" What needs to be done to make the REST architectural style - - PowerPoint PPT Presentation

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" What needs to be done to make the REST architectural style - - PowerPoint PPT Presentation

Sep 26, 2022 296 likes •864 views

" What needs to be done to make the REST architectural style clear on the notion that hypertext is a constraint? In other words, if the engine of application state (and hence the API) is not being driven by hypertext, then it cannot

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"

What needs to be done to make the REST architectural style clear on the notion that hypertext is a constraint? In

  • ther words, if the engine of application state (and hence

the API) is not being driven by hypertext, then it cannot be RESTful and cannot be a REST API. Period. Is there some broken manual somewhere that needs to be fixed?
 


– Roy T. Fielding

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REST Assured

Hypermedia APIs with Spring

  • Oliver Gierke
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Oliver Gierke

Engineer @ Pivotal Spring Data project lead

  • gierke@gopivotal.com

www.olivergierke.de

  • livergierke
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Background

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REST

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REST

Resources URIs Uniform Interface Representations

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Hypermedia

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"

HATEOAS - the word, there's no pronunciation for.

  • – Ben Hale (SpringOne2GX 2012)
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Hypermedia

Links in representations State navigations discoverable

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{ _links : { self : { href : … }, cancel : { href : … }, update : { href : … }, payment : { href : "…/orders/4711/payment" } },

  • items : [ {

… } ],

  • location : "take-away",

price : 4.2, status : "payment expected" }

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MediaType

text/html application/hal+(json|xml) application/collection+json

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Implementation aspects

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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 HATEOAS

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Spring HATEOAS

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

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DEMO

https:/ /github.com/olivergierke/spring- hateoas-sample

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Spring Data REST

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Spring Data REST

Export Spring Data repositories in a hypermedia-driven way Do „the right thing™“ by default

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DEMO

https:/ /github.com/olivergierke/rest- microservices

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REST in practice

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RESTBucks

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RESTBucks

Starbucks (like) coffee ordering Order / Payment

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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

(only if "payment expected")

4 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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  • rders

Returns all orders available in the system

  • rder

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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  • rders

Returns all orders available in the system

  • rder

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

(only if "payment expected")

4 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

  • rders

Create new order 1 POST/PATCH update Update the order

(only if "payment expected")

2 DELETE cancel Cancel order

(only if "payment expected")

3 PUT payment Pay order

(only if "payment expected")

4 Barista preparing the order GET

  • rder

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“?

  • Clients react on the presence of links
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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

https:/ /github.com/olivergierke/spring- restbucks

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API docs?

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"

How does the client make sense of all this?

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Profiles

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Profiles

RFC 6906 Points to resources describing additional semantics within a media type

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Curies

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(HAL) Curies

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{ "_links" : { "self" : { "href" : … }, "restbucks:cancel" : { "href" : … }, "restbucks:update" : { "href" : … },

  • "curies" : {

"name" : "restbucks", "href" : "…/rels/{rel}" "templated" : true } }, … }

Docs for update are at: …/rels/update

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alps.io

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alps.io

Application Level Profile Semantics Describe state transitions and payloads Media type agnostic Repository with pre-defined docs application/alps+(json|xml)

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DEMO

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Miscellaneous

Spring MVC integration testing REST Shell

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Thank you!

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Resources

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Code

Spring HATEOAS Sample REST micro-services Spring RESTBucks

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Books

RESTful Web APIs REST in Practice REST und HTTP

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Videos

Hypermedia APIs - Jon Moore Hypermedia APIs with Spring