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< h1 id = "parameter-coercion" > Parameter coercion< / h1 >
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< p > Reitit provides pluggable parameter coercion via < code > reitit.ring.coercion.protocol/Coercion< / code > protocol, originally introduced in < a href = "https://clojars.org/metosin/compojure-api" target = "_blank" > compojure-api< / a > . Reitit ships with < code > reitit.ring.coercion.spec/SpecCoercion< / code > providing implemenation for < a href = "https://clojure.org/about/spec" target = "_blank" > clojure.spec< / a > and < a href = "https://github.com/metosin/spec-tools#data-specs" target = "_blank" > data-specs< / a > .< / p >
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< p > < strong > NOTE< / strong > : Before Clojure 1.9.0 is shipped, to use the spec-coercion, one needs to add the following dependencies manually to the project:< / p >
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< pre > < code class = "lang-clj" > [org.clojure/clojure < span class = "hljs-string" > " 1.9.0-beta2" < / span > ]
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[org.clojure/spec.alpha < span class = "hljs-string" > " 0.1.123" < / span > ]
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[metosin/spec-tools < span class = "hljs-string" > " 0.4.0" < / span > ]
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< / code > < / pre >
< h3 id = "ring-request-and-response-coercion" > Ring request and response coercion< / h3 >
< p > To use < code > Coercion< / code > with Ring, one needs to do the following:< / p >
< ol >
< li > Define parameters and responses as data into route meta-data, in format adopted from < a href = "https://github.com/metosin/ring-swagger#more-complete-example" target = "_blank" > ring-swagger< / a > :< ul >
< li > < code > :parameters< / code > map, with submaps for different parameters: < code > :query< / code > , < code > :body< / code > , < code > :form< / code > , < code > :header< / code > and < code > :path< / code > . Parameters are defined in the format understood by the < code > Coercion< / code > .< / li >
< li > < code > :responses< / code > map, with response status codes as keys (or < code > :default< / code > for " everything else" ) with maps with < code > :schema< / code > and optionally < code > :description< / code > as values.< / li >
< / ul >
< / li >
< li > Define a < code > Coercion< / code > to route meta-data under < code > :coercion< / code > < / li >
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< li > Mount request & response coercion middleware to the routes (recommended to mount to all routes under router as they mounted only to routes which have the parameters / responses defined):< ul >
< li > < code > reitit.ring.coercion/gen-wrap-coerce-parameters< / code > < / li >
< li > < code > gen-wrap-coerce-parameters/gen-wrap-coerce-responses< / code > < / li >
< / ul >
< / li >
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< / ol >
< p > If the request coercion succeeds, the coerced parameters are injected into request under < code > :parameters< / code > .< / p >
< p > If either request or response coercion fails, an descriptive error is thrown.< / p >
< h4 id = "example-with-data-specs" > Example with data-specs< / h4 >
< pre > < code class = "lang-clj" > (< span class = "hljs-name" > require< / span > ' [reitit.ring < span class = "hljs-symbol" > :as< / span > ring])
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(< span class = "hljs-name" > require< / span > ' [reitit.ring.coercion < span class = "hljs-symbol" > :as< / span > coercion])
(< span class = "hljs-name" > require< / span > ' [reitit.ring.coercion.spec < span class = "hljs-symbol" > :as< / span > spec])
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(< span class = "hljs-name" > < span class = "hljs-builtin-name" > def< / span > < / span > app
(< span class = "hljs-name" > ring/ring-handler< / span >
(< span class = "hljs-name" > ring/router< / span >
[< span class = "hljs-string" > " /api" < / span >
[< span class = "hljs-string" > " /ping" < / span > {< span class = "hljs-symbol" > :parameters< / span > {< span class = "hljs-symbol" > :body< / span > {< span class = "hljs-symbol" > :x< / span > int?, < span class = "hljs-symbol" > :y< / span > int?}}
< span class = "hljs-symbol" > :responses< / span > {< span class = "hljs-number" > 200< / span > {< span class = "hljs-symbol" > :schema< / span > {< span class = "hljs-symbol" > :total< / span > pos-int?}}}
< span class = "hljs-symbol" > :get< / span > {< span class = "hljs-symbol" > :handler< / span > (< span class = "hljs-name" > < span class = "hljs-builtin-name" > fn< / span > < / span > [{{{< span class = "hljs-symbol" > :keys< / span > [x y]} < span class = "hljs-symbol" > :body< / span > } < span class = "hljs-symbol" > :parameters< / span > }]
{< span class = "hljs-symbol" > :status< / span > < span class = "hljs-number" > 200< / span >
< span class = "hljs-symbol" > :body< / span > {< span class = "hljs-symbol" > :total< / span > (< span class = "hljs-name" > < span class = "hljs-builtin-name" > +< / span > < / span > x y)}})}}]]
{< span class = "hljs-symbol" > :meta< / span > {< span class = "hljs-symbol" > :middleware< / span > [coercion/gen-wrap-coerce-parameters
coercion/gen-wrap-coerce-response]
< span class = "hljs-symbol" > :coercion< / span > spec/coercion}})))
< / code > < / pre >
< pre > < code class = "lang-clj" > (< span class = "hljs-name" > app< / span >
{< span class = "hljs-symbol" > :request-method< / span > < span class = "hljs-symbol" > :get< / span >
< span class = "hljs-symbol" > :uri< / span > < span class = "hljs-string" > " /api/ping" < / span >
< span class = "hljs-symbol" > :body-params< / span > {< span class = "hljs-symbol" > :x< / span > < span class = "hljs-number" > 1< / span > , < span class = "hljs-symbol" > :y< / span > < span class = "hljs-number" > 2< / span > }})
< span class = "hljs-comment" > ; {:status 200, :body {:total 3}}< / span >
< / code > < / pre >
< h4 id = "example-with-specs" > Example with specs< / h4 >
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< p > Currently, < code > clojure.spec< / code > < a href = "https://dev.clojure.org/jira/browse/CLJ-2116" target = "_blank" > doesn' t support runtime transformations via conforming< / a > , so one needs to wrap all specs with < code > spec-tools.core/spec< / code > .< / p >
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< pre > < code class = "lang-clj" > (< span class = "hljs-name" > require< / span > ' [reitit.ring < span class = "hljs-symbol" > :as< / span > ring])
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(< span class = "hljs-name" > require< / span > ' [reitit.ring.coercion < span class = "hljs-symbol" > :as< / span > coercion])
(< span class = "hljs-name" > require< / span > ' [reitit.ring.coercion.spec < span class = "hljs-symbol" > :as< / span > spec])
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(< span class = "hljs-name" > require< / span > ' [clojure.spec.alpha < span class = "hljs-symbol" > :as< / span > s])
(< span class = "hljs-name" > require< / span > ' [spec-tools.core < span class = "hljs-symbol" > :as< / span > st])
(< span class = "hljs-name" > s/def< / span > < span class = "hljs-symbol" > ::x< / span > (< span class = "hljs-name" > st/spec< / span > int?))
(< span class = "hljs-name" > s/def< / span > < span class = "hljs-symbol" > ::y< / span > (< span class = "hljs-name" > st/spec< / span > int?))
(< span class = "hljs-name" > s/def< / span > < span class = "hljs-symbol" > ::total< / span > int?)
(< span class = "hljs-name" > s/def< / span > < span class = "hljs-symbol" > ::request< / span > (< span class = "hljs-name" > s/keys< / span > < span class = "hljs-symbol" > :req-un< / span > [< span class = "hljs-symbol" > ::x< / span > < span class = "hljs-symbol" > ::y< / span > ]))
(< span class = "hljs-name" > s/def< / span > < span class = "hljs-symbol" > ::response< / span > (< span class = "hljs-name" > s/keys< / span > < span class = "hljs-symbol" > :req-un< / span > [< span class = "hljs-symbol" > ::total< / span > ]))
(< span class = "hljs-name" > < span class = "hljs-builtin-name" > def< / span > < / span > app
(< span class = "hljs-name" > ring/ring-handler< / span >
(< span class = "hljs-name" > ring/router< / span >
[< span class = "hljs-string" > " /api" < / span >
[< span class = "hljs-string" > " /ping" < / span > {< span class = "hljs-symbol" > :parameters< / span > {< span class = "hljs-symbol" > :body< / span > < span class = "hljs-symbol" > ::request< / span > }
< span class = "hljs-symbol" > :responses< / span > {< span class = "hljs-number" > 200< / span > {< span class = "hljs-symbol" > :schema< / span > < span class = "hljs-symbol" > ::response< / span > }}
< span class = "hljs-symbol" > :get< / span > {< span class = "hljs-symbol" > :handler< / span > (< span class = "hljs-name" > < span class = "hljs-builtin-name" > fn< / span > < / span > [{{{< span class = "hljs-symbol" > :keys< / span > [x y]} < span class = "hljs-symbol" > :body< / span > } < span class = "hljs-symbol" > :parameters< / span > }]
{< span class = "hljs-symbol" > :status< / span > < span class = "hljs-number" > 200< / span >
< span class = "hljs-symbol" > :body< / span > {< span class = "hljs-symbol" > :total< / span > (< span class = "hljs-name" > < span class = "hljs-builtin-name" > +< / span > < / span > x y)}})}}]]
{< span class = "hljs-symbol" > :meta< / span > {< span class = "hljs-symbol" > :middleware< / span > [coercion/gen-wrap-coerce-parameters
coercion/gen-wrap-coerce-response]
< span class = "hljs-symbol" > :coercion< / span > spec/coercion}})))
< / code > < / pre >
< pre > < code class = "lang-clj" > (< span class = "hljs-name" > app< / span >
{< span class = "hljs-symbol" > :request-method< / span > < span class = "hljs-symbol" > :get< / span >
< span class = "hljs-symbol" > :uri< / span > < span class = "hljs-string" > " /api/ping" < / span >
< span class = "hljs-symbol" > :body-params< / span > {< span class = "hljs-symbol" > :x< / span > < span class = "hljs-number" > 1< / span > , < span class = "hljs-symbol" > :y< / span > < span class = "hljs-number" > 2< / span > }})
< span class = "hljs-comment" > ; {:status 200, :body {:total 3}}< / span >
< / code > < / pre >
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