documenting restful apis

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SPRINGONE2GXWASHINGTON, DC

Documenting RESTful APIsAndy Wilkinson

@ankinson

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How RESTful is your API?

2

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REST maturity model

3

Hypermedia

HTTPverbs

Separate Resources

XML-RPC SOAPXML-RPC

Level 0 Level 1 Level 2 Level 3

http://www.crummy.com/writing/speaking/2008-QCon/act3.htmlhttp://martinfowler.com/articles/richardsonMaturityModel.html

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How RESTful do you want it to be?

4

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Making your API easy to document

5

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Consistency

6

HTTP status codesHTTP verbs

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Uniqueness

7

Use distinct relations on your links

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"_links" : { "self" : { "href" : "http://localhost:8080/" }, "notes" : { "href" : "http://localhost:8080/notes" }, "tags" : { "href" : "http://localhost:8080/tags" }

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"_links" : { "self" : { "href" : "http://localhost:8080/tags/3" }, "tagged-notes" : { "href" : "http://localhost:8080/tags/3/notes" }}

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What should you document?

10

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Cross-cutting concerns

11

HTTP status codesHTTP verbs (PUT vs PATCH)

Authentication and authorisationRate limiting

…

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Resources

12

What do the represent?What input do they accept?

What output do the produce?

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Links

13

Where can you go?What will you find when you get there?

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What shouldn’t you document?

14

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URIs

15

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What does it look like whenyou get it wrong?

16

Learning from my mistakes

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And when you get it right?

18

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RESTful API documentation tools

20

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Swagger

21

http://swagger.io

springfox/springfox

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You get a lot for little effort

22

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But…23

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It doesn’t support hypermedia

24

https://github.com/swagger-api/swagger-core/issues/97

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It’s URI centric

25

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Always playing catch up – ResponseEntity

26

https://github.com/springfox/springfox/issues/532

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Always playing catch up – HttpHeaders

27

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The writing experience is unpleasant

28

@RequestMapping(method=RequestMethod.POST, consumes=MediaType.APPLICATION_JSON_VALUE)@ApiOperation(value = "Create a new user", notes = "The name " + "of the user must be at least four characters in length.")

@ApiResponses({@ApiResponse(code=400, message="Bad request"),@ApiResponse(code=201, message="User created")})

@ResponseStatus(HttpStatus.CREATED)public HttpHeaders create(@RequestBody UserInput userInput) {

…}

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It isn’t dry

29

@ApiResponses({@ApiResponse(code=400, message="Bad request"),@ApiResponse(code=201, message="User created")})

@ResponseStatus(HttpStatus.CREATED)public HttpHeaders create(@RequestBody UserInput userInput) { … }

@ExceptionHandler(IllegalArgumentException.class)private ResponseEntity<Void> handleIllegalArgumentException() {

return new ResponseEntity<>(HttpStatus.BAD_REQUEST);}

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It isn’t dry

30

@ApiResponses({@ApiResponse(code=400, message="Bad request"),@ApiResponse(code=201, message="User created")})

@ResponseStatus(HttpStatus.CREATED)public HttpHeaders create(@RequestBody UserInput userInput) { … }

@ExceptionHandler(IllegalArgumentException.class)private ResponseEntity<Void> handleIllegalArgumentException() {

return new ResponseEntity<>(HttpStatus.BAD_REQUEST);}

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It isn’t dry

31

@ApiResponses({@ApiResponse(code=400, message="Bad request"),@ApiResponse(code=201, message="User created")})

@ResponseStatus(HttpStatus.CREATED)public HttpHeaders create(@RequestBody UserInput userInput) { … }

@ExceptionHandler(IllegalArgumentException.class)private ResponseEntity<Void> handleIllegalArgumentException() {

return new ResponseEntity<>(HttpStatus.BAD_REQUEST);}

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Swagger2Markup

32

Swagger2Markup/swagger2markup

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HAL and HAL Browser

33

http://stateless.co/hal_specification.html

mikekelly/hal-browser

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HAL Browser demo

34

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Spring REST Docs

35

spring-projects/spring-restdocs

http://projects.spring.io/spring-restdocs

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Write as much as possible in a format that’s designed for writing

36

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Don’t use the implementation to provide the documentation

37

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Provide some guarantees that the documentation is accurate

TDD – Test-Driven Documentation

38

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AsciidoctorSpring MVC TestMaven or Gradle

39

spring-projects/spring-restdocs

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@Testpublic void index() throws Exception { this.mockMvc.perform(get("/"))

.andExpect(status().isOk()) .andExpect(jsonPath("_links.notes",

is(notNullValue()))) .andExpect(jsonPath("_links.tags",

is(notNullValue()))) .andDo(document("index"));

}5

4

3

2

1

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[source,bash]----$ curl 'http://localhost:8080/' -i----

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[source,http]----HTTP/1.1 200 OKContent-Type: application/hal+json

{ "_links" : { "tags" : { "href" : "http://localhost:8080/tags" }, "notes" : { "href" : "http://localhost:8080/notes" }}

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this.mockMvc.perform(get("/")) .andExpect(status().isOk()) .andDo(document("index", links( linkWithRel("notes").description( "The <<resources-notes, Notes resource>>"), linkWithRel("tags").description( "The <<resources-tags, Tags resource>>") ), responseFields( fieldWithPath("_links").description( "<<resources-index-links,Links>> to other resources") )));

4

3

2

1

5

6

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|===| Relation | Description

| notes| The <<resources-notes,Notes resource>>

| tags| The <<resources-tags,Tags resource>>|===

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|===|Path|Type|Description

|_links|Object|<<resources-index-links,Links>> to other resources

|===

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Spring REST Docs demo

50

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Thank you

51

@ankinson

wilkinsona

awilkinson@pivotal.io