OData RESTful implementation
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This document discusses REST web services and the OData protocol. It provides an overview of REST principles like being stateless and using a uniform interface. OData is described as a protocol that solves specific problems in REST API design by allowing resources to be queried and linked together. The document then shows an example of implementing an OData service in C# using Entity Framework with CRUD operations and OData query options like $filter, $expand, $select and $orderby. In the example, blog posts and post types are exposed as OData resources that can be queried and linked together.
OData RESTful implementation
- 2. REST WEB SERVICES Β» SOAP (Service Oriented) and REST (Resource Oriented) Β» REpresentational State Transfer Β» REST Principles: Client-Server, Stateless, Cacheable, Layered system, Code on demand, Uniform Interface, Identification of resources, Manipulation of resources, self-descriptive messages Β» REST API is an architecture that adheres to the above principles. Β» Simple words: JSON interaction with a client application. Content negotiation made clearer using REST. Β» ODATA is a protocol. It solves specific problem faced in REST API design.
- 3. ODATA KEY FEATURES OVER WEB API β’ Query able and Interoperable RESTful API β’ Containment of Dependent Objects (Child Objects) β’ Deferred Execution β’ Easy Query Conventions β’ Powerful data reading capability
- 4. ODATA REST IMPLEMENTATION EXAMPLE I will be showing an example where I implemented an OData Service. I will be focussing mainly on the HTTP GET of the ODATA. The next following pages will be: β’ Tables used for this example β’ OData REST page using swagger integration. β’ Queries used with example β’ Project Settings
- 5. TABLES USED
- 6. MY ODATA REST SERVICE PAGE
- 7. $SELECT
- 8. $TOP
- 9. $SKIP
- 10. $EXPAND $expand Query: Posts($select=Title;$expand=TypeOfPosts($select=Type)) Post (Child entity of Blog) & TypeOfPost (Child entity of Post) Note: Refer table diagram in Slide 5 for tablesβ relationship. Response Body is shown partially below.
- 11. $COUNT
- 12. $ORDERBY
- 13. $FILTER This particular query can be used in various combinations. β’ Comparative $filter - contains, eq β equal, ne- not equals, lt β less than, gt β greater than, le β less than and equals, ge- greater than and equals β’ Nested $filter - $filter used against other query options. (e.g. $expand with $filter) β’ Conditional $filter - and, or, not β’ Lambda/anonymous $filter β any, all β’ Arithmetic $filter - Add β addition , mul β multiplication , div β division , sub β subtraction . NOTE: Arithmetic and Conditional $filter will not have my project example as they do not relate to my sample ODATA project. I have provided another suitable example.
- 14. COMPARATIVE $FILTER Reverse lookup example: contains(Name, βselβ) Another example: Name eq βRussell Watsonβ NESTED $FILTER CONDITIONAL $FILTER Example: $filter = (Section eq βITβ) and not (SubjectCode eq β10026β)
- 15. LAMBDA $FILTER Another example: Posts/any(vr:vr/Title eq βIOO1β) Example: $filter = AmountOfCash div NumberOfRecords gt 10 ARITHMETIC $Filter
- 17. CREATE DEFAULT MVC WEB API
- 18. ADD NEW CONTROLLER FOR ODATA
- 20. DB CONTEXT
- 21. MODIFY ODATA CONTROLLER NOTE: By default, Odata Controllerβs Enable Query retrieves inline entities up to 2 levels. More than 2 levels need to be mentioned explicitly by Max Expansion Depth.
- 22. ODATA CONFIG
- 23. SWAGGER CONFIG (OPTIONAL) NOTE: This setting will be needed if you want to test this in swagger tool.
- 24. WEB API CONFIG
- 25. GLOBAL ASAX
- 26. SUMMARY By the end of this presentation, I hope you can make use of ODATA in a RESTful manner. OData has been for many years and has been overly underrated. With this presentation, we have covered: β’ REST service β’ Highlights of ODATA β’ ODATA Implementation β’ ODATA Query options β’ ODATA Project setup Please have a read through in the blog for OData for more information. https://www.odata.org/ THANK YOU