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Spring 4 Web ApplicationsRossen Stoyanchev

@rstoya05

About me

• Spring Framework committer• 598 commits / 143,459 ++ / 95,254 --

• Focus on web applications and Spring MVC

• Spring 4 WebSocket messaging lead

Spring MVC 4.1 update

in context of other recent releases

and related projects

Spring MVC Annotations

• @MVC very popular and evolving through feedback

• Started in 2.5 + REST in 3.0

• Many refinements in 3.1 and 3.2

• WebSocket messaging in 4.0

• Continues to evolve in 4.x

@Controller

• The central component stereotype in Spring MVC

• Contains @RequestMapping methods

• Supporting methods:@ModelAttribute/@InitBinder/@ExceptionHandler

@RestController

• Another component stereotype

• Meta-annotated with @Controller + @ResponseBody

• @ResponseBody “inherited” on method level

• No need to add it, assumed by default

@ControllerAdvice

• Yet another component stereotype

• “Global” supporting methods:@ExceptionHandler, @ModelAttribute, @InitBinder

• Auto-detected, just declare it as a bean

• Fine-grained control @ControllerAdvice(basePackageClasses=MyController.class)

Using @ControllerAdvice

• Global exception handling with error details• ResponseEntityExceptionHandler

• Model attribute preparation• like HandlerInterceptor.preHandle but within @MVC

• Common DataBinder initialization

• ResponseBodyAdvice

ResponseBodyAdvice

• Callback for @ResponseBody / ResponseEntity methods

• Just before the response is written (and committed)• you can still modify headers• or the object to be written to the response

• Two implementations already• JsonViewResponseBodyAdvice• AbstractJsonpResponseBodyAdvice

Jackson @JsonView Support

@RestControllerclass UserController {

@RequestMapping("/user")@JsonView(PublicView.class)public User getUser() { return new User("eric", "7!#H2");}

}

interface PublicView {};

class User {

@PublicViewprivate String username;

private String password;

...

}

JSONP Support

Simply declare as Spring-managed bean:

@ControllerAdviceprivate static class JsonpAdviceextends AbstractJsonpResponseBodyAdvice {

public JsonpAdvice() {super("callback");

} }

Name of JSONP query param(s)

java.util.Optional method argument (JDK 1.8)

@RestControllerpublic class TestController { @RequestMapping("/test") public void handle(@RequestParam Optional<LocalDate> date) { StringBuilder sb = new StringBuilder("Date: "); date.ifPresent(s -> sb.append(s.toString())); // ... }

}

ListenableFuture return type

• ListenableFuture• together with AsyncRestTemplate

• Supported on @RequestMapping methods in 4.1• return instead of DeferredResult

• Useful in some cases• business service returns ListenableFuture

@ModelAttribute Method Invocation Order

• Invocation respects inter-dependencies in 4.1

@ModelAttribute("foo")public Object getFoo() {

}

@ModelAttribute("bar")public Object getBar(@ModelAttribute("foo") Object foo) {

}

consumes“foo”

produces“foo”

HttpMessageConverter Additions

• Gson• lighter footprint (vs Jackson); used in Spring Android

• Google Protocol Buffers

• effective inter-service communication data protocol

• Jackson / XML• just add jackson-dataformat-xml to classpath

ResponseEntity builder

public ResponseEntity<String> handle() { String body = "Hello World"; HttpHeaders headers = new HttpHeaders() headers.setLocation(location); return new ResponseEntity<String>(body, headers, HttpStatus.CREATED);}

public ResponseEntity<String> handle() { URI location = ...; return ResponseEntity.created(location).body("Hello World");}

BEFORE

AFTER

RequestEntity builder

HttpHeaders headers = new HttpHeaders();headers.setAccept(MediaType.APPLICATION_JSON);HttpEntity httpEntity = new HttpEntity("Hello World", headers);restTemplate.exchange(uri, HttpMethod.POST, httpEntity, String.class);

restTemplate.exchange(

RequestEntity.post(uri).accept(MediaType.APPLICATION_JSON).body("Hello World"), String.class);

BEFORE

AFTER

Link to @RequestMapping / fromMethodCall

// static import MvcUriComponentsBuilder.*

fromMethodCall(on(MyController.class).getAddress("US")).buildAndExpand(1).toUri();

@RequestMapping("/people/{id}/addresses")public class MyController {

@RequestMapping("/{country}")public HttpEntity getAddress(@PathVariable String country) {}

}

@RequestMapping names

• HandlerMethodMappingNamingStrategy

• A default name assigned to all mappings• e.g. class: MyController, method: getAddress• mapping name: “MC#getAddress”

• Mapping names logged on startup at TRACE

• Override default• @RequestMapping(name=”custom-name”)

Link to @RequestMapping / fromMappingName

// static import MvcUriComponentsBuilder.*

fromMappingName("MC#getAddress").arg(0, "US").buildAndExpand(1);

@RequestMapping("/people/{id}/addresses")public class MyController {

@RequestMapping("/{country}")public HttpEntity getAddress(@PathVariable String country) {}

}

Link to @RequestMapping / in views

• mvcUrl function in Spring JSP tag library• shortcut for MvcUriComponentsBuilder.fromMappingName

<%@ taglib uri="http://www.springframework.org/tags" prefix="s" %>

<a href="${s:mvcUrl('MC#getAddress) .arg(0, 'US').buildAndExpand(1)}">...</a>

Static Resource Handling

• Major Spring Framework 4.1 feature

• Evolve existing ResourceHttpRequestHandler mechanism

• ResourceResolver and ResourceTransformer chains• arbitrary resolution (version in URL path)

• ResourceUrlProvider • prepare “public” resource URL (e.g. insert version)

“Fingerprinting” URLs (content-based version)

boolean useResourceCache = !this.environment.acceptsProfiles("dev"); VersionResourceResolver resolver = new VersionResourceResolver();resolver.addContentVersionStrategy("/**"); registry.addResourceHandler("/**").addResourceLocations(locations) .resourceChain(useResourceCache).addResolver(resolver);

Example URL:“/css/font-awesome.min-7fbe76cdac.css”

Resource Handling: Comprehensive Strategy

• Much more to discuss• optimization of resources (minify, concatenate)• effective HTTP caching• runtime vs build-time approaches

• Separate talk tomorrow (Wednesday) 8:30 AM

Resource Handling in Spring MVC 4.1Brian Clozel, Rossen Stoyanchev

Groovy Markup Templating

• MarkupTemplateEngine in Groovy 2.3 (XML, XHTML, HTML5)

• DRY markup, Groovy DSL (also see blog post)

yieldUnescaped '<!DOCTYPE html>' html(lang:'en') { head { meta('http-equiv':'"Content-Type" content="text/html; charset=utf-8"') title('My page') } body { p('This is an example of HTML contents') } }

Groovy Markup Templating in Spring MVC

• Spring MVC integration

• GroovyMarkupView/ViewResolver/Configurer • similar to FreeMarker and Velocity

New in MVC Java Config: view resolvers

@Configuration@EnableWebMvcpublic class WebConfig extends WebMvcConfigurerAdapter { @Override public void addViewControllers(ViewResolverRegistry registry) { registry.enableContentNegotiation(new MappingJackson2JsonView()); registry.jsp(); } }

New in MVC Namespace: view resolvers

<mvc:view-resolvers>

<mvc:content-negotiation>

<mvc:default-views>

<bean class="org.springframework.web..MappingJackson2JsonView"/>

</mvc:default-views>

</mvc:content-negotiation>

<mvc:jsp />

</mvc:view-resolvers>

MVC Java Config: enhanced view controllers

@Configuration@EnableWebMvcpublic class WebConfig extends WebMvcConfigurerAdapter { @Override public void addViewControllers(ViewControllerRegistry registry) { registry.addRedirectViewController("/old/path", "/new/path"); registry.addStatusController("/path", HttpStatus.NOT_FOUND); } }

MVC Namespace: enhanced view controllers

1234

<mvc:redirect-view-controller path="/old" redirect-url="/new" context-relative="false" status-code="308" keep-query-params="true" /> <mvc:status-controller path="/bad" status-code="404" />

WebSocket Support

• Introduced in 4.0

• Foundational WebSocket API

• Transparent SockJS layer• fall back on HTTP streaming or long polling• wide range of browser versions

• Higher-level STOMP messaging• enables @Controller-style programming model

WebSocket Messaging

@Controller

STOMP

WebSocket API

SockJS

websocket / xhr-streaming / eventsource / xhr / ...

spring-messaging

spring-websocket

Example STOMP Message

SENDdestination:/topic/greetingscontent-type:text/plain

Hello world!

COMMANDheader1:value1header2:value2

Body

STOMPFrame

HTTP Requests with Push Notifications

@Controllerpublic class AccountController { @Autowired private SimpMessagingTemplate template; @RequestMapping(value="/accounts", method=RequestMethod.POST) public void save(@Valid Account account) { // ... // notify connected users this.template.convertAndSend("/topic/accounts", account); }

}

@Controller HTTP and WebSocket Processing

@Controllerpublic class PortfolioController { @MessageMapping("/trade") public void executeTrade(Trade trade) { // ... } @RequestMapping(value="/trades/{id}", method=RequestMethod.GET) public Trade getTrade(Integer id) { // ... }

}

Much More on WebSockets

• WebSocket messaging-style, event-driven architecture• very different from REST/HTTP

• There is a lot to consider and learn

• Separate talk today (Tuesday) at 12:45 am

Deep Dive into Spring WebSocketsSergi Almar

• A tool for getting started quickly

• One-stop shop for Spring application development

• Builds on many spring projects• does all the hard work so you don’t have to

• Focused on the 80% common case• more opinionated and more instantly useful• yet remains flexible

Spring Boot

@RestController

@EnableAutoConfiguration

public class Example {

public static void main(String[] args) throws Exception {

SpringApplication.run(Example.class, args);

}

@RequestMapping("/")

public String home() {

return "Hello World!";

}

}

Spring Boot: Up and Running in Minutes!

$ mvn spring-boot:run

• The @MVC programming model you know

• Optimized to be production ready• auto-config, conventions• embedded servlet container, metrics, logging

• Separate talk today (Tuesday) at 2:30 pm

Spring Boot for the Web TierPhil Webb, Dave Syer

Spring Boot for Web Applications

Spring MVC Test Updates

• Assert JSON responses with JSONAssert library• similar to what XMLUnit does for XML

• AsyncRestTemplate client-side support

• MockMvcBuilder "recipes" via MockMvcConfigurer • added to simplify Spring Security setup

HtmlUnit Extension for Spring MVC Test

• Separate Github project spring-test-htmlunit

• Use HtmlUnit, WebDriver, Geb + your Spring MVC Test setup

• See talk tomorrow (Wednesday) at 4:30 pm

The Quest for the Holy Integration TestKen Krueger, Rob Winch

Q & A

Thank you!