rest-api introduction for developers

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  1. 1. Super simple introduction to REST-APIs For programmers By Patrick Savalle, innovation architect Delta Lloyd NV.
  4. 4. REST is HTTP/1.1. It is the native protocol of the web. Advantages are: Every tool that can handle Web / HTTP, can handle REST as native content. For instance gateways, web-servers and browsers can effectively cache, route, verify, manipulate REST requests or responses. In short the whole web supports REST It is simple and elegant Less diversity in technology, you already use HTTP Part1:~ Http$ WHY REST?_ REST is HTTP. It is the same protocol. Created by the same designer.
  5. 5. Part1:~ Http$ PROTOCOL_ HTTP is a plain text conversation between a client and a server. The conversation is based on actions performed on resources which are addressed by URLs.
  6. 6. Part1:~ Http$ URL_ Every resource has an unique URL that consists of several parts.
  7. 7. Part1:~ Http$ VERBS_ The actions that can be performed on a resource are called methods or verbs. Below the most used verbs (there are many more). POST create PUT update DELETE delete GET read PATCH partial update TRACE echo HEAD headers only
  8. 8. Part1:~ Http$ Request_ Requests and responses contain header-fields and possibly content. Everything is plain text. Headers usually contain metadata or indicate conversation preferences.
  10. 10. Part1:~ Http$ STATUS CODES_ Every response contains a status code.
  11. 11. PART 2 REST BASICS
  12. 12. Part2:~ Rest$ ENDPOINTS_ The REST protocol is based on endpoints, which are operations on resources addressed by URLs. Endpoints can be bundled to form an API.
  13. 13. ACTION RESOURCE https:///[//] GET https://animal.api/1/lions (returns collection) GET https://animal.api/1/lions/ (returns single lion) POST https://animal.api/1/lions (create new element) PUT https://animal.api/1/lions/ (updates element) PATCH https://animal.api/1/lions/ (partial update) DELETE https://animal.api/1/lions (deletes collection) DELETE https://animal.api/1/lions/ (deletes single element) GET GET https://animal.api/1/lions?start=100&count=50 GET https://animal.api/1/lions?id=100&id=103&id=107 (parameter-array) Part2:~ Rest$ ACTION + RESOURCE_ An endpoint has a very strict URL structure. This is key to REST. Map your functional application resources onto the WWW and allow them to be manipulated.
  14. 14. Part2:~ Rest$ ANTI-PATTERNS_ REST is not SOAP. An URL is NOT a RPC-address or method, it is an universal RESOURCE locator Bad REST API (bad URLs in general): POST POST POST Good REST API: PUT DELETE POST GET
  15. 15. AUTHENTICATION HTTP BASIC AUTH Client sends user/password in special header with each API-call. Simple, safe, good choice for API-2-API TOKEN AUTH Get a temporary access token from API, use in API-calls in username part of HTTP BACIS AUTH, simple, safe, good choice for WEB-2-API OAUTH2 Industry standard. Flexible. Safe. Part2:~ Rest$ AUTHENTICATION_
  16. 16. Part2:~ Rest$ JAVA EXAMPLE_ HttpResponse jsonResponse = Unirest .post("") .header("accept", "application/json") .queryString("apiKey", "123") .field("parameter", "value") .field("foo", "bar") .asJson();
  17. 17. PART 3 API BASICS
  18. 18. Part3:~ Api$ RULE NUMBER ONE_ A REST-server must be client-state agnostic! To be flexible and scalable the server needs to be ignorant of client-state or context. A REST-server does not store session data on behalf of the client. Put another way: all necessary context MUST be in the request. As far as the REST-server is concerned every call is the first call.
  19. 19. Part3:~ Api$ Economy_ There is an API for that. REST-APIs are the glue of the Internet of Things.
  20. 20. Possible clients of your API: Other APIs Web applications and web front ends (like AngularJS, ReactJS, JQuery web apps) Mobile apps, applications etc. Machines, bots Typically NOT humans or end users APIs are the glue of the internet of things (IoT). Part3:~ Api$ Users_ On the internet nobody knows youre a machine.
  21. 21. Coherent Cohesive (Only lists purposeful endpoints) Complete (has all necessary endpoints for its purpose) Minimal (Only one way to do things) Encapsulating (hiding implementation details) Self-explaining Documented! Design an API outside-in, as a product for a generic client. Not just as the library for your specific front-end. Consider adding the role interface designer to the team. Part3:~ Api$ Interface quality_ Good interface design is crafmanship.
  22. 22. The API Endpoint documentation A dashboard to register apps / obtain an API-key Language stubs (Java, PHP, Python, etc.) on Github Registration on programmableweb and similar A homepage / productpage A revenue-model / pricing A launchparty Hackathons Part3:~ Api$ deliverables_ An API is a product, treat it as such.
  23. 23. Some of the choices only you can make: Few methods / large responses vs. many methods / small responses Considerations: web clients generally like large aggregated responses tailored to their page structures. Other clients like smaller responses. Etc. There is also the underlying (logical) data model and the natural granularity of the problem-domain. In most cases: map the data model onto URLs. URL parameters vs request headers (for instance the API-tokens) Considerations: in general non-functional data should be in headers. Headers are more easily inspected / used by tools like webservers, giving transport flexibility. Hypermedia communication (follow-up URLs in responses, HATEOAS) Problematic concept, very client dependent. Most APIs dont have this, why should yours? Part3:~ Api$ Interface choices_ Good interface design is crafmanship.
  24. 24. A REST client, e.g. the Chrome POSTMAN plugin (most IDEs have one as an add-on) TELNET (the generic HTTP client) Part3:~ Api$ RESOURCES_