Spring Web Services:SOAP vs. REST

SamBrannenSwi+mindGmbH

SpeakerProfile

•  SeniorSo+wareConsultant–Swi+mindGmbH•  Javadeveloperwith13+years'experience•  SpringFrameworkCoreDeveloper– AuthoroftheSpringTestContextFramework

•  PreviousSpringSourcedmServer™developer•  RegularspeakeratconferencesonSpring,dmServer,Java,OSGi,andtesOng

•  LeadauthorofSpringinaNutshell;chieftechnicalreviewerforSpringRecipes

Agenda

•  WebServicesConcepts•  SpringEventsApplicaOon•  Spring‐WS

•  SpringREST•  Server‐side•  Client‐side•  Q&A

WebServices

Concepts

•  Client/ServerarchitectureovertheWeb– ServerexposesServices– ClientsendsaRequesttotheServer•  foraspecificexposedService•  withaPayloadtobeprocessedbytheService

– ServiceprocessestheRequestandreturnsaResponse

MarshallingandUnmarshalling

•  Marshalling:Objectexternalformat•  Unmarshalling:externalformatObject

•  arequestorresponsecontainsapayload– o+enintheformofanXMLdocument– mayalsobebinary,JSON,etc.

•  applicaOoncodehasitsowndomainmodel– maynotmapdirectlytoformatofpayload

SpringEventsApplica?on

IntroducingSpringEvents

•  SimplePOJOdomainmodel:Event•  TransacOonalservicelayer•  Hibernaterepositorylayer– Withanin‐memoryHSQLdatabase

•  Spring@MVCpresentaOonlayer– RESTful@Controller

•  Spring‐WS@Endpoint

SpringEventsApplicaOon

Demo

SOAPWebServices

WhatisSpring‐WS?

SpringWebServicesaimstofacilitatecontract‐firstSOAPservicedevelopment,allowingforthecreaAonofflexiblewebservicesusingoneofthemanywaystomanipulateXMLpayloads.(Spring‐WSWebsite)

WhatisSOAP?

•  SimpleObjectAccessProtocol– ProtocolforexchanginginformaOonviaWebServices

– UsesXMLasitsmessageformat– TypicallyoverHTTP

•  Structure– Envelope– Header– Body(a.k.a.,payload)– Documentliteral

ContractLast

•  DefineAPIinprogramminglanguage(e.g.,Java)

•  UsetoolstogenerateXSDsandWSDLfromcode

•  Pros–  easy,no‐brainerfordevelopers

•  Cons–  horriblyfragile–  anychangetocodebreakspreviouslypublishedcontract

–  clientsmustbeupdated

ContractFirst

•  DefinepublicAPItoservicesviaXSDschemasfirst– onerequestandresponseperexposedservice– generateWSDLfromXSDsusingconvenOonsforporttypes,etc.•  potenOallyauto‐generated

– generateJavacodefromXSDs(e.g.,JAXB2)– createJavamappingcodemanually– oruseXPath,etc.toparseXMLdirectly

RESTWebServices

WhatisSpringREST?

•  RESTfulWebServicesbuiltontopofSpring@MVC

•  CombinesnicelywithexisOng@MVCcode

•  LowlearningcurvefordevelopersfamiliarwithSpring@MVC

•  SupportsmulOplemarshallingtechnologiessuitableforwebapplicaOons(e.g.,JSON)

•  SpringREST!=JAX‐RS

WhatisREST?

•  REpresentaOonalStateTransfer•  HTTPProtocol– Standard– Ubiquitous– Scalable

•  Stateless•  Focusesonresources– NounsandVerbs

Nouns,Verbs,&Errors

•  Nouns– Resourcesthatyouwanttointeractwith

•  Verbs– Whatyoucandowitharesource•  POST:createnewresource•  GET:getsingleresourceoralistofresources•  PUT:updateresource•  DELETE:deleteresource

•  Errorhandling– StandardHTTPresponsecodes

RESTfulURLs

•  POST– hip://example.com/events

•  GET– hip://example.com/events– hip://example.com/events/1

•  PUT– hip://example.com/events/1

•  DELETE– hip://example.com/events/1

Server‐side

Spring‐WSontheServer

•  Bootstrappedinweb.xmlwithMessageDispatcherServlet

•  <sws:annotaOon‐driven/>enables@Endpointmappings(ala@Controller)

•  @PayloadRootmapshandlermethods

•  @RequestPayloadmapspayloadtomethodparameter

•  @ResponsePayloadmapsreturnvaluetoresponsepayload

GetEventEndpoint(1/2)@Endpointpublic class GetEventEndpoint {

private static final String NAMESPACE_URI = "http://example.com/schemas";

private final EventService eventService;

@Autowired public GetEventEndpoint(EventService eventService) { this.eventService = eventService; }

GetEventEndpoint(2/2)@PayloadRoot(localPart="GetEventRequest", namespace=NAMESPACE_URI)@ResponsePayloadpublic GetEventResponse getEvent( @RequestPayload GetEventRequest request) throws Exception {

Event event = eventService.findById(request.getId().longValue());

return toGetEventResponse(event);}

SpringRESTontheServer

•  RESTWebServiceendpointsare@Controllers– @RequestMapping:mapstohandlermethods– @RequestBody:payloadofrequest– @ResponseBody:payloadofresponse– @ResponseStatus:setHTTPresponsecode– @PathVariableandUriTemplate•  FormappingandcreaOngRESTfulURIs

•  AutomaOcmarshallingofpayloads•  ContentnegoOaOon

EventController(1/4)@RequestMapping("/events")@Controllerpublic class EventController {

protected final EventService eventService;

@Autowired public EventController(EventService eventService) { this.eventService = eventService; }

EventController(2/4)@RequestMapping(method = GET)@ResponseBodypublic List<Event> retrieveAllEvents() { return eventService.findAllEvents();}

@RequestMapping(value = "/{id}", method = GET)@ResponseBodypublic Event retrieveEvent(@PathVariable Long id) { return eventService.findById(id);}

EventController(3/4)@RequestMapping(method = POST)@ResponseStatus(HttpStatus.CREATED)public void createEvent(@RequestBody Event postedEvent, HttpServletRequest request, HttpServletResponse response) {

Event savedEvent = eventService.save(postedEvent);

String newLocation = buildNewLocation(request, savedEvent.getId());

response.setHeader("Location", newLocation);}

EventController(4/4)@RequestMapping(value = "/{id}", method = DELETE)@ResponseStatus(HttpStatus.NO_CONTENT)public void deleteEvent(@PathVariable Long id) { eventService.deleteById(id);}

private String buildNewLocation(HttpServletRequest request, Long id) {

String url = request.getRequestURL() .append("/{id}").toString();

UriTemplate uriTemplate = new UriTemplate(url); return uriTemplate.expand(id).toASCIIString();}

HiddenHipMethodFilter

•  WebbrowserstypicallyonlysupportGETandPOST

•  HiddenHipMethodFilter– providessupportforPUTandDELETErequestsfromwebbrowsers

–  transparentlyconvertsPOSTrequestswithhidden_methodparameter

•  Configuredinweb.xml

•  CanbeusedinconjuncOonwithSpring’sJSPformtaglibrary

URITemplatesinJSPs

•  Usethe<spring>taglibrarytoconstructdynamicURItemplatesinJSPs

•  SimilartotheJSPcoretaglibrarysupportforbuildingURLswithparameters

<spring:urlvar="jsonUrl"value="/rest/events/{id}">

<spring:paramname="id"value="${event.id}"/></spring:url>

Client‐side

WebServiceTemplate

•  InteractwithSOAPWebServicesasaclient•  SupportscallbacksaswellasautomaOcmarshallingandunmarshallingofpayloads– sendAndReceive(…)– marshalSendAndReceive(…)

– etc.

EventsSoapClientTest(1/2)@RunWith(SpringJUnit4ClassRunner.class)@ContextConfigurationpublic class EventsSoapClientTest {

@Autowired private WebServiceTemplate webServiceTemplate;

<oxm:jaxb2-marshaller id="marshaller” contextPath="com.swiftmind.samples.events.web.schema" />

<bean id="webServiceTemplate" class="org.springframework.ws.client.core.WebServiceTemplate” p:marshaller-ref="marshaller" p:unmarshaller-ref="marshaller" />

EventsSoapClientTest(2/2)@Testpublic void getEventRequest() {

String url = "http://localhost:8080/spring/soap";

GetEventRequest request = new GetEventRequest(); request.setId(BigInteger.valueOf(5L));

GetEventResponse response = (GetEventResponse) webServiceTemplate.marshalSendAndReceive(url, request);

assertNotNull(response); assertEquals("Spring I/O in Madrid", response.getEventData().getDescription()); }

RestTemplate

•  InteractwithanyRESTWebServices– notlimitedtoSpringRESTservices

•  SupportsURItemplatesandautomaOcmarshallingandunmarshallingofpayloads– postForLocaOon(…)– postForObject(…)– getForObject(…)– delete(…)– put(…)– etc.

EventsRestClient(1/3)public class EventsRestClient {

private final RestTemplate restTemplate = new RestTemplate(); private String url;

public URI createEvent(String name) { Event event = new Event(); event.setName(name);

return restTemplate.postForLocation(url, event); }

EventsRestClient(2/3)public void deleteEventByLocation(URI location) { restTemplate.delete(location);}

public void deleteEventById(Long id) { String deletionUrl = url + "/{id}";

restTemplate.delete(deletionUrl, id);}

EventsRestClient(3/3)public void retrieveEvent(URI location) { Event event = restTemplate.getForObject(location, Event.class);}

public void retrieveAllEvents() { Event[] events = restTemplate.getForObject(url, Event[].class);}

SpringSOAPWebServices

Demo

SpringRESTWebServices

Demo

FurtherResources

•  SpringFramework–  IncludingSpringREST–  hip://springframework.org

•  Spring‐WS–  hip://staOc.springsource.org/spring‐ws/sites/2.0/

•  GenerateXSDfromXML–  hip://bit.ly/fLI1Bt

Q&A

SamBrannen

sam.brannen[at]swi+mind[dot]com

hip://www.swi+mind.com

hip://twiier.com/sam_brannen

“SpringinaNutshell” hip://oreilly.com/catalog/9780596801946 availablefromO’Reillyin2011