizes an existing web service by opening a network connection and sending an XML request. Service Registry This is a logically centralized directory of services. The registry provides a central place where developers can publish new services or find existing ones. It therefore serves as a centralized clearing house for companies and their services. Web Service Protocol Stack A second option for viewing the web service architecture is to examine the emerging web service protocol stack. The stack is still evolving, but currently has four main layers. Service Transport This layer is responsible for transporting messages between applications. Currently, this layer includes Hyper Text Transport Protocol (HTTP), Simple Mail Transfer Protocol (SMTP), File Transfer Protocol (FTP), and newer protocols such as Blocks Extensible Exchange Protocol (BEEP). XML Messaging This layer is responsible for encoding messages in a common XML format so that messages can be understood at either end. Currently, this layer includes XML-RPC and SOAP. Service Description This layer is responsible for describing the public interface to a specific web service. Currently, service description is handled via the Web Service Description Language (WSDL). Service Discovery This layer is responsible for centralizing services into a common registry and providing easy publish/find functionality. Currently, service discovery is handled via Universal Description, Discovery, and Integration (UDDI). As web services evolve, additional layers may be added and additional technologies may be added to each layer. The next chapter explains the components of web services. Few Words about Service Transport The bottom of the web service protocol stack is service transport. This layer is responsible for actually transporting XML messages between two computers. Hyper Text Transfer Protocol (HTTP) Currently, HTTP is the most popular option for service transport. HTTP is simple, stable, and widely deployed. Furthermore, most firewalls allow HTTP traffic. This allows XMLRPC or SOAP messages to masquerade as HTTP messages. This is good if you want to integrate remote applications, but it does raise a number of security concerns.ise a number of security concerns. Blocks Extensible Exchange Protocol (BEEP) This is a promising alternative to HTTP. BEEP is a new Internet Engineering Task Force (IETF) framework for building new protocols. BEEP is layered directly on TCP and includes a number of built-in features, including an initial handshake protocol, authentication, security, and error handling. Using BEEP, one can create new protocols for a variety of applications, including instant messaging, file transfer, content syndication, and network management. SOAP is not tied to any specific transport protocol. In fact, you can use SOAP via HTTP, SMTP, or FTP. One promising idea is therefore to use SOAP over BEEP. Print Page Previous Next Advertisements ”;

Web Services Questions and Answers ”; Previous Next Web Services Questions and Answers has been designed with a special intention of helping students and professionals preparing for various Certification Exams and Job Interviews. This section provides a useful collection of sample Interview Questions and Multiple Choice Questions (MCQs) and their answers with appropriate explanations. SN Question/Answers Type 1 Web Services Interview Questions This section provides a huge collection of Web Services Interview Questions with their answers hidden in a box to challenge you to have a go at them before discovering the correct answer. 2 Web Services Online Quiz This section provides a great collection of Web Services Multiple Choice Questions (MCQs) on a single page along with their correct answers and explanation. If you select the right option, it turns green; else red. 3 Web Services Online Test If you are preparing to appear for a Java and Web Services Framework related certification exam, then this section is a must for you. This section simulates a real online test along with a given timer which challenges you to complete the test within a given time-frame. Finally you can check your overall test score and how you fared among millions of other candidates who attended this online test. 4 Web Services Mock Test This section provides various mock tests that you can download at your local machine and solve offline. Every mock test is supplied with a mock test key to let you verify the final score and grade yourself. Print Page Previous Next Advertisements ”;

Web Services – Examples ”; Previous Next Based on the web service architecture, we create the following two components as a part of web services implementation − Service Provider or Publisher This is the provider of the web service. The service provider implements the service and makes it available on the Internet or intranet. We will write and publish a simple web service using .NET SDK. Service Requestor or Consumer This is any consumer of the web service. The requestor utilizes an existing web service by opening a network connection and sending an XML request. We will also write two web service requestors: one web-based consumer (ASP.NET application) and another Windows application-based consumer. Given below is our first web service example which works as a service provider and exposes two methods (add and SayHello) as the web services to be used by applications. This is a standard template for a web service. .NET web services use the .asmx extension. Note that a method exposed as a web service has the WebMethod attribute. Save this file as FirstService.asmx in the IIS virtual directory (as explained in configuring IIS; for example, c:MyWebSerces). FirstService.asmx <%@ WebService language = “C#” class = “FirstService” %> using System; using System.Web.Services; using System.Xml.Serialization; [WebService(Namespace = “http://localhost/MyWebServices/”)] public class FirstService : WebService{ [WebMethod] public int Add(int a, int b) { return a + b; } [WebMethod] public String SayHello() { return “Hello World”; } } To test a web service, it must be published. A web service can be published either on an intranet or the Internet. We will publish this web service on IIS running on a local machine. Let us start with configuring the IIS. Open Start → Settings → Control Panel → Administrative tools → Internet Services Manager. Expand and right-click on the default web site; select New rarr; Virtual Directory. The Virtual Directory Creation Wizard opens. Click Next. The “Virtual Directory Alias” screen opens. Type the virtual directory name. For example, MyWebServices. Click Next. The “Web Site Content Directory” screen opens. Enter the directory path name for the virtual directory. For example, c:MyWebServices. Click Next. The “Access Permission” screen opens. Change the settings as per your requirements. Let us keep the default settings for this exercise. Click the Next button. It completes the IIS configuration. Click Finish to complete the configuration. To test whether the IIS has been configured properly, copy an HTML file (For example, x.html) in the virtual directory (C:MyWebServices) created above. Now, open Internet Explorer and type http://localhost/MyWebServices/x.html. It should open the x.html file. Note − If it does not work, try replacing the localhost with the IP address of your machine. If it still does not work, check whether IIS is running; you may need to reconfigure the IIS and the Virtual Directory. To test this web service, copy FirstService.asmx in the IIS virtual directory created above (C:MyWebServices). Open the web service in Internet Explorer (http://localhost/MyWebServices/FirstService.asmx). It should open your web service page. The page should have links to two methods exposed as web services by our application. Congratulations! You have written your first web service! Testing the Web Service As we have just seen, writing web services is easy in the .NET Framework. Writing web service consumers is also easy in the .NET framework; however, it is a bit more involved. As said earlier, we will write two types of service consumers, one web-based and another Windows application-based consumer. Let us write our first web service consumer. Web-Based Service Consumer Write a web-based consumer as given below. Call it WebApp.aspx. Note that it is an ASP.NET application. Save this in the virtual directory of the web service (c:MyWebServicesWebApp.axpx). This application has two text fields that are used to get numbers from the user to be added. It has one button, Execute, that when clicked gets the Add and SayHello web services. WebApp.aspx <%@ Page Language = “C#” %> <script runat = “server”> void runSrvice_Click(Object sender, EventArgs e) { FirstService mySvc = new FirstService(); Label1.Text = mySvc.SayHello(); Label2.Text = mySvc.Add(Int32.Parse(txtNum1.Text), Int32.Parse(txtNum2.Text)).ToString(); } </script> <html> <head> </head> <body> <form runat = “server”> <p> <em>First Number to Add </em>: <asp:TextBox id = “txtNum1” runat = “server” Width = “43px”>4< /asp:TextBox> </p> <p> <em>Second Number To Add </em>: <asp:TextBox id = “txtNum2” runat = “server” Width = “44px”>5</asp:TextBox> </p> <p> <strong><u>Web Service Result -</u></strong> </p> <p> <em>Hello world Service</em> : <asp:Label id = “Label1” runat = “server” Font-Underline = “True”>Label< /asp:Label> </p> <p> <em>Add Service</em> : & <asp:Label id = “Label2” runat = “server” Font-Underline = “True”>Label</asp:Label> </p> <p align = “left”> <asp:Button id = “runSrvice” onclick = “runSrvice_Click” runat = “server” Text = “Execute”></asp:Button> </p> </form> </body> </html> After the consumer is created, we need to create a proxy for the web service to be consumed. This work is done automatically by Visual Studio .NET for us when referencing a web service that has been added. Here are the steps to be followed − Create a proxy for the Web Service to be consumed. The proxy is created using the WSDL utility supplied with the .NET SDK. This utility extracts information from the Web Service and creates a proxy. The proxy is valid only for a particular Web Service. If you need to consume other Web Services, you need to create a proxy for this service as well. Visual Studio .NET creates a proxy automatically for you when the Web Service reference is added. Create a proxy for the Web Service using the WSDL utility supplied with the .NET SDK. It will create FirstSevice.cs file in the current directory. We need to compile it to create FirstService.dll (proxy) for the Web Service. c:> WSDL http://localhost/MyWebServices/FirstService.asmx?WSDL c:> csc /t:library FirstService.cs Put the compiled proxy in the bin directory of the virtual directory of the Web Service (c:MyWebServicesbin). Internet Information Services (IIS) looks for the proxy in this directory. Create the service consumer, in the same way we already did. Note that an object of the Web Service proxy is

Web Services – Useful Resources ”; Previous Next The following resources contain additional information on Web Services. Please use them to get more in-depth knowledge on this topic. Java Web Services Course: Restful API Best Seller 72 Lectures 10 hours Chaand Sheikh More Detail Develop RESTful Java Web Services using JAX-RS and Jersey 28 Lectures 2 hours Vinod Kumar Kayartaya More Detail AWS Application Integration Services Course 15 Lectures 1 hours Harshit Srivastava More Detail Print Page Previous Next Advertisements ”;

Web Services – Characteristics ”; Previous Next Web services have the following special behavioral characteristics − XML-Based Web services use XML at data representation and data transportation layers. Using XML eliminates any networking, operating system, or platform binding. Web services based applications are highly interoperable at their core level. Loosely Coupled A consumer of a web service is not tied to that web service directly. The web service interface can change over time without compromising the client”s ability to interact with the service. A tightly coupled system implies that the client and server logic are closely tied to one another, implying that if one interface changes, the other must be updated. Adopting a loosely coupled architecture tends to make software systems more manageable and allows simpler integration between different systems. Coarse-Grained Object-oriented technologies such as Java expose their services through individual methods. An individual method is too fine an operation to provide any useful capability at a corporate level. Building a Java program from scratch requires the creation of several fine-grained methods that are then composed into a coarse-grained service that is consumed by either a client or another service. Businesses and the interfaces that they expose should be coarse-grained. Web services technology provides a natural way of defining coarse-grained services that access the right amount of business logic. Ability to be Synchronous or Asynchronous Synchronicity refers to the binding of the client to the execution of the service. In synchronous invocations, the client blocks and waits for the service to complete its operation before continuing. Asynchronous operations allow a client to invoke a service and then execute other functions. Asynchronous clients retrieve their result at a later point in time, while synchronous clients receive their result when the service has completed. Asynchronous capability is a key factor in enabling loosely coupled systems. Supports Remote Procedure Calls(RPCs) Web services allow clients to invoke procedures, functions, and methods on remote objects using an XML-based protocol. Remote procedures expose input and output parameters that a web service must support. Component development through Enterprise JavaBeans (EJBs) and .NET Components has increasingly become a part of architectures and enterprise deployments over the past couple of years. Both technologies are distributed and accessible through a variety of RPC mechanisms. A web service supports RPC by providing services of its own, equivalent to those of a traditional component, or by translating incoming invocations into an invocation of an EJB or a .NET component. Supports Document Exchange One of the key advantages of XML is its generic way of representing not only data, but also complex documents. These documents can be as simple as representing a current address, or they can be as complex as representing an entire book or Request for Quotation (RFQ). Web services support the transparent exchange of documents to facilitate business integration. Print Page Previous Next Advertisements ”;

What are Web Services? ”; Previous Next Different books and different organizations provide different definitions to Web Services. Some of them are listed here. A web service is any piece of software that makes itself available over the internet and uses a standardized XML messaging system. XML is used to encode all communications to a web service. For example, a client invokes a web service by sending an XML message, then waits for a corresponding XML response. As all communication is in XML, web services are not tied to any one operating system or programming language—Java can talk with Perl; Windows applications can talk with Unix applications. Web services are self-contained, modular, distributed, dynamic applications that can be described, published, located, or invoked over the network to create products, processes, and supply chains. These applications can be local, distributed, or web-based. Web services are built on top of open standards such as TCP/IP, HTTP, Java, HTML, and XML. Web services are XML-based information exchange systems that use the Internet for direct application-to-application interaction. These systems can include programs, objects, messages, or documents. A web service is a collection of open protocols and standards used for exchanging data between applications or systems. Software applications written in various programming languages and running on various platforms can use web services to exchange data over computer networks like the Internet in a manner similar to inter-process communication on a single computer. This interoperability (e.g., between Java and Python, or Windows and Linux applications) is due to the use of open standards. To summarize, a complete web service is, therefore, any service that − Is available over the Internet or private (intranet) networks Uses a standardized XML messaging system Is not tied to any one operating system or programming language Is self-describing via a common XML grammar Is discoverable via a simple find mechanism Components of Web Services The basic web services platform is XML &plus; HTTP. All the standard web services work using the following components − SOAP (Simple Object Access Protocol) UDDI (Universal Description, Discovery and Integration) WSDL (Web Services Description Language) All these components have been discussed in the Web Services Architecture chapter. How Does a Web Service Work? A web service enables communication among various applications by using open standards such as HTML, XML, WSDL, and SOAP. A web service takes the help of − XML to tag the data SOAP to transfer a message WSDL to describe the availability of service. You can build a Java-based web service on Solaris that is accessible from your Visual Basic program that runs on Windows. You can also use C# to build new web services on Windows that can be invoked from your web application that is based on JavaServer Pages (JSP) and runs on Linux. Example Consider a simple account-management and order processing system. The accounting personnel use a client application built with Visual Basic or JSP to create new accounts and enter new customer orders. The processing logic for this system is written in Java and resides on a Solaris machine, which also interacts with a database to store information. The steps to perform this operation are as follows − The client program bundles the account registration information into a SOAP message. This SOAP message is sent to the web service as the body of an HTTP POST request. The web service unpacks the SOAP request and converts it into a command that the application can understand. The application processes the information as required and responds with a new unique account number for that customer. Next, the web service packages the response into another SOAP message, which it sends back to the client program in response to its HTTP request. The client program unpacks the SOAP message to obtain the results of the account registration process. Print Page Previous Next Advertisements ”;

Web Services – Quick Guide ”; Previous Next What are Web Services? Different books and different organizations provide different definitions to Web Services. Some of them are listed here. A web service is any piece of software that makes itself available over the internet and uses a standardized XML messaging system. XML is used to encode all communications to a web service. For example, a client invokes a web service by sending an XML message, then waits for a corresponding XML response. As all communication is in XML, web services are not tied to any one operating system or programming language—Java can talk with Perl; Windows applications can talk with Unix applications. Web services are self-contained, modular, distributed, dynamic applications that can be described, published, located, or invoked over the network to create products, processes, and supply chains. These applications can be local, distributed, or web-based. Web services are built on top of open standards such as TCP/IP, HTTP, Java, HTML, and XML. Web services are XML-based information exchange systems that use the Internet for direct application-to-application interaction. These systems can include programs, objects, messages, or documents. A web service is a collection of open protocols and standards used for exchanging data between applications or systems. Software applications written in various programming languages and running on various platforms can use web services to exchange data over computer networks like the Internet in a manner similar to inter-process communication on a single computer. This interoperability (e.g., between Java and Python, or Windows and Linux applications) is due to the use of open standards. To summarize, a complete web service is, therefore, any service that − Is available over the Internet or private (intranet) networks Uses a standardized XML messaging system Is not tied to any one operating system or programming language Is self-describing via a common XML grammar Is discoverable via a simple find mechanism Components of Web Services The basic web services platform is XML &plus; HTTP. All the standard web services work using the following components − SOAP (Simple Object Access Protocol) UDDI (Universal Description, Discovery and Integration) WSDL (Web Services Description Language) All these components have been discussed in the Web Services Architecture chapter. How Does a Web Service Work? A web service enables communication among various applications by using open standards such as HTML, XML, WSDL, and SOAP. A web service takes the help of − XML to tag the data SOAP to transfer a message WSDL to describe the availability of service. You can build a Java-based web service on Solaris that is accessible from your Visual Basic program that runs on Windows. You can also use C# to build new web services on Windows that can be invoked from your web application that is based on JavaServer Pages (JSP) and runs on Linux. Example Consider a simple account-management and order processing system. The accounting personnel use a client application built with Visual Basic or JSP to create new accounts and enter new customer orders. The processing logic for this system is written in Java and resides on a Solaris machine, which also interacts with a database to store information. The steps to perform this operation are as follows − The client program bundles the account registration information into a SOAP message. This SOAP message is sent to the web service as the body of an HTTP POST request. The web service unpacks the SOAP request and converts it into a command that the application can understand. The application processes the information as required and responds with a new unique account number for that customer. Next, the web service packages the response into another SOAP message, which it sends back to the client program in response to its HTTP request. The client program unpacks the SOAP message to obtain the results of the account registration process. Why Web Services? Here are the benefits of using Web Services − Exposing the Existing Function on the network A web service is a unit of managed code that can be remotely invoked using HTTP. That is, it can be activated using HTTP requests. Web services allow you to expose the functionality of your existing code over the network. Once it is exposed on the network, other applications can use the functionality of your program. Interoperability Web services allow various applications to talk to each other and share data and services among themselves. Other applications can also use the web services. For example, a VB or .NET application can talk to Java web services and vice versa. Web services are used to make the application platform and technology independent. Standardized Protocol Web services use standardized industry standard protocol for the communication. All the four layers (Service Transport, XML Messaging, Service Description, and Service Discovery layers) use well-defined protocols in the web services protocol stack. This standardization of protocol stack gives the business many advantages such as a wide range of choices, reduction in the cost due to competition, and increase in the quality. Low Cost Communication Web services use SOAP over HTTP protocol, so you can use your existing low-cost internet for implementing web services. This solution is much less costly compared to proprietary solutions like EDI/B2B. Besides SOAP over HTTP, web services can also be implemented on other reliable transport mechanisms like FTP. Web Services – Characteristics Web services have the following special behavioral characteristics − XML-Based Web services use XML at data representation and data transportation layers. Using XML eliminates any networking, operating system, or platform binding. Web services based applications are highly interoperable at their core level. Loosely Coupled A consumer of a web service is not tied to that web service directly. The web service interface can change over time without compromising the client”s ability to interact with the service. A tightly coupled system implies that the client and server logic are closely tied to one another, implying that if one interface changes, the other must be updated. Adopting a loosely coupled

Web Services – Summary ”; Previous Next In this tutorial, you have learnt how to use web services. However, a web service also include components such as WSDL, UDDI, and SOAP that contribute to make it active. The next step is to learn WSDL, UDDI, and SOAP. WSDL WSDL is an XML-based language for describing web services and how to access them. WSDL describes a web service, along with the message format and protocol details for the web service. To learn more about WSDL, visit our WSDL Tutorial. UDDI UDDI is an XML-based standard for describing, publishing, and finding web services. To learn more about UDDI, visit our UDDI Tutorial. SOAP SOAP is a simple XML-based protocol that allows applications to exchange information over HTTP. To learn more about SOAP, visit our SOAP Tutorial. Print Page Previous Next Advertisements ”;

Web Services – Security ”; Previous Next Security is critical to web services. However, neither XML-RPC nor SOAP specifications make any explicit security or authentication requirements. There are three specific security issues with web services − Confidentiality Authentication Network Security Confidentiality If a client sends an XML request to a server, can we ensure that the communication remains confidential? Answer lies here − XML-RPC and SOAP run primarily on top of HTTP. HTTP has support for Secure Sockets Layer (SSL). Communication can be encrypted via SSL. SSL is a proven technology and widely deployed. A single web service may consist of a chain of applications. For example, one large service might tie together the services of three other applications. In this case, SSL is not adequate; the messages need to be encrypted at each node along the service path, and each node represents a potential weak link in the chain. Currently, there is no agreed-upon solution to this issue, but one promising solution is the W3C XML Encryption Standard. This standard provides a framework for encrypting and decrypting entire XML documents or just portions of an XML document. You can check it at www.w3.org/Encryption Authentication If a client connects to a web service, how do we identify the user? Is the user authorized to use the service? The following options can be considered but there is no clear consensus on a strong authentication scheme. HTTP includes built-in support for Basic and Digest authentication, and services can therefore be protected in much the same manner as HTML documents are currently protected. SOAP Digital Signature (SOAP-DSIG) leverages public key cryptography to digitally sign SOAP messages. It enables the client or server to validate the identity of the other party. Check it at www.w3.org/TR/SOAP-dsig. The Organization for the Advancement of Structured Information Standards (OASIS) is working on the Security Assertion Markup Language (SAML). Network Security There is currently no easy answer to this problem, and it has been the subject of much debate. For now, if you are truly intent on filtering out SOAP or XML-RPC messages, one possibility is to filter out all HTTP POST requests that set their content type to text/xml. Another alternative is to filter the SOAPAction HTTP header attribute. Firewall vendors are also currently developing tools explicitly designed to filter web service traffic. Print Page Previous Next Advertisements ”;

Web Services Tutorial PDF Version Quick Guide Resources Job Search Discussion Web services are open standard (XML, SOAP, HTTP, etc.) based web applications that interact with other web applications for the purpose of exchanging data. Web services can convert your existing applications into web applications. In this tutorial, you will learn what exactly web services are and why and how to use them. Audience This tutorial will be useful for all those readers inclined to learn the basics of web services and implement them in practice. Prerequisites This is an elementary tutorial that introduces the concepts of web services. It does not require the readers to have a prior knowledge of any technology in particular, however it would certainly make you comfortable if you have a basic understanding of XML, HTTP, TCP/IP concepts. Print Page Previous Next Advertisements ”;