Introduction to WebMvc.fn

Confidential │ ©2020 VMware, Inc.
Introduction to
WebMvc.fn
Functional Servlet Endpoints
Arjen Poutsma (@poutsma)
Sr. Staff Engineer at VMware
3rd September 2020

Agenda
2
Handler Functions
Router Functions
Filter Functions
Final Comparison

Confidential │ ©2020 VMware, Inc. 3
WebMvc.fn was introduced
in Spring 5.2 and is fully
compatible with Spring Boot

Handler Functions
Map from ServerRequest to ServerResponse
4

Handler Functions
@Controller
class PersonController {
PersonRepository repository;
ResponseEntity<Person> getPerson(@PathVariable String id) {
Person person = repository.findById(id);
return ResponseEntity.ok()
.contentType(APPLICATION_JSON)
.body(person);
}
ResponseEntity<List<Person>> getPeople() {
List<Person> people = repository.findAll();
.body(people);
}
}
Web MVC

Handler Functions
@Controller
class PersonHandler {
ServerResponse getPerson(ServerRequest request) {
String id = request.pathVariable("id");
return ServerResponse.ok()
.body(person);
}
ServerResponse getPeople(ServerRequest request) {
.body(people);
}
}
WebMvc.fn

Web MVC WebMvc.fn
6
Handler Function Comparison
@Controller
.body(person);
}
.body(people);
}
}
@Controller
String id = request.pathVariable("id");
.body(person);
}
.body(people);
}
}

Handler Functions map from
ServerRequest to ServerResponse
• both are immutable
• create response with builder

Router Functions
Map from ServerRequest to HandlerFunction
8

Router Functions
@Controller
@RequestMapping("/people")
@RequestMapping(value = "/{id}", method = GET)
...
}
@RequestMapping(method = GET)
...
}
}
Web MVC

Router Functions
@Controller
...
}
...
}
@Bean
static RouterFunction router(PersonHandler handler) {
return route()
.GET("/people/{id}", handler::getPerson)
.GET(“/people", handler::getPeople)
.build();
}
}
WebMvc.fn

Router Functions
@Controller
...
}
...
}
@Bean
return route()
.path(“/people", builder -> builder
.GET("/{id}", handler::getPerson)
.GET("/", handler::getPeople));
.build();
}
}
WebMvc.fn

Web MVC WebMvc.fn
10
Router Function Comparison
@Controller
...
}
...
}
@Bean
return route()
.path(“/people", builder -> builder
.GET("/", handler::getPeople));
.build();
}
}
@Controller
@RequestMapping(“/people")
@RequestMapping(value = "/{id}", method = GET)
...
}
@RequestMapping(method = GET)
...
}
}

Router Functions created using builder
• GET, POST, PUT, etc.
• resources
• nesting
• more powerful abstraction underneath:
RequestPredicate

Request Predicates
Evaluate on a ServerRequest
12

Request Predicates
RequestPredicate get = RequestPredicates.method(HttpMethod.GET);
RequestPredicate people = RequestPredicates.path("/people");
RequestPredicate getPeople = get.and(people); // or RequestPredicates.GET("/people")
RequestPredicate acceptJson = RequestPredicates.accept(APPLICATION_JSON);
RequestPredicate extensionJson = RequestPredicates.pathExtension("json");
RequestPredicate paramTypeJson = RequestPredicates.param("type", "json");
RequestPredicate json = acceptJson.or(extensionJson).or(paramTypeJson);

Request Predicates
@Controller
...
ServerResponse createPerson(ServerRequest request) {
Person person = request.body(Person.class);
repository.savePerson(person);
.build();
}
@Bean
return route()
.path("/people", b -> b
.GET("/{id}", accept(APPLICATION_JSON), handler::getPerson)
.GET("/", accept(APPLICATION_JSON), handler::getPeople)
.POST("/", contentType(APPLICATION_JSON), handler::createPerson))
.build();
}
}

Request Predicates
@Controller
...
ServerResponse createPerson(ServerRequest request) {
Person person = request.body(Person.class);
this.repository.savePerson(person);
.build();
}
@Bean
static RouterFunction<ServerResponse> routerFunction(PersonHandler handler) {
return route()
.path(“/people", b -> b
.nest(accept(APPLICATION_JSON), b1 -> b1
.GET("/", handler::getPeople)
)
.build();
}
}

Web MVC WebMvc.fn
15
Request Predicates Comparison
@Controller
@RequestMapping(“/people”)
@RequestMapping(value = "/{id}",
method = GET,
produces = APPLICATION_JSON_VALUE)
...
}
@RequestMapping(method = GET,
produces = APPLICATION_JSON_VALUE)
ResponseEntity<List<Person>> showPeople() {
...
}
@RequestMapping(method = POST,
consumes = APPLICATION_JSON_VALUE)
void createPerson(RequestEntity<Person> person) {
...
}
}
@Controller
...
@Bean
return route()
.GET("/{id}", accept(APPLICATION_JSON), handler::getP
.GET("/", accept(APPLICATION_JSON), handler::getPeopl
.POST("/", contentType(APPLICATION_JSON), handler::cr
.build();
}
}

Web MVC WebMvc.fn
16
@Controller
...
@Bean
static RouterFunction<ServerResponse> routerFunction(Person
return route()
.path("/person", b -> b
)
.POST("/", contentType(APPLICATION_JSON), handler::cr
.build();
}
}
?

Handler Filter Functions
Maps ServerRequest and HandlerFunction
to ServerResponse
17

Maps ServerRequest and HandlerFunction to ServerResponse
@Controller
...
@ExceptionHandler(NotFoundException.class)
ResponseEntity notFound() {
return ResponseEntity.notFound().build()
}
}
Web MVC

@Controller
...
ServerResponse notFound(Throwable throwable, ServerRequest request) {
return ServerResponse.notFound().build();
}
@Bean
return route()
)
.onError(NotFoundException.class, handler::notFound)
.build();
}
}
WebMvc.fn

@Controller
...
}
@Bean
return route()
)
.build();
}
}
WebMvc.fn

Web MVC WebMvc.fn
19
Handler Filter Function Comparison
@Controller
...
@ExceptionHandler(NotFoundException.class)
ResponseEntity notFound() {
return ResponseEntity.notFound().build()
}
}
@Controller
...
}
@Bean
return route()
.path("/person", b -> b
)
.build();
}
}

Final Comparison
20

• Functions
• Code
• Rigid handler methods
(ServerRequest→ServerResponse)
• Flexible routing
• Annotations
• Meta-data
• Flexible handler methods
(parameters & return type)
• Limited routing
Web MVC WebMvc.fn
21

Thank You

Introduction to WebMvc.fn

More Related Content

What's hot (20)

Similar to Introduction to WebMvc.fn (9)

More from VMware Tanzu (20)

Recently uploaded (20)

Introduction to WebMvc.fn