Web Services Kanda Runapongsa Dept. of Computer Engineering Khon Kaen University

168493: XML and Web Services (II/2546) 2 What are Web Services? Web services are loosely coupled software components delivered over Internet standard technologies Facilitate delivering business applications as a service accessible to anyone, anytime, at any location, and using any platform

168493: XML and Web Services (II/2546) 3 Web Services Characteristics Based on XML messaging Data exchanged between the Web service provider and the user are defined in XML Web services provide a cross- platform integration of business applications over the Internet

168493: XML and Web Services (II/2546) 4 Web Services Characteristics To build Web services, developers can use any common programming language, such as Java, C, C++, Perl, Python, C#, and /or Visual Basic Web services can be used by many types of clients on various types of devices, such as Wireless device, PDA, Desktop, Automobile

168493: XML and Web Services (II/2546) 5 Web Services Characteristics Web services vary in functionality from a simple request to a complex business transaction involving multiple resources All platforms including J2EE, CORBA, and Microsoft.NET provide extensive support for creating and deploying Web services

168493: XML and Web Services (II/2546) 6 Web Services Characteristics Web services use industry-standard protocols like HTTP, and they can be easily accessible through corporate firewalls Web services are dynamically located and invoked from public and private registries based on industry standards such as UDDI and ebXML

168493: XML and Web Services (II/2546) 7 Web Applications vs. Web Services Traditionally, Web applications enable interaction between an end user and a Web site Web Services are service-oriented and enable application-to-application communication over the Internet and easy accessibility to heterogeneous applications and devices

168493: XML and Web Services (II/2546) 8 Why Use Web Services? Can be invoked through XML-based RPC mechanisms across firewalls Provide a cross-platform, cross-language solution based on XML messaging Facilitate ease of application integration using a light-weight infrastructure without affecting scalability Enable interoperability among heterogeneous applications

168493: XML and Web Services (II/2546) 9 Operational Model of Web Services Discover Service Service Broker Service Requestor Service Provider Register Service Invoke Service

168493: XML and Web Services (II/2546) 10 Operational Model of Web Services Service provider Developing and deploying the Web services Define the services and publishes them with the service broker Service broker (service registry) List various service types, descriptions, and locations of the services that help the service requesters find and subscribe to the required services

168493: XML and Web Services (II/2546) 11 Operational Model of Web Services Service requestor Locate the Web service using the service broker Invoke the required services Execute the services from the service provider

168493: XML and Web Services (II/2546) 12 Web Services Communication Models In Web services architecture, the communication models can be RPC-based synchronous Messaging-based synchronous/asynchronous

168493: XML and Web Services (II/2546) 13 RPC-Based Communication Model Define a request/response-based synchronous communication When the client sends a request, the client waits until a response is sent back from the server before continuing any operation Service Requester Service Provider REQUEST RESPONSE

168493: XML and Web Services (II/2546) 14 RPC-Based Communication Model Clients invoke the Web services by sending parameter values to the Web service provider The Web service provider executes the required method and sends back the return values

168493: XML and Web Services (II/2546) 15 Messaging-based Communication Model Define a loosely coupled and document-driven communication The service requestor does not wait for a response Service Requester Service Provider MESSAGE

168493: XML and Web Services (II/2546) 16 Messaging-based Communication Model The client sends an entire document rather than sending a set of parameters The service provider receives the document, processes it, and then may or may not return a message With a synchronous model, the client can request a service, then wait, and receive the document from the service provider

168493: XML and Web Services (II/2546) 17 Implementing Web Services 1. The service provider Creates the Web service typically as SOAP-based service interfaces Deploys the service and make them available for invocation over a network Describes the Web service as a WSDL- based service description

168493: XML and Web Services (II/2546) 18 Implementing Web Services 2. The service provider Registers the WSDL-based service description with a service broker, which is typically a UDDI registry 3. The UDDI registry Stores the service description as binding templates and URLs to WSDLs located in the service provider environment

168493: XML and Web Services (II/2546) 19 Implementing Web Services 4. The service requestor Locates the required services by querying the UDDI registry Obtains the binding information and the URLs to identify the service provider 5. The service requestor Invokes the service provider Retrieves the WSDL Service description for those registered services

168493: XML and Web Services (II/2546) 20 Implementing Web Services 6. The service requestor Communicate with the service provider Exchange data or messages by invoking the available services in the service container

168493: XML and Web Services (II/2546) 21 Implementing Web Services Service Broker Service Requestor Service Provider 1. Create Web Service and WSDL 2. Register/Publish Services 3. Store service description 4. Locate services and its binding info 5. Invoke & obtain WSDL 6. Exchange data using SOAP RPC/Messaging

168493: XML and Web Services (II/2546) 22 Building Web Services in the J2EE Environment Sun released its Java API for Web Services for the developer community as the Java Web Services Developer Pack (JWSDP) It provides a full-fledged solution package for developing and testing Web services using the Java APIs, such as JAXM, JAXP, JAXR, JAXB, JAX-RPC, Java WSDP Register Server, and JSTL Apache released Apache Axis as a tool for creating and testing Web services