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OData Services
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- 2. Jovan Popovic Program managerMDCS/SQL Server/Azure Azure/SQL/ASP.NET/JQuery PhD Electrical Engineering http://petlja.rs/
- 3. Agenda • REST • WhyOData? • OData – details • Demo
- 4. What is REST? •Way of providing interoperability between computer systems on the Internet • Stateless access on resources by Uri • CRUD operations via HTTP methods • POST – Create resource • GET – Read resource • PUT – Update resource • DELETE – Delete resource
- 5. Problem – CustomREST Endpoints • Clients need many custom queries. • How to serve custom requests? • Using custom Url • /Company/ByName/Acme • /CompanyByRegion(‘Serbia’) • Using custom parameters • /Company?Name=Acme • /Company?Region=Serbia
- 6. SQL language • HowDatabases solve this problem? • SQL Language • SELECT <columns> • WHERE <condition> • ORDER BY <columns> • OFFSET <skip> • FETCH <top>
- 7. Idea: SQL ontop of REST • Adding query clauses as parameters • $select= • $filter= • $orderby= • $take= • $skip= • OData standardizes query clauses • Two types of parameters • OData reserved parameters beginning with $ • Reserved for future usage • Custom app-specific parameters cannot start with $ • You can put any parameter
- 8. OData specification • Microsoftinitiated OData in 2007. • Versions 1.0, 2.0, and 3.0 are released under the Microsoft Open Specification Promise. • Version 4.0 was standardized at OASIS, March 2014. • Standardized as ISO/IEC 20802:1 and 20801:2 • OData contributors • Citrix Systems, IBM, Microsoft, Progress Software, Red Hat, SAP.
- 9. OData queries How toquery data via OData REST API
- 10. Output formats • ODataspecifies the output format • JSON(default) • XML • Response may include metadata • odata.metadata=minimal • odata.metadata=full • odata.metadata=none • Metadata may be used by client to understand data types in response and generate client code (if needed)
- 11. Resources • OData hastop-level resources • http://services.odata.org/TripPinRESTierService/People • http://services.odata.org/TripPinRESTierService/Airlines • http://services.odata.org/TripPinRESTierService/Airports • Fetching resources by id/key • http://services.odata.org/TripPinRESTierService/Airports('KSFO’) • http://services.odata.org/TripPinRESTierService/People('russellwhyte’)
- 12. Querying data with$filter • Relational expressions • eq, ne, gt, lt, le, ge • Logical expression • and, or, not • Examples • http://services.odata.org/TripPinRESTierService/People?$filter=FirstName eq 'Scott' • http://services.odata.org/TripPinRESTierService/People?$filter=FirstName eq 'Scott' or FirstName eq 'Russell'
- 13. Ordering results with$orderby • Use any column and include direction (asc or desc) • Examples • http://services.odata.org/TripPinRESTierService/People?$orderby=FirstName • http://services.odata.org/TripPinRESTierService/People?$orderby=FirstName desc
- 14. Pagination • Pagination parameters$skip and $top • Example • http://services.odata.org/TripPinRESTierService/People?$skip=30&$top=10
- 15. Expansion • Include relatedentities with $expand parameter • Examples • http://services.odata.org/TripPinRESTierService/People('keithpinckney')?$exp and=Trips • http://services.odata.org/TripPinRESTierService/People('russellwhyte')?$expa nd=Trips($top=1) • http://services.odata.org/TripPinRESTierService/People('russellwhyte')?$expa nd=Trips($filter=Name eq 'Trip in US’)
- 16. Functions and Actions •Non-resource oriented REST Endpoints • Example • http://services.odata.org/TripPinRESTierService/GetNearestAirport(lat = 33, lon = -118)
- 17. OData ecosystem Client toolsand server API
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- 19. Demo time How tobuild applications using OData services?
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- 21. o.js o('StockItems') .select("StockItemName,UnitPrice,TaxRate,ColorName,Size,Brand") .where("UnitPrice lt 20") .orderBy("UnitPrice","asc") .skip(20) .take(10) .get(data => $(".product-item").view(data) );
- 22. References • http://www.odata.org • Intro •Understand OData in 6-steps • Libraries • JavaScript Clients: olingo, o.js • OData vs GraphQL vs ORDS • OData Services in .NET(Code Project)