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BodyCache.scala
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BodyCache.scala
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/*
* Copyright 2014 http4s.org
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.http4s.server.middleware
import cats.arrow.FunctionK
import cats.data.Kleisli
import cats.data.OptionT
import cats.effect.Concurrent
import cats.implicits._
import cats.~>
import org.http4s._
/** Middleware for caching the request body for multiple compilations
*
* As the body of the request is the [[fs2.Stream]] of bytes,
* compiling it several times (e.g. with middlewares) is unsafe.
* This middleware forbids such behaviour, compiling the body only once.
* It does so only for the "inner" middlewares:
*
* {{{
* val route = AMiddleware(BodyCache(SomeOtherMiddleware(myRoute)))
* }}}
*
* In this example only `myRoute` & `SomeOtherMiddleware` will receive cached request body,
* while the `AMiddleware` will get the raw one.
*
* As the entire request body will be allocated in memory,
* there is a possibility of OOM error with a large body.
* Because of that, using the `EntityLimiter` middleware is strongly advised.
*
* @note This middleware has nothing to do with the HTTP caching mechanism
* and it does not cache bodies between multiple requests.
*/
object BodyCache {
def apply[G[_]: Concurrent, F[_]: Concurrent, R](
old: Kleisli[G, R, Response[F]]
)(reqGet: R => Request[F], reqSet: R => Request[F] => R)(
lift: F ~> G
): Kleisli[G, R, Response[F]] = Kleisli {
case req if hasNoBody(reqGet(req)) => old(req)
case req => lift(compileBody(reqGet(req))).flatMap(reqSet(req).andThen(old.run))
}
def httpRoutes[F[_]: Concurrent](routes: HttpRoutes[F]): HttpRoutes[F] =
apply(routes)(identity, _ => identity)(OptionT.liftK)
def contextRoutes[T, F[_]: Concurrent](routes: ContextRoutes[T, F]): ContextRoutes[T, F] =
apply(routes)(_.req, in => cached => in.copy(req = cached))(OptionT.liftK)
def httpApp[F[_]: Concurrent](app: HttpApp[F]): HttpApp[F] =
apply(app)(identity, _ => identity)(FunctionK.id)
private def compileBody[F[_]: Concurrent](req: Request[F]): F[Request[F]] =
req.toStrict(None)
def hasNoBody[F[_]](req: Request[F]): Boolean =
req.contentLength.contains(0L)
}