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REST Assured Hypermedia APIs with Spring Oliver Gierke

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Oliver Gierke SpringSource Engineer Spring Data ogierke@vmware.com olivergierke www.olivergierke.de

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Background

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REST

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REST Resources URIs Uniform Interface Representations Hypermedia

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Hypermedia

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Hypermedia Links in representations State navigations discoverable

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"HATEOAS - the word, there's no pronounciation for. (Ben Hale, SpringOne2GX 2012)

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REST in practice

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No content

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RESTBucks

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RESTBucks Starbucks (like) coffee ordering Order / Payment

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No content

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payment expected 1

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payment expected 1 2

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payment expected cancelled 1 2 3

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payment expected preparing cancelled 1 2 3 4

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payment expected preparing cancelled ready 1 2 3 4 5

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payment expected preparing cancelled ready completed 1 2 3 4 5 6

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Method URI Action Step POST /orders Create new order 1 POST/PATCH /orders/4711 Update the order (only if "payment expected") 2 DELETE /orders/4711 Cancel order (only if "payment expected") 3 PUT /orders/4711/payment Pay order 4 Barista preparing the order Barista preparing the order Barista preparing the order Barista preparing the order GET /orders/4711 Poll order state 5 GET /orders/4711/receipt Access receipt DELETE /orders/4711/receipt Conclude the order process 6

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Challenges

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Challenges How to avoid hard coding URIs?

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Use link relations

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orders Returns all orders available in the system order Returns a single order self The uri value can be used to GET the latest resource representation of the order. cancel This is the URI to be used to DELETE the order resource should the consumer wish to cancel the order. update Consumers can change the order using a POST to transfer a representation to the linked resource. payment The linked resource allows the consumer to begin paying for an order. Initiating payment involves PUTting an appropriate resource representation to the specified URI. receipt The URI to access the receipt using GET and conclude the order by taking the receipt (use DELETE).

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orders Returns all orders available in the system order Returns a single order self The uri value can be used to GET the latest resource representation of the order. cancel This is the URI to be used to DELETE the order resource should the consumer wish to cancel the order. update Consumers can change the order using a POST to transfer a representation to the linked resource. payment The linked resource allows the consumer to begin paying for an order. Initiating payment involves PUTting an appropriate resource representation to the specified URI. receipt The URI to access the receipt using GET and conclude the order by taking the receipt (use DELETE).

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Method URI Action Step POST /orders Create new order 1 POST/PATCH /orders/4711 Update the order (only if "payment expected") 2 DELETE /orders/4711 Cancel order (only if "payment expected") 3 PUT /orders/4711/payment Pay order 4 Barista preparing the order Barista preparing the order Barista preparing the order Barista preparing the order GET /orders/4711 Poll order state 5 GET /orders/4711/receipt Access receipt DELETE /orders/4711/receipt Conclude the order process 6

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Method Relation type Action Step POST orders Create new order 1 POST/PATCH order Update the order (only if "payment expected") 2 DELETE order Cancel order (only if "payment expected") 3 PUT payment Pay order 4 Barista preparing the order Barista preparing the order Barista preparing the order Barista preparing the order GET order Poll order state 5 GET receipt Access receipt DELETE receipt Conclude the order process 6

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Challenges How to implement: "only if payment expected"?

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Process modeling

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Root resource The only URI known GET /

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{ links : [ { rel : "orders", href : "…/orders" } ] }

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Place order Access root resource Follow orders link $.links[?(@.rel="orders")].href POST /orders

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{ links : [ { rel : "orders", href : "…/orders" } ] }

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{ links : [ { rel : "self", href : "…/orders/4711" }, … { rel : "payment", href : "…/orders/4711/payment" } ], content : { items : [ { drink : "Cappucino", size : "large", milk : "semi" price : 4.2 } ], location : "take-away", price : 4.2 status : "payment expected" } }

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Trigger payment Follow payment link $.links[?(@.rel="payment")].href PUT /orders/4711/payment

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{ links : [ { rel : "self", href : "…/orders/4711" }, … { rel : "payment", href : "…/orders/4711/payment" } ], content : { items : [ { drink : "Cappucino", size : "large", milk : "semi" price : 4.2 } ], location : "take-away", price : 4.2 status : "payment expected" } }

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{ links : [ { rel : "self", href : "…/orders/4711/payment" }, { rel : "order", href : "…/orders/4711" } ], content : { creditCard : [ { number : "1234123412341234", cardHolder : "Oliver Gierke", expiryDate : "2013-11-01" } ], amount : { currency : "EUR", value : 4.2 } } }

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Poll order Follow order link $.links[?(@.rel="order")].href GET /orders/4711 ETag / If-None-Match

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{ links : [ { rel : "self", href : "…/orders/4711/payment" }, { rel : "order", href : "…/orders/4711" } ], content : { creditCard : [ { number : "1234123412341234", cardHolder : "Oliver Gierke", expiryDate : "2013-11-01" } ], amount : { currency : "EUR", value : 4.2 } } }

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{ links : [ { rel : "self", href : "…/orders/4711" } ], content : { items : [ { drink : "Cappucino", size : "large", milk : "semi" price : 4.2 } ], location : "take-away", price : 4.2 status : "preparing" } }

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Poll order Use caching ETag / If-None-Match until…

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{ links : [ { rel : "self", href : "…/orders/4711" }, { rel : "receipt", href : "…/orders/4711/receipt" } ], content : { items : [ { drink : "Cappucino", size : "large", milk : "semi" price : 4.2 } ], location : "take-away", price : 4.2 status : "ready" } }

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Access receipt Follow receipt link $.links[?(@.rel="receipt")].href GET /orders/4711/receipt

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{ links : [ { rel : "self", href : "…/orders/4711" }, { rel : "receipt", href : "…/orders/4711/receipt" } ], content : { items : [ { drink : "Cappucino", size : "large", milk : "semi" price : 4.2 } ], location : "take-away", price : 4.2 status : "ready" } }

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Conclude order Follow receipt link $.links[?(@.rel="receipt")].href DELETE /orders/4711/receipt

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Hypermedia VS. Java Frameworks

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HTTP Methods URI Mapping Content negotiation Hypermedia Spring MVC JAX-RS ✓ ✓ ✓ ✓ ✓ ✓ ? ?

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Spring RESTBucks

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Spring RESTBucks Sample implementation Using Spring technologies http://bit.ly/spring-restbucks

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Web Service Repository - Orders Spring Data Spring Data REST Payment Spring Data Manual implementation Manual implementation

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DEMO

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payment expected preparing cancelled ready completed 1 2 3 4 5 6

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Spring HATEOAS

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Spring HATEOAS Representation models LinkBuilder API Representation enrichment http://bit.ly/spring-hateoas

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Spring Data REST

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Spring Data REST Exports JPA repositories as resources Hypermedia driven representations Extension points http://bit.ly/sd-rest

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REST Shell

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REST Shell Explore REST webservices Hypermedia driven Spring HATEOAS link format brew install rest-shell

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Thank you!

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Resources

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Code Spring RESTBucks Spring Data REST Spring HATEOAS REST Shell

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Books REST in Practice REST und HTTP RESTful WebServices Cookbook Spring Data

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Videos Hypermedia APIs - Jon Moore Hypermedia APIs with Spring