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OData

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Web Services

o    is a collection of standards or protocols for exchanging information between two devices or application

o    method of communication between two devices over network

o    is a client server application or application component for communication

    There are mainly two types of web services.
    1. SOAP web services.
    2. RESTful web services.

    SOAP Web Services

    SOAP stands for Simple Object Access Protocol. It is a XML-based protocol for accessing web services.
    SOAP is a W3C recommendation for communication between two applications.
    SOAP is XML based protocol. It is platform independent and language independent.

    Advantages of Soap Web Services

    WS Security: SOAP defines its own security known as WS Security.
    Language and Platform independent: SOAP web services can be written in any programming language and executed in any platform

    Disadvantages of Soap Web Services

    Slow: SOAP uses XML format that must be parsed to be read. It defines many standards that must be followed while developing the SOAP applications. So it is slow and consumes more bandwidth and resource.
    WSDL dependent: SOAP uses WSDL and doesn't have any other mechanism to discover the service.

    RESTful Web Services

    REST stands for Representational State Transfer.
    REST is an architectural style not a protocol.

    Advantages of RESTful Web Services

    Fast: RESTful Web Services are fast because there is no strict specification like SOAP. It consumes less bandwidth and resource.
    Language and Platform independent: RESTful web services can be written in any programming language and executed in any platform.
    Can use SOAP: RESTful web services can use SOAP web services as the implementation.
    Permits different data format: RESTful web service permits different data format such as Plain Text, HTML, XML and JSON.
    There are three major web service componentes.
    1. SOAP
    2. WSDL
    3. UDDI

    SOAP

    SOAP is an acronym for Simple Object Access Protocol.
    SOAP is a XML-based protocol for accessing web services.
    SOAP is a W3C recommendation for communication between applications.
    SOAP is XML based, so it is platform independent and language independent. In other words, it can be used with Java, .Net or PHP language on any platform.

    WSDL

    WSDL is an acronym for Web Services Description Language.
    WSDL is a xml document containing information about web services such as method name, method parameter and how to access it.
    WSDL is a part of UDDI. It acts as a interface between web service applications.
    WSDL is pronounced as wiz-dull.

    UDDI

    UDDI is an acronym for Universal Description, Discovery and Integration.
    UDDI is a XML based framework for describing, discovering and integrating web services.
    UDDI is a directory of web service interfaces described by WSDL, containing information about web services

    SOAP vs REST 
    1.     SOAP is a protocol and REST is an architectural style.
    2.     SOAP stands for Simple Object Access Protocol and REST stands for REpresentational State Transfer
    3.     SOAP can't use REST because it is a protocol and REST can use SOAP web services because it is a concept and
     can use any protocol like HTTP, SOAP
    4.     SOAP permits XML data format only and REST permits different data format such as Plain text,HTML, XML, JSON etc
    5.     SOAP is less preferred than REST and REST more preferred than SOAP

    Service Oriented Architecture (SOA)

    Service Oriented Architecture or SOA is a design pattern. It is designed to provide services to other applications through protocol. It is a concept only and not tied to any programming language or platform.

    Web services is a technology of SOA most likely.

    Service

    A service is well-defined, self-contained function that represents unit of functionality. A service can exchange information from another service. It is not dependent on the state of another service.

    OData
    1.   Acronym for “Open Data Protocol”.
    2.   OData is also called as ODBC i.e. open database connectivity of the web.
    3.    ODBC is a standard API to access the DBMS, independent of the database management systems or operating systems.
    4.   ODBC achieves this by adding drivers between the Application layer and the DBMS to translate the queries requested by the applications into instructions which DBMS can understand.
    5.   OData acts like middleware between producers and consumers to communicate data.
    6.     OData interface is an open standard that can be consumed by any Application, program, software or device of the Non-SAP world that can connect with SAP using the HTTP(s) protocol.
    7.   It’s an implementation of HTTP(s).

    Why OData?
    1.    Before OData there was point-to-point solution for SAP to NON-SAP integration.
    2.    One application with two different platforms needed two different design.
    This means there was following drawbacks:
    a.    Increased Administrative Effort.
    b.    Increased system landscape Complexity         
    3.Alternative to point-to-point solution is One Data Model-> 
    One API-Multiple End User Experiences

    This approach provides one solution to any environment,any platform.
    No SAP knowledge is required for the consumption of OData.
    HTTP CODES
    1XX: Informational
    It means the request has been received and the process is continuing.
    2XX: Success
    It means the action was successfully received, understood, and accepted.
    3XX: Redirection
    It means further action must be taken in order to complete the request. 
    4XX: Client Error
    It means the request contains incorrect syntax or cannot be fulfilled.
    5XX: Server Error
    It means the server failed to fulfill an apparently valid request.
    System Query
        System Query Options are query string parameters a client may specify to control the amount and order of the data that an OData service returns for the resource identified by the URL.The names of all System Query Options are prefixed with a “$” character.
        Example: $select, $filter, $top, $skip, $expand etc
    Clause
        It is simple condition which we provide after System query options For Ex: https://services.odata.org/OData/OData.svc/Products?$select=Rating,ReleaseDate&$format=json                                                   
    Here Rating and ReleaseDate are clauses  
    3 Tier Architecture 
    SAP NetWeaver Gateway                             
    a. It is used to setup a connection between SAP business suite and target clients, platforms and framework. It offers development and generation tools to create OData services to different client development tools.
    b. It’s a technology that offers connectivity to SAP Business data using any programming language and without the need of strong SAP Development knowledge.
    c.  SAP Netweaver Gateway sits on top of the existing SAP Backend infrastructure.
    d.  SAP Netweaver Gateway comes with design-time tools to facilitate modeling OData services for consumption. These tools improve user experience and provide automatic connectivity to the SAP backend that reduces development efforts and improves productivity.
    e. There are set of add-on components that needs to be installed on a SAP Backend system to enable SAP Netweaver Gateway services.
        At 7.3 and before 7.3: GW_CORE, IW_FND used for Gateway server functionality and IW_BEP was used for Gateway Backend Functionality. 
        After 7.4 release: All the three component bundled together called GW_FND Gateway Foundation. 
    f. It is this architecture that enables consumption of SAP data by variety of interfaces such as BAPIs and RFCs.
    Deployment Options

    a. Hub Deployment: Development in the Backend system  

    b. Hub Deployment: Development in the Hub

    C. Embedded Deployment
               SICF
    a. It’s a tcode for SAP webserver Administration Transaction. 
    b. The Internet Communication Manager ensures the communication between SAP NetWeaver Application server and the Web Browser.
    c.  It exists as a service within SAP NetWeaver Application Server.
    SAP NetWeaver Gateway Service Builder tool
    SAP NetWeaver Gateway Service Builder tool is SAP GUI Based Modeler to create and publish OData services using transaction SEGW.
    Object Navigator(SE80)
    All the objects like FM, reports, Structure etc. will be available here under the name of Package.
    The Package is captured in a TR i.e. Transport Request.

    LET'S CRUD

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