MTAT Enterprise System Integration

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1 MTAT Enterprise System Integration Lecture 7: Hypermedia REST Luciano García-Bañuelos University of Tartu

Codes 1xx - Metadata 2xx Everything s fine 3xx Redirec5on 4xx Client did

2 Richardson s Maturity Level 2 Also known as CRUD services Mul5ple URIs, mul5ple HTTP verbs, and HTTP Status Codes HTTP verbs GET, POST, PUT, DELETE HTTP Status Codes 1xx - Metadata 2xx Everything s fine 3xx Redirec5on 4xx Client did something wrong 5xx Server did a bad thing HYPERMEDIA REST LUCIANO GARCÍA- BAÑUELOS 1

3 Hypermedia within our application? HATEOAS: Hypermedia as the engine of applica5on state Roy Fielding s view: The simultaneous presenta0on of informa0on and controls such that the informa0on becomes the affordance through which the user obtains choices and selects ac0ons. A simpler wording: Include links into the resource representa0on. Let the user (human or program) con0nue the execu0on by following one of those links. HYPERMEDIA REST LUCIANO GARCÍA- BAÑUELOS 2

4 Example: PO creation (BuildIt) POST /pos h[p://ren5t.com/rest BuildIt <purchaseorder>! <start> </start>! <end> </end>! <plant>! <name>excavator</name>! <plant>! </purchaseorder>! RentIt HTTP/1.1 Loca5on: 201 Created /pos/1253 HYPERMEDIA REST LUCIANO GARCÍA- BAÑUELOS 3

5 Example: RentIt s view GET /pos/1253 h[p://ren5t.com/rest HTTP/ Ok RentIt <purchaseorder>! <start> </start>! <end> </end>! <cost> </cost>! <plant>! <sku>exc1253ab98</sku>! <name>excavator</name>! <plant>! <links>! <link rel="accept" href="/pos/1253/accept" method="post"/>! <link rel="reject" href="/pos/1253/accept" method="delete"/>! </links>! </purchaseorder>! HYPERMEDIA REST LUCIANO GARCÍA- BAÑUELOS 4

6 Our example application PurchaseOrderRESTController createpo() acceptpo() rejectpo() resubmitpo() requestpoupdate() acceptpoupdate() rejectpoupdate() POUpdateReqResource enddate PurchaseOrderResource startdate: Date enddate: Date total: Double PlantResource name: String description: String price: Double Plant <<Enumeration>> POStatus PENDING_ACCEPTANCE OPEN PENDING_UPDATE_ACCEPTANCE CLOSED REJECTED <<Enumeration>> URStatus OPEN ACCEPTED REJECTED Customer PurchaseOrder startdate: Date enddate: Date total: Double status: POStatus name: String description: String price: Double updates POUpdateRequest enddate: Date status: URStatus HYPERMEDIA REST LUCIANO GARCÍA- BAÑUELOS 5

7 Our example application PurchaseOrderRESTController createpo() acceptpo() rejectpo() resubmitpo() requestpoupdate() acceptpoupdate() rejectpoupdate() POUpdateReqResource enddate PurchaseOrderResource startdate: Date enddate: Date total: Double PlantResource name: String description: String price: Double PurchaseOrderService createpo() acceptpo() rejectpo() resubmitpo() requestpoupdate() acceptpoupdate() rejectpoupdate() HYPERMEDIA REST LUCIANO GARCÍA- BAÑUELOS 6

8 Resource life cycle: Purchase order PurchaseOrderService createpo() acceptpo() rejectpo() resubmitpo() requestpoupdate() acceptpoupdate() rejectpoupdate() createpo rejectpo pending confirmation rejected updatepo acceptpo acceptpoupdate open closepo closed rejectpoupdate requestpoupdate pending update HYPERMEDIA REST LUCIANO GARCÍA- BAÑUELOS 7

9 Hypermedia API rejectpo rejected createpo pending confirmation acceptpo open Verb URI template Rela?on Current state New state Comments POST /pos createpo Pending confirma5on POST /pos/{po.id/accept acceptpo Pending confirma5on DELETE /pos/{po.id/accept rejectpo Pending confirma5on Open Rejected Submit par5al representa5on Use empty body HYPERMEDIA REST LUCIANO GARCÍA- BAÑUELOS 8

10 Full Purchase Order API Method URI template Rela?on Current state New state Comments POST /pos createpo Pending confirma5on POST /pos/{po.id/accept acceptpo Pending confirma5on DELETE /pos/{po.id/accept rejectpo Pending confirma5on Open Rejected UPDATE /pos/{po.id updatepo Rejected Pending confirma5on DELETE /pos/{po.id closepo Open Closed POST /pos/{po.id/updates requestpoupdate Open Pending update POST DELETE /pos/{po.id/updates/ {up.id/accept /pos/{po.id/updates/ {up.id/accept acceptpoupdate rejectpoupdate Pending update Pending update Open Open Submit par5al representa5on Use empty body Submit new full representa5on Submit new end date Use empty body HYPERMEDIA REST LUCIANO GARCÍA- BAÑUELOS 9

11 Annotated State model DELETE /pos/{po.id/accept rejectpo rejected POST /pos createpo pending confirmation UPDATE /pos/{po.id updatepo POST /pos/{po.id/updates/{up.id/accept acceptpoupdate open POST /pos/{po.id/accept acceptpo DELETE /pos/{po.id closepo closed DELETE /pos/{po.id/updates/{up.id/accept rejectpoupdate POST /pos/{po.id/updates requestpoupdate pending update HYPERMEDIA REST LUCIANO GARCÍA- BAÑUELOS 10

Annotated State model Events produced by BuildIt DELETE /pos/{po.id/accept rejectpo rejected POST /pos createpo pending confirmation UPDATE /pos/{po.id updatepo POST /pos/{po.id/updates/{up.

12 Annotated State model Events produced by BuildIt DELETE /pos/{po.id/accept rejectpo rejected POST /pos createpo pending confirmation UPDATE /pos/{po.id updatepo POST /pos/{po.id/updates/{up.id/accept acceptpoupdate open POST /pos/{po.id/accept acceptpo DELETE /pos/{po.id closepo closed DELETE /pos/{po.id/updates/{up.id/accept rejectpoupdate POST /pos/{po.id/updates requestpoupdate pending update HYPERMEDIA REST LUCIANO GARCÍA- BAÑUELOS 11

13 A look at the business logic layer REST LUCIANO GARCÍA- BAÑUELOS 12

Purchase Order: Service Class @Service public class PurchaseOrderService { @Autowired PlantRepository plantrep; public void createpo(purchaseorder po) throws PlantUnavailableException { DateTime

14 Purchase Order: Service public class PurchaseOrderService PlantRepository plantrep; public void createpo(purchaseorder po) throws PlantUnavailableException { DateTime startdate = new DateTime(po.getStartDate()); DateTime enddate = new DateTime(po.getEndDate()); int days = Days.daysBetween(startDate, enddate).getdays(); String plname = po.getplant().getname(); List<Plant> plants = plantrep.findbynameandavailability(plname, startdate, enddate); if (plants.isempty()) throw new PlantUnavailableException("The requested plant is not available"); po.settotal(days * plants.get(0).getprice()); po.setplant(plants.get(0)); po.persist(); Package: ~.services HYPERMEDIA REST LUCIANO GARCÍA- BAÑUELOS 13

15 Implementing the Hypermedia API REST LUCIANO GARCÍA- BAÑUELOS 14

Changes on resource classes @Entity @Data public class Plant { private String name;

models In this case, we will use the library spring- hateoas.

our previous version. Note that we will use JSON as the representa5on format.

name; integra5on.dto Maven dependency Group id: org.springframework.

16 Changes on public class Plant { private String name; private String description; private Double price; Package: ~.models In this case, we will use the library spring- hateoas. However, the classes required and their implementa5on are quite similar to those in our previous version. Note that we will use JSON as the public class PlantResource extends ResourceSupport { private String name; private String description; private Double price; Package: ~.integra5on.dto Maven dependency Group id: org.springframework.hateoas Ar5fact id: spring- hateoas Version: RELEASE REST LUCIANO GARCÍA- BAÑUELOS 15

Resource assembler public class PlantResourceAssembler extends ResourceAssemblerSupport<Plant, PlantResource> { public PlantResourceAssembler() { super(plantrestcontroller.class, PlantResource.

17 Resource assembler public class PlantResourceAssembler extends ResourceAssemblerSupport<Plant, PlantResource> { public PlantResourceAssembler() { super(plantrestcontroller.class, public PlantResource toresource(plant plant) { PlantResource resource; resource = createresourcewithid(plant.getid(), plant); resource.setname(plant.getname()); resource.setdescription(plant.getdescription()); resource.setprice(plant.getprice()); return resource; HYPERMEDIA REST LUCIANO GARCÍA- BAÑUELOS 16

REST service façade (creation) @RestController @RequestMapping("/rest/pos") public class PurchaseOrderRESTController { @Autowired PurchaseOrderService service; @RequestMapping(method =

pending_confirmation); service.createpo(po); HttpHeaders headers = new HttpHeaders(); URI uri = linkto(purchaseorderrestcontroller.class).slash(po.getid()).touri(); headers.

18 REST service public class PurchaseOrderRESTController PurchaseOrderService = RequestMethod.POST, value = "") public ResponseEntity<PurchaseOrderResource> createpo(@requestbody PurchaseOrder po) throws PlantUnavailableException { po.setstatus(postatus.pending_confirmation); service.createpo(po); HttpHeaders headers = new HttpHeaders(); URI uri = linkto(purchaseorderrestcontroller.class).slash(po.getid()).touri(); headers.setlocation(uri); PurchaseOrderResource pors = assembler.toresource(po); ResponseEntity<PurchaseOrderResource> response; response = new ResponseEntity<>(poRs, headers, HttpStatus.CREATED); return response; HYPERMEDIA REST LUCIANO GARCÍA- BAÑUELOS 17

REST service façade (retrieval) @Controller @RequestMapping("/rest/pos") public class PurchaseOrderRESTController { @RequestMapping(method = RequestMethod.

19 REST service public class PurchaseOrderRESTController = RequestMethod.GET, value = "{id") public ResponseEntity<PurchaseOrderResource> getpo(@pathvariable Long id) { PurchaseOrder po = PurchaseOrder.findPurchaseOrder(id); PurchaseOrderResourceAssembler assembler = new PurchaseOrderResourceAssembler(); PurchaseOrderResource resource = assembler.toresource(po); switch (po.getstatus()) { case PENDING_CONFIRMATION: Method _acceptpo = PurchaseOrderRESTController.class.getMethod("acceptPO", Long.class); String acceptlink = linkto(_acceptpo, po.getid()).touri().tostring(); resource.add(new ExtendedLink(acceptLink, "acceptpo", "POST")); Method _rejectpo = PurchaseOrderRESTController.class.getMethod("rejectPO", Long.class); String rejectlink = linkto(_rejectpo, po.getid()).touri().tostring(); resource.add(new ExtendedLink(rejectLink, "rejectpo", "DELETE")); break; default: break; ResponseEntity<PurchaseOrderResource> response; response = new ResponseEntity<>(resource, HttpStatus.OK); return response; HYPERMEDIA REST LUCIANO GARCÍA- BAÑUELOS 18

20 Exception handling HYPERMEDIA REST LUCIANO GARCÍA- BAÑUELOS 19

21 Example GET /pos/1253 h[p://ren5t.com/rest HTTP/ Ok <purchaseorder>...</purchaseorder>! HTTP/ Not found RentIt HTTP/ Unauthorized HTTP/ Internal Server Error HYPERMEDIA REST LUCIANO GARCÍA- BAÑUELOS 20

22 Exception handling & HTTP status codes 400 Bad Request The client has PUT or POST a resource representa5on that is in the right format, but contains invalid informa5on 401 Unauthorized Proper creden5als to operate on a resource were not provided Response WWW-Authenticate header contains the type of authen5ca5on the server expects Basic, digest, WSSE, etc. 403 Forbidden The client request is OK, but the server doesn t want to process it (e.g., Restricted by IP address) HYPERMEDIA REST LUCIANO GARCÍA- BAÑUELOS 21

23 Exception handling & HTTP status codes 404 Not Found The standard catch- all response 405 Method Not Allowed The resource does not support a given method. Use Allow header to list the verbs the resource understands (e.g., Allow: GET, POST, PUT) 409 Conflict Tried to change the state of the resource to something the server will not allow HYPERMEDIA REST LUCIANO GARCÍA- BAÑUELOS 22

24 Exception handling & HTTP status codes 406 Not Acceptable The server cannot reply with the representa5on requested by the client HTTP header Accept 415 Unsupported Media Type The server cannot consume the resource format used by the client HTTP header Content-type HYPERMEDIA REST LUCIANO GARCÍA- BAÑUELOS 23

Exception handling within our REST controller @RestController @RequestMapping("/rest/pos") public class PurchaseOrderRESTController {

class) public ResponseEntity<String> handlebadrequest(exception ex) { return new ResponseEntity<>(ex.getMessage(), HttpStatus.

25 Exception handling within our public class PurchaseOrderRESTController InvalidHirePeriodException.class) public ResponseEntity<String> handlebadrequest(exception ex) { return new ResponseEntity<>(ex.getMessage(), public ResponseEntity<String> handlenotfound(exception ex) { return new ResponseEntity<>(ex.getMessage(), HttpStatus.NOT_FOUND); HYPERMEDIA REST LUCIANO GARCÍA- BAÑUELOS 24

MTAT Enterprise System Integration

MTAT Enterprise System Integration MTAT.03.229 Enterprise System Integration Lecture 6: Hypermedia REST Luciano García- Bañuelos University of Tartu Richardson s Maturity Level 2 Also known as CRUD services Multiple URIs, multiple HTTP