Spring 4 Web App

1. Spring 4 Web Applications Rossen Stoyanchev Pivotal Inc

2. About the speaker ● Spring Framework committer ● Spring MVC ● Spring WebSocket and Messaging

3. Spring MVC ● Since 2003 (circa JDK 1.4) ● Before Java annotations, REST, SPAs, ... ● Continued success, evolution ● Most popular status today

4. Programming Model Evolution ● @Controller ………...………... 2.5 (2007) ● REST …………………………….. 3.0 (2009) ● Async requests ……………….. 3.2 (2012) ● WebSocket messaging …….. 4.0 (2013)

5. ● Simple, clean design at the core ● Friendly to extension ● Embraces HTTP and REST ● Community requests Keys to Success

6. Always Evolving ● One of most actively developed parts of Spring Framework ● Continuous flow of ideas and requests from the community ● Improvements, new features, even modules with each new version

7. @MVC @Controller @InitBinder @ModelAttribute @RequestMapping @ExceptionHandler

8. @RestController @RestController public class MyController { @RequestMapping @ResponseBody public Foo handle() { … } @RequestMapping @ResponseBody public Bar handle() { … } }

9. Beyond Class Hierarchy @ControllerAdvice @InitBinder @ModelAttribute @ExceptionHandler

10. Selectors @ControllerAdvice => “Apply to every @Controller” @ControllerAdvice(basePackages = "org.app.module") @ControllerAdvice(annotations = RestController.class) @ControllerAdvice(assignableTypes = {BaseController1.class, BaseController2.class})

11. ResponseEntityExceptionHandler ● Base class for use with @ControllerAdvice ● Handle Spring MVC exceptions ● REST API error details in response body

12. ResponseBodyAdvice ● Interface for use with @ControllerAdvice ● Customize response before @ResponseBody & ResponseEntity are written ● Built-in usages ○ @JsonView on @RequestMapping methods ○ JSONP

13. Further Jackson Support ● Use Jackson for both JSON and XML ● ObjectMapper builder ● Highly recommended read: https://spring.io/blog/2014/12/02/ latest-jackson-integration- improvements-in-spring

14. @RequestMapping methods ● java.util.Optional (JDK 1.8) support ● ListenableFuture return value ● ResponseEntity/RequestEntity builders ● Links to @MVC methods ● @ModelAttribute method ordering

15. ResponseEntityBuilder String body = "Hello"; HttpHeaders hdrs = new HttpHeaders() headers.setLocation(location); new ResponseEntity<String>(body, hdrs, CREATED); vs ResponseEntity.created(location).body("Hello");

16. RequestEntityBuilder HttpHeaders headers = new HttpHeaders(); headers.setAccept(MediaType.APPLICATION_JSON); new HttpEntity("Hello", headers); vs RequestEntity.post(uri) .accept(MediaType.APPLICATION_JSON) .body("Hello");

17. Link to @RequestMapping ● Simulate controller method invocation fromMethodCall(on(MyController.class).getAddress("US")) .buildAndExpand(1).toUri(); ● Uses proxy, similar to testing w/ mocks ● See section on Building URIs

18. How to link from views? ● Refer to @RequestMapping by name ● Default name assigned to every mapping ○ or use @RequestMapping(name=”..”) ● See subsection in Building URIs

19. @ModelAttribute Ordering <- Call this 1st @ModelAttribute("foo") public Object getFoo() { } @ModelAttribute("bar") public Object getBar(@ModelAttribute("foo") Object foo) { } Uses “foo” Creates “foo”

20. Static Resources ● Key topic for web applications today ○ Optimize .. minify, concatenate ○ Transform .. sass, less ○ HTTP caching .. versioned URLs ○ CDN ○ Prod vs dev

21. Static Resources in 4.1 ● Build on existing ResourceHttpRequestHandler ● Add abstractions to resolve and transform resources in a chain ● Prepare “public” resource URL

22. URL “Fingerprinting” ● HTTP “cache busting” ● Version URL with content-based hash ● Add aggressive cache headers (e.g. +1 year) Example URL: “/css/font-awesome.min-7fbe76cdac.css”

23. Static Resources Continued See Resource Handling talk on Youtube, browse the slides, or check the source code.

24. Groovy Markup Templating ● DRY markup based on Groovy 2.3 ● Like HAML in Ruby on Rails yieldUnescaped '<!DOCTYPE html>' html(lang:'en') { head { title('My page') } body { p('This is an example of HTML contents') } }

25. MVC Config ● We now have ViewResolver registry ● ViewController can do more ○ redirects, 404s, etc. ● Patch matching by popular demand ○ suffix patterns, trailing slashes, etc.

26. Servlet 3 Async Requests ● Since v3.2 ○ Long polling, HTTP streaming ● Server can push events to client ○ chat, tweet stream ● Relatively simple, close to what we know ● Not easy for more advanced uses ○ games, finance, collaboration

27. Web Messaging ● WebSocket protocol ○ bi-directional messaging between client & server ● SockJS fallback ○ WebSocket emulation (IE < 10, proxy issues, etc.) ● STOMP ○ Simple messaging sub-protocol ○ Like HTTP over TCP

28. Why not just WebSocket? ● Too low level ● Practically a TCP socket ● Just like HTTP enables RESTful architecture, STOMP enables messaging ● In the absence of a protocol, a custom protocol will have to be used

29. Example STOMP Frame SEND destination:/app/greetings content-type:text/plain Hello world!

30. Handle a Message @Controller public class PortfolioController { @MessageMapping("/greetings") public void add(String payload) { … } }

31. Messaging + REST @Controller public class PortfolioController { @MessageMapping("/greetings") public void add(String payload) { … } @RequestMapping("/greetings", method=GET) public String get() { … } }

32. SockJS ● Exact same WebSocket API ● Different transports underneath ○ long polling, HTTP streaming ● Wide range of browsers and versions ● WebSocket alone not practically usable without fallback options today

33. WebSocket Continued See presentation: https://github.com/rstoyanchev/ springx2013-websocket There is also a video available.

34. Spring Boot ● You are an expert but how long would it take you to start a new web application? ● Lot of choices to be made ● Boot makes reasonable default choices ● So you can be up and running in minutes

35. Spring Boot Web App @RestController @EnableAutoConfiguration public class Example { public static void main(String[] args) { SpringApplication.run(Example.class, args); } @RequestMapping("/") public String home() { return "Hello World!"; } }

36. REST API Docs ● Good REST API documentation can not be fully generated ● Every good API guide has some stories and use cases with example usage ● Yet manually writing it all is too much

37. Spring REST Docs ● What if you could write real tests that demonstrate your REST API? ● Using Spring MVC Test... ● Then insert the code w/ actual output in your Asciidoctor documentation

38. Spring REST Docs Continued Check out this webinar by Andy Wilkinson

39. Server-Sent Events v4.2 @RequestMapping public ResponseEntity<SseEmitter> handle() { SseEmitter emitter = new SseEmitter(); // ... return emitter; } // Later from another thread emitter.send(event().name("foo").data(foo)); … emitter.complete();

40. Server-Sent Events v4.2 @RequestMapping public ResponseEntity<SseEmitter> handle() { if ( … ) { return ResponseEntity.status(204).body(null); } else { // … ResponseEntity.ok(sseEmitter); } } SPR-12672

41. HTTP Caching v4.2 ● Comprehensive update according to the most recent HTTP 1.1. spec updates ● Central and per-request support for all Cache-Control directives ● A deep eTag strategy SPR-11792

42. CORS v4.2 ● Built-in support within Spring MVC ● Both central and fine-grained ● @CrossOrigin ● CorsConfigurationSource SPR-9278

43. Custom @RequestMapping v4.2 @RequestMapping( method = RequestMethod.POST, produces = MediaType.APPLICATION_JSON_VALUE consumes = MediaType.APPLICATION_JSON_VALUE) public @interface PostJson { String value() default ""; } @PostJson("/input") public Output myMethod(Input input) { } SPR-12296

44. JavaScript Templating v4.2 ● Server-side JavaScript templates ● See very long SPR-12266 ● Current plan is to plug Nashorn (JDK 1.8) behind the ViewResolver/View contracts ● Much like we did for Groovy in 4.1

45. STOMP Client v4.2 ● There aren’t any good Java clients ● So we’ve decided to write one ● Good for testing at least ● Like we added SockJS Java client in 4.1 SPR-11588

46. Topical Guides ● Part of effort to overhaul Spring Framework reference documentation ● Separate “conceptual” information from pure reference ● Example guides ○ “What is Spring”, “Intro to Spring Config”, etc. ● Track topical-guides repo

47. Questions http://twitter.com/rstoya05 http://pivotal.io

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Spring 4 Web App

Rossen Stoyanchev

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