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88 lines
3.4 KiB
Markdown
88 lines
3.4 KiB
Markdown
# Default Middleware
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Any Ring middleware can be used with `reitit-ring`, but using data-driven middleware is preferred as they are easier to manage and in many cases, yield better performance.
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To make web development easier, `reitit-middleware` contains a set of common ring middleware, lifted into data-driven middleware.
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```clj
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[metosin/reitit-middleware "0.2.0-SNAPSHOT"]
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```
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## Exception handling
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A polished version of [compojure-api](https://github.com/metosin/compojure-api) exception handling. Catches all exceptions and invokes configured exception handler.
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```clj
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(require '[reitit.ring.middleware.exception :as exception])
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```
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### `exception/exception-middleware`
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A preconfigured Middleware using `exception/default-handlers`. Catches:
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* request & response [Coercion](coercion.md) exceptions
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* [Muuntaja](https://github.com/metosin/muuntaja) decode exceptions
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* Exceptions with `:type` of `:reitit.ring/response`, returning `:response` key from `ex-data`.
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* safely all other exceptions
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### `exception/create-exception-middleware`
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Creates a reitit middleware that catches all exceptions. Takes a map of `identifier => exception request => response` that is used to select the exception handler for the thown/raised exception identifier. Exception idenfier is either a `Keyword` or a Exception Class.
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The following handlers special handlers are available:
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| key | description
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|--------------|-------------
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| `::default` | a default exception handler if nothing else mathced (default `exception/default-handler`).
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| `::wrap` | a 3-arity handler to wrap the actual handler `handler exception request => response` (no default).
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The handler is selected from the options map by exception idenfitifier in the following lookup order:
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1) `:type` of exception ex-data
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2) Class of exception
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3) `:type` ancestors of exception ex-data
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4) Super Classes of exception
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5) The ::default handler
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```clj
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(require '[reitit.ring.middleware.exception :as exception])
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;; type hierarchy
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(derive ::error ::exception)
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(derive ::failure ::exception)
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(derive ::horror ::exception)
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(defn handler [message exception request]
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{:status 500
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:body {:message message
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:exception (str exception)
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:uri (:uri request)}})
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(exception/create-exception-middleware
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(merge
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exception/default-handlers
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{;; ex-data with :type ::error
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::error (partial handler "error")
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;; ex-data with ::exception or ::failure
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::exception (partial handler "exception")
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;; SQLException and all it's child classes
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java.sql.SQLException (partial handler "sql-exception")
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;; override the default handler
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::exception/default (partial handler "default")
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;; print stack-traces for all exceptions
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::exception/wrap (fn [handler e request]
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(.printStackTrace e)
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(handler e request))}))
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```
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## Content Negotiation
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Wrapper for [Muuntaja](https://github.com/metosin/muuntaja) middleware for content-negotiation, request decoding and response encoding. Reads configuration from route data and emit's [swagger](swagger.md) `:produces` and `:consumes` definitions automatically.
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## Multipart request handling
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Wrapper for [Ring Multipart Middleware](https://github.com/ring-clojure/ring/blob/master/ring-core/src/ring/middleware/multipart_params.clj). Conditionally mounts to an endpoint only if it has `:multipart` params defined. Emits swagger `:consumes` definitions automatically.
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