REST API Design for JAX-RS And Jersey

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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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REST API Design for JAX-RS And Jersey

  1. 1. REST + JSON APIs with JAX-RS Les Hazlewood CTO, Stormpath stormpath.com
  2. 2. .com • Identity Management and Access Control API • Security for your applications • User security workflows • Security best practices • Developer tools, SDKs, libraries
  3. 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. 4. Why REST? • • • • • • Scalability Generality Independence Latency (Caching) Security Encapsulation Learn more at Stormpath.com
  5. 5. HATEOAS • • • • • • • Hypermedia As The Engine Of Application State Further restriction on REST architectures. Learn more at Stormpath.com
  6. 6. REST Is Easy Learn more at Stormpath.com
  7. 7. REST Is *&@#$! Hard (for providers) Learn more at Stormpath.com
  8. 8. REST can be easy (if you follow some guidelines) Learn more at Stormpath.com
  9. 9. Example Domain: Stormpath • • • • • • Applications Directories Accounts Groups Associations Workflows
  10. 10. Fundamentals Learn more at Stormpath.com
  11. 11. Resources Nouns, not Verbs Coarse Grained, not Fine Grained Architectural style for use-case scalability Learn more at Stormpath.com
  12. 12. What If? /getAccount /createDirectory /updateGroup /verifyAccountEmailAddress Learn more at Stormpath.com
  13. 13. What If? /getAccount /getAllAccounts /searchAccounts /createDirectory /createLdapDirectory /updateGroup /updateGroupName /findGroupsByDirectory /searchGroupsByName /verifyAccountEmailAddress /verifyAccountEmailAddressByToken … Smells like bad RPC. DON‟T DO THIS. Learn more at Stormpath.com
  14. 14. Keep It Simple Learn more at Stormpath.com
  15. 15. The Answer Fundamentally two types of resources: Collection Resource Instance Resource Learn more at Stormpath.com
  16. 16. Collection Resource /applications Learn more at Stormpath.com
  17. 17. Instance Resource /applications/a1b2c3 Learn more at Stormpath.com
  18. 18. Behavior • • • • • GET PUT POST DELETE HEAD Learn more at Stormpath.com
  19. 19. Behavior POST, GET, PUT, DELETE ≠ 1:1 Create, Read, Update, Delete Learn more at Stormpath.com
  20. 20. Behavior As you would expect: GET = Read DELETE = Delete HEAD = Headers, no Body Learn more at Stormpath.com
  21. 21. Behavior Not so obvious: PUT and POST can both be used for Create and Update Learn more at Stormpath.com
  22. 22. PUT for Create Identifier is known by the client: PUT /applications/clientSpecifiedId { … } Learn more at Stormpath.com
  23. 23. PUT for Update Full Replacement PUT /applications/existingId { “name”: “Best App Ever”, “description”: “Awesomeness” } Learn more at Stormpath.com
  24. 24. PUT Idempotent Learn more at Stormpath.com
  25. 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. 26. POST as Update On instance resource POST /applications/a1b2c3 { “name”: “Best App Ever. Srsly.” } Response: 200 OK Learn more at Stormpath.com
  27. 27. POST NOT Idempotent Learn more at Stormpath.com
  28. 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. 29. Design Time! Learn more at Stormpath.com
  30. 30. Base URL Learn more at Stormpath.com
  31. 31. http(s)://api.foo.com vs http://www.foo.com/dev/service/api/rest Learn more at Stormpath.com
  32. 32. http(s)://api.foo.com Rest Client vs Browser Learn more at Stormpath.com
  33. 33. Versioning Learn more at Stormpath.com
  34. 34. URL https://api.stormpath.com/v1 vs. Media-Type application/json+foo;application&v=1 Learn more at Stormpath.com
  35. 35. Resource Format Learn more at Stormpath.com
  36. 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. 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. 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. 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. 40. Response Body Learn more at Stormpath.com
  41. 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. 42. Content Negotiation Learn more at Stormpath.com
  43. 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. 44. Resource Extension /applications/a1b2c3.json /applications/a1b2c3.csv … Conventionally overrides Accept header Learn more at Stormpath.com
  45. 45. Resource References aka „Linking‟ Learn more at Stormpath.com
  46. 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. 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. 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. 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. 50. Reference Expansion (aka Entity Expansion, Link Expansion) Learn more at Stormpath.com
  51. 51. Account and its Directory? Learn more at Stormpath.com
  52. 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. 53. Partial Representations Learn more at Stormpath.com
  54. 54. GET /accounts/x7y8z9?fields=givenName,surname, directory(name) Learn more at Stormpath.com
  55. 55. Pagination Learn more at Stormpath.com
  56. 56. Collection Resource supports query params: • Offset • Limit …/applications?offset=50&limit=25 Learn more at Stormpath.com
  57. 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. 58. Many To Many Learn more at Stormpath.com
  59. 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. 60. GET /groupMemberships/23lk3j2j3 200 OK { “href”: “…/groupMemberships/23lk3j2j3”, “account”: { “href”: “…” }, “group”: { “href”: “…” }, … } Learn more at Stormpath.com
  61. 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. 62. Errors Learn more at Stormpath.com
  63. 63. • As descriptive as possible • As much information as possible • Developers are your customers Learn more at Stormpath.com
  64. 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. 65. Security Learn more at Stormpath.com
  66. 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. 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. 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. 69. API Keys • • • • • • Entropy Password Reset Independence Speed Limited Exposure Traceability Learn more at Stormpath.com
  70. 70. IDs Learn more at Stormpath.com
  71. 71. • IDs should be opaque • Should be globally unique • Avoid sequential numbers (contention, fusking) • Good candidates: UUIDs, „Url64‟ Learn more at Stormpath.com
  72. 72. HTTP Method Overrides Learn more at Stormpath.com
  73. 73. POST /accounts/x7y8z9?_method=DELETE Learn more at Stormpath.com
  74. 74. Caching & Concurrency Control Learn more at Stormpath.com
  75. 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. 76. Maintenance Learn more at Stormpath.com
  77. 77. Use HTTP Redirects Create abstraction layer / endpoints when migrating Use well defined custom Media Types Learn more at Stormpath.com
  78. 78. IT‟S CODING TIME!!! • Let‟s build a JAX-RS REST App! • git clone https://github.com/stormpath/todosjersey.git Learn more at Stormpath.com
  79. 79. .com • Free for any application • Eliminate months of development • Automatic security best practices Sign Up Now: Stormpath.com Les Hazlewood | @lhazlewood

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