REST API Design for JAX-RS And Jersey

Designing and building a really clean and intuitive ReST API is no small feat. You have to worry about resources, collections of resources, pagination, query parameters, references to other resources, which HTTP methods to use, HTTP caching, security, and more. And you have to make sure it lasts and doesn’t break clients as you add features over time. Furthermore, although there are many references on creating REST APIs with XML, there are far fewer references on REST + JSON. It is enough to drive you crazy. This session demonstrates how to design and implement an elegant REST API.

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Transcript

1. REST + JSON APIs with JAX-RS Les Hazlewood CTO, Stormpath stormpath.com
2. .com • Identity Management and Access Control API • Security for your applications • User security workflows • Security best practices • Developer tools, SDKs, libraries
3. Outline • REST Fundamentals • Design: Base URL Versioning Resource Format Return Values Content Negotiation References (Linking) Pagination Query Parameters Associations Errors IDs Method Overloading Resource Expansion Partial Responses Caching & Etags Security Multi Tenancy Maintenance • Coding Time! (JAX-RS-based App)
4. Why REST? • Scalability • Generality • Independence • Latency (Caching) • Security • Encapsulation Learn more at Stormpath.com
5. HATEOAS • Hypermedia • As • The • Engine • Of • Application • State Further restriction on REST architectures. Learn more at Stormpath.com
6. REST Is Easy Learn more at Stormpath.com
7. REST Is *&@#$! Hard (for providers) Learn more at Stormpath.com
8. REST can be easy (if you follow some guidelines) Learn more at Stormpath.com
9. Example Domain: Stormpath • Applications • Directories • Accounts • Groups • Associations • Workflows
10. Fundamentals Learn more at Stormpath.com
11. Resources Nouns, not Verbs Coarse Grained, not Fine Grained Architectural style for use-case scalability Learn more at Stormpath.com
12. /getAccount /createDirectory /updateGroup /verifyAccountEmailAddress What If? Learn more at Stormpath.com
13. /getAccount /getAllAccounts /searchAccounts /createDirectory /createLdapDirectory /updateGroup /updateGroupName /findGroupsByDirectory /searchGroupsByName /verifyAccountEmailAddress /verifyAccountEmailAddressByToken … Smells like bad RPC. DON’T DO THIS. What If? Learn more at Stormpath.com
14. Keep It Simple Learn more at Stormpath.com
15. The Answer Fundamentally two types of resources: Collection Resource Instance Resource Learn more at Stormpath.com
16. Collection Resource /applications Learn more at Stormpath.com
17. Instance Resource /applications/a1b2c3 Learn more at Stormpath.com
18. Behavior • GET • PUT • POST • DELETE • HEAD Learn more at Stormpath.com
19. Behavior POST, GET, PUT, DELETE ≠ 1:1 Create, Read, Update, Delete Learn more at Stormpath.com
20. Behavior As you would expect: GET = Read DELETE = Delete HEAD = Headers, no Body Learn more at Stormpath.com
21. Behavior Not so obvious: PUT and POST can both be used for Create and Update Learn more at Stormpath.com
22. PUT for Create Identifier is known by the client: PUT /applications/clientSpecifiedId { … } Learn more at Stormpath.com
23. PUT for Update Full Replacement PUT /applications/existingId { “name”: “Best App Ever”, “description”: “Awesomeness” } Learn more at Stormpath.com
24. PUT Idempotent Learn more at Stormpath.com
25. POST as Create On a parent resource POST /applications { “name”: “Best App Ever” } Response: 201 Created Location: https://api.stormpath.com/applications/a1b2c3 Learn more at Stormpath.com
26. POST as Update On instance resource POST /applications/a1b2c3 { “name”: “Best App Ever. Srsly.” } Response: 200 OK Learn more at Stormpath.com
27. POST NOT Idempotent Learn more at Stormpath.com
28. Media Types • Format Specification + Parsing Rules • Request: Accept header • Response: Content-Type header • application/json • application/foo+json • application/foo+json;application • … Learn more at Stormpath.com
29. Design Time! Learn more at Stormpath.com
30. Base URL Learn more at Stormpath.com
31. http(s)://api.foo.com vs http://www.foo.com/dev/service/api/r est Learn more at Stormpath.com
32. http(s)://api.foo.com Rest Client vs Browser Learn more at Stormpath.com
33. Versioning Learn more at Stormpath.com
34. URL https://api.stormpath.com/v1 vs. Media-Type application/json+foo;application&v=1 Learn more at Stormpath.com
35. Resource Format Learn more at Stormpath.com
36. Media Type Content-Type: application/json When time allows: application/foo+json application/foo+json;bar=baz&v=1 … Learn more at Stormpath.com
37. camelCase ‘JS’ in ‘JSON’ = JavaScript myArray.forEach Not myArray.for_each account.givenName Not account.given_name Underscores for property/function names are unconventional for JS. Stay consistent. Learn more at Stormpath.com
38. Date/Time/Timestamp There’s already a standard. Use it: ISO 8601 Example: { …, “createdTimestamp”: “2012-07-10T18:02:24.343Z” } Use UTC! Learn more at Stormpath.com
39. HREF • Distributed Hypermedia is paramount! • Every accessible Resource has a unique URL. • Replaces IDs (IDs exist, but are opaque). { “href”: https://api.stormpath.com/v1/accounts/x7y8z9”, … } Critical for linking, as we’ll soon see Learn more at Stormpath.com
40. Response Body Learn more at Stormpath.com
41. GET obvious What about POST? Return the representation in the response when feasible. Add override (?_body=false) for control Learn more at Stormpath.com
42. Content Negotiation Learn more at Stormpath.com
43. Header • Accept header • Header values comma delimited in order of preference GET /applications/a1b2c3 Accept: application/json, text/plain Learn more at Stormpath.com
44. Resource Extension /applications/a1b2c3.json /applications/a1b2c3.csv … Conventionally overrides Accept header Learn more at Stormpath.com
45. Resource References aka ‘Linking’ Learn more at Stormpath.com
46. • Hypermedia is paramount. • Linking is fundamental to scalability. • Tricky in JSON • XML has it (XLink), JSON doesn’t • How do we do it? Learn more at Stormpath.com
47. Instance Reference GET /accounts/x7y8z9 200 OK { “href”: “https://api.stormpath.com/v1/accounts/x7y8z9”, “givenName”: “Tony”, “surname”: “Stark”, …, “directory”: ???? } Learn more at Stormpath.com
48. Instance Reference GET /accounts/x7y8z9 200 OK { “href”: “https://api.stormpath.com/v1/accounts/x7y8z9”, “givenName”: “Tony”, “surname”: “Stark”, …, “directory”: { “href”: “https://api.stormpath.com/v1/directories/g4h5i6” } } Learn more at Stormpath.com
49. Collection Reference GET /accounts/x7y8z9 200 OK { “href”: “https://api.stormpath.com/v1/accounts/x7y8z9”, “givenName”: “Tony”, “surname”: “Stark”, …, “groups”: { “href”: “https://api.stormpath.com/v1/accounts/x7y8z9/groups” } } Learn more at Stormpath.com
50. Reference Expansion (aka Entity Expansion, Link Expansion) Learn more at Stormpath.com
51. Account and its Directory? Learn more at Stormpath.com
52. GET /accounts/x7y8z9?expand=directory 200 OK { “href”: “https://api.stormpath.com/v1/accounts/x7y8z9”, “givenName”: “Tony”, “surname”: “Stark”, …, “directory”: { “href”: “https://api.stormpath.com/v1/directories/g4h5i6”, “name”: “Avengers”, “creationDate”: “2012-07-01T14:22:18.029Z”, … } } Learn more at Stormpath.com
53. Partial Representations Learn more at Stormpath.com
54. GET /accounts/x7y8z9?fields=givenName,surname, directory(name) Learn more at Stormpath.com
55. Pagination Learn more at Stormpath.com
56. Collection Resource supports query params: • Offset • Limit …/applications?offset=50&limit=25 Learn more at Stormpath.com
57. GET /accounts/x7y8z9/groups 200 OK { “href”: “…/accounts/x7y8z9/groups”, “offset”: 0, “limit”: 25, “first”: { “href”: “…/accounts/x7y8z9/groups?offset=0” }, “previous”: null, “next”: { “href”: “…/accounts/x7y8z9/groups?offset=25” }, “last”: { “href”: “…”}, “items”: [ { “href”: “…” }, { “href”: “…” }, … ] } Learn more at Stormpath.com
58. Many To Many Learn more at Stormpath.com
59. Group to Account • A group can have many accounts • An account can be in many groups • Each mapping is a resource: GroupMembership Learn more at Stormpath.com
60. GET /groupMemberships/23lk3j2j3 200 OK { “href”: “…/groupMemberships/23lk3j2j3”, “account”: { “href”: “…” }, “group”: { “href”: “…” }, … } Learn more at Stormpath.com
61. GET /accounts/x7y8z9 200 OK { “href”: “…/accounts/x7y8z9”, “givenName”: “Tony”, “surname”: “Stark”, …, “groups”: { “href”: “…/accounts/x7y8z9/groups” }, “groupMemberships”: { “href”: “…/groupMemberships?accountId=x7y8z9” } } Learn more at Stormpath.com
62. Errors Learn more at Stormpath.com
63. • As descriptive as possible • As much information as possible • Developers are your customers Learn more at Stormpath.com
64. POST /directories 409 Conflict { “status”: 409, “code”: 40924, “property”: “name”, “message”: “A Directory named ‘Avengers’ already exists.”, “developerMessage”: “A directory named ‘Avengers’ already exists. If you have a stale local cache, please expire it now.”, “moreInfo”: “https://www.stormpath.com/docs/api/errors/4092 4” } Learn more at Stormpath.com
65. Security Learn more at Stormpath.com
66. Avoid sessions when possible Authenticate every request if necessary Stateless Authorize based on resource content, NOT URL! Use Existing Protocol: Oauth 1.0a, Oauth2, Basic over SSL only Custom Authentication Scheme: Only if you provide client code / SDK Only if you really, really know what you’re doing Use API Keys instead of Username/Passwords Learn more at Stormpath.com
67. HTTP Authentication Schemes • Server response to issue challenge: WWW-Authenticate: <scheme name> realm=“Application Name” • Client request to submit credentials: Authorization: <scheme name> <data> Learn more at Stormpath.com
68. 401 vs 403 • 401 “Unauthorized” really means Unauthenticated “You need valid credentials for me to respond to this request” • 403 “Forbidden” really means Unauthorized “I understood your credentials, but so sorry, you’re not allowed!” Learn more at Stormpath.com
69. API Keys • Entropy • Password Reset • Independence • Speed • Limited Exposure • Traceability Learn more at Stormpath.com
70. IDs Learn more at Stormpath.com
71. • IDs should be opaque • Should be globally unique • Avoid sequential numbers (contention, fusking) • Good candidates: UUIDs, ‘Url64’ Learn more at Stormpath.com
72. HTTP Method Overrides Learn more at Stormpath.com
73. POST /accounts/x7y8z9?_method=DELETE Learn more at Stormpath.com
74. Caching & Concurrency Control Learn more at Stormpath.com
75. Server (initial response): ETag: "686897696a7c876b7e” Client (later request): If-None-Match: "686897696a7c876b7e” Server (later response): 304 Not Modified Learn more at Stormpath.com
76. Maintenance Learn more at Stormpath.com
77. Use HTTP Redirects Create abstraction layer / endpoints when migrating Use well defined custom Media Types Learn more at Stormpath.com
78. IT’S CODING TIME!!! • Let’s build a JAX-RS REST App! • git clone https://github.com/stormpath/todos- jersey.git Learn more at Stormpath.com
79. .com • Free for any application • Eliminate months of development • Automatic security best practices Sign Up Now: Stormpath.com Les Hazlewood | @lhazlewood