HTTP Model
Apache Pekko HTTP model contains a deeply structured, fully immutable, case-class based model of all the major HTTP data structures, like HTTP requests, responses and common headers. It lives in the pekko-http-core module and forms the basis for most of Apache Pekko HTTP’s APIs.
Overview¶
Since pekko-http-core provides the central HTTP data structures you will find the following import in quite a few places around the code base (and probably your own code as well):
sourceimport org.apache.pekko.http.scaladsl.model._
sourceimport org.apache.pekko.http.javadsl.model.*;
import org.apache.pekko.http.javadsl.model.headers.*;
import java.util.Optional;
This brings all of the most relevant types in scope, mainly:
HttpRequest
andHttpResponse
, the central message modelheaders
, the package containing all the predefined HTTP header models and supporting types- Supporting types like
Uri
,HttpMethods
,MediaTypes
,StatusCodes
, etc.
A common pattern is that the model of a certain entity is represented by an immutable type (class or trait), while the actual instances of the entity defined by the HTTP spec live in an accompanying object carrying the name of the type plus a trailing plural ‘s’.
For example:
- Defined
HttpMethod
instances live in theHttpMethods
object . - Defined
HttpCharset
instances live in theHttpCharsets
object . - Defined
HttpEncoding
instances live in theHttpEncodings
object . - Defined
HttpProtocol
instances live in theHttpProtocols
object . - Defined
MediaType
instances live in theMediaTypes
object . - Defined
StatusCode
instances live in theStatusCodes
object .
HttpRequest¶
HttpRequest
and HttpResponse
are the basic case classes representing HTTP messages.
An HttpRequest
consists of
- a method (GET, POST, etc.)
- a URI (see URI model for more information)
- a seq of headers
- an entity (body data)
- a protocol
Here are some examples how to construct an HttpRequest
:
sourceimport org.apache.pekko.http.scaladsl.model._
import HttpMethods._
// construct a simple GET request to `homeUri`
val homeUri = Uri("/abc")
HttpRequest(GET, uri = homeUri)
// construct simple GET request to "/index" (implicit string to Uri conversion)
HttpRequest(GET, uri = "/index")
// construct simple POST request containing entity
val data = ByteString("abc")
HttpRequest(POST, uri = "/receive", entity = data)
// customize every detail of HTTP request
import HttpProtocols._
import MediaTypes._
import HttpCharsets._
val userData = ByteString("abc")
val authorization = headers.Authorization(BasicHttpCredentials("user", "pass"))
HttpRequest(
PUT,
uri = "/user",
entity = HttpEntity(`text/plain`.withCharset(`UTF-8`), userData),
headers = List(authorization),
protocol = `HTTP/1.0`)
sourceimport org.apache.pekko.http.javadsl.model.*;
import org.apache.pekko.http.javadsl.model.headers.*;
import java.util.Optional;
// construct a simple GET request to `homeUri`
Uri homeUri = Uri.create("/home");
HttpRequest request1 = HttpRequest.create().withUri(homeUri);
// construct simple GET request to "/index" using helper methods
HttpRequest request2 = HttpRequest.GET("/index");
// construct simple POST request containing entity
ByteString data = ByteString.fromString("abc");
HttpRequest postRequest1 = HttpRequest.POST("/receive").withEntity(data);
// customize every detail of HTTP request
// import HttpProtocols.*
// import MediaTypes.*
Authorization authorization = Authorization.basic("user", "pass");
HttpRequest complexRequest =
HttpRequest.PUT("/user")
.withEntity(HttpEntities.create(ContentTypes.TEXT_PLAIN_UTF8, "abc"))
.addHeader(authorization)
.withProtocol(HttpProtocols.HTTP_1_0);
All parameters of HttpRequest.apply
have default values set, so headers
for example don’t need to be specified if there are none. Many of the parameters types (like HttpEntity
and Uri
) define implicit conversions for common use cases to simplify the creation of request and response instances.
There are certain environments where it is easy to inadvertently print, write or log entries built out of string representations of HttpRequest
instances. On the other hand, it is not uncommon for HTTP headers and entities to contain Personal Identifying Information (PII) or Sensitive Personal Information (SPI) .
To avoid accidentally leaking such information, these fields are omitted from HttpRequest
toString
output.
If needed, it is possible to define a custom string representation including all fields as shown in the following example:
source/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* license agreements; and to You under the Apache License, version 2.0:
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* This file is part of the Apache Pekko project, which was derived from Akka.
*/
/*
* Copyright (C) 2009-2022 Lightbend Inc. <https://www.lightbend.com>
*/
package docs.http.scaladsl
import org.apache.pekko
import pekko.http.scaladsl.model.{ HttpEntity, HttpRequest }
import pekko.http.scaladsl.model.headers.{ Authorization, BasicHttpCredentials }
import pekko.testkit.PekkoSpec
import scala.collection.immutable
class HttpRequestDetailedStringExampleSpec extends PekkoSpec {
// Custom string representation which includes headers
def toDetailedString(request: HttpRequest): String = {
import request._
s"""HttpRequest(${_1},${_2},${_3},${_4},${_5})"""
}
"Include headers in custom string representation" in {
// An HTTP header containing Personal Identifying Information
val piiHeader = Authorization(BasicHttpCredentials("user", "password"))
// An HTTP entity containing Personal Identifying Information
val piiBody: HttpEntity.Strict =
"This body contains information about [user]"
val httpRequestWithHeadersAndBody =
HttpRequest(entity = piiBody, headers = immutable.Seq(piiHeader))
// Our custom string representation includes body and headers string representations...
assert(
toDetailedString(httpRequestWithHeadersAndBody)
.contains(piiHeader.toString))
assert(
toDetailedString(httpRequestWithHeadersAndBody).contains(piiBody.toString))
// ... while default `toString` doesn't.
assert(!s"$httpRequestWithHeadersAndBody".contains(piiHeader.unsafeToString))
assert(!s"$httpRequestWithHeadersAndBody".contains(piiBody.data.utf8String))
}
}
source/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* license agreements; and to You under the Apache License, version 2.0:
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* This file is part of the Apache Pekko project, which was derived from Akka.
*/
/*
* Copyright (C) 2009-2022 Lightbend Inc. <https://www.lightbend.com>
*/
package docs.http.javadsl;
import org.apache.pekko.http.javadsl.model.*;
import org.apache.pekko.http.javadsl.model.headers.Authorization;
import org.junit.Test;
import static org.junit.Assert.*;
import java.util.Arrays;
public class HttpRequestDetailedStringExampleTest {
// Custom string representation which includes headers
public String toDetailedString(HttpRequest request) {
HttpMethod method = request.method();
Uri uri = request.getUri();
Iterable<HttpHeader> headers = request.getHeaders();
RequestEntity entity = request.entity();
HttpProtocol protocol = request.protocol();
return String.format("HttpRequest(%s, %s, %s, %s, %s)", method, uri, headers, entity, protocol);
}
@Test
public void headersInCustomStringRepresentation() {
// An HTTP header containing Personal Identifying Information
Authorization piiHeader = Authorization.basic("user", "password");
// An HTTP entity containing Personal Identifying Information
HttpEntity.Strict piiBody = HttpEntities.create("This body contains information about [user]");
HttpRequest httpRequestWithHeadersAndBody =
HttpRequest.create().withEntity(piiBody).withHeaders(Arrays.asList(piiHeader));
// Our custom string representation includes body and headers string representations...
assertTrue(toDetailedString(httpRequestWithHeadersAndBody).contains(piiHeader.toString()));
assertTrue(toDetailedString(httpRequestWithHeadersAndBody).contains(piiBody.toString()));
// ... while default `toString` doesn't.
assertFalse(httpRequestWithHeadersAndBody.toString().contains(piiHeader.unsafeToString()));
assertFalse(httpRequestWithHeadersAndBody.toString().contains(piiBody.getData().utf8String()));
}
}
Synthetic Headers¶
In some cases it may be necessary to deviate from fully RFC-Compliant behavior. For instance, Amazon S3 treats the +
character in the path part of the URL as a space, even though the RFC specifies that this behavior should be limited exclusively to the query portion of the URI.
In order to work around these types of edge cases, Apache Pekko HTTP provides for the ability to provide extra, non-standard information to the request via synthetic headers. These headers are not passed to the client but are instead consumed by the request engine and used to override default behavior.
For instance, in order to provide a raw request URI, bypassing the default URL normalization, you could do the following:
sourceimport org.apache.pekko.http.scaladsl.model.headers.`Raw-Request-URI`
val req = HttpRequest(uri = "/ignored", headers = List(`Raw-Request-URI`("/a/b%2Bc")))
source// imports org.apache.pekko.http.javadsl.model.headers.RawRequestURI
HttpRequest.create("/ignored").addHeader(RawRequestURI.create("/a/b%2Bc"));
HttpResponse¶
An HttpResponse
consists of
- a status code
- a
Seq
of headers - an entity (body data)
- a protocol
Here are some examples how to construct an HttpResponse
:
sourceimport StatusCodes._
// simple OK response without data created using the integer status code
HttpResponse(200)
// 404 response created using the named StatusCode constant
HttpResponse(NotFound)
// 404 response with a body explaining the error
HttpResponse(404, entity = "Unfortunately, the resource couldn't be found.")
// A redirecting response containing an extra header
val locationHeader = headers.Location("http://example.com/other")
HttpResponse(Found, headers = List(locationHeader))
source// simple OK response without data created using the integer status code
HttpResponse ok = HttpResponse.create().withStatus(200);
// 404 response created using the named StatusCode constant
HttpResponse notFound = HttpResponse.create().withStatus(StatusCodes.NOT_FOUND);
// 404 response with a body explaining the error
HttpResponse notFoundCustom =
HttpResponse.create()
.withStatus(404)
.withEntity("Unfortunately, the resource couldn't be found.");
// A redirecting response containing an extra header
Location locationHeader = Location.create("http://example.com/other");
HttpResponse redirectResponse =
HttpResponse.create().withStatus(StatusCodes.FOUND).addHeader(locationHeader);
In addition to the simple HttpEntity
constructors which create an entity from a fixed String
or ByteString
as shown here the Apache Pekko HTTP model defines a number of subclasses of HttpEntity
which allow body data to be specified as a stream of bytes.
There are certain environments where it is easy to inadvertently print, write or log entries built out of string representations of HttpResponse
instances. On the other hand, it is not uncommon for HTTP headers and entities to contain Personal Identifying Information (PII) or Sensitive Personal Information (SPI) .
To avoid accidentally leaking such information, these fields are omitted from HttpResponse
toString
output.
If needed, it is possible to define a custom string representation including all fields as shown in the following example:
source/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* license agreements; and to You under the Apache License, version 2.0:
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* This file is part of the Apache Pekko project, which was derived from Akka.
*/
/*
* Copyright (C) 2009-2022 Lightbend Inc. <https://www.lightbend.com>
*/
package docs.http.scaladsl
import org.apache.pekko
import pekko.http.scaladsl.model.{ HttpEntity, HttpResponse }
import pekko.http.scaladsl.model.headers.{ Authorization, BasicHttpCredentials }
import pekko.testkit.PekkoSpec
import scala.collection.immutable
class HttpResponseDetailedStringExampleSpec extends PekkoSpec {
// Custom string representation which includes headers
def toDetailedString(response: HttpResponse): String = {
import response._
s"""HttpResponse(${_1},${_2},${_3},${_4})"""
}
"Include headers in custom string representation" in {
// An HTTP header containing Personal Identifying Information
val piiHeader = Authorization(BasicHttpCredentials("user", "password"))
// An HTTP entity containing Personal Identifying Information
val piiBody: HttpEntity.Strict =
"This body contains information about [user]"
val httpResponseWithHeadersAndBody =
HttpResponse(entity = piiBody, headers = immutable.Seq(piiHeader))
// Our custom string representation includes body and headers string representations...
assert(
toDetailedString(httpResponseWithHeadersAndBody)
.contains(piiHeader.toString))
assert(
toDetailedString(httpResponseWithHeadersAndBody)
.contains(piiBody.toString))
// ... while default `toString` doesn't.
assert(!s"$httpResponseWithHeadersAndBody".contains(piiHeader.unsafeToString))
assert(!s"$httpResponseWithHeadersAndBody".contains(piiBody.data.utf8String))
}
}
source/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* license agreements; and to You under the Apache License, version 2.0:
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* This file is part of the Apache Pekko project, which was derived from Akka.
*/
/*
* Copyright (C) 2009-2022 Lightbend Inc. <https://www.lightbend.com>
*/
package docs.http.javadsl;
import org.apache.pekko.http.javadsl.model.*;
import org.apache.pekko.http.javadsl.model.headers.Authorization;
import org.junit.Test;
import java.util.Arrays;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;
public class HttpResponseDetailedStringExampleTest {
// Custom string representation which includes headers
public String toDetailedString(HttpResponse response) {
StatusCode status = response.status();
Iterable<HttpHeader> headers = response.getHeaders();
HttpEntity entity = response.entity();
HttpProtocol protocol = response.protocol();
return String.format("HttpResponse(%s, %s, %s, %s)", status, headers, entity, protocol);
}
@Test
public void headersInCustomStringRepresentation() {
// An HTTP header containing Personal Identifying Information
Authorization piiHeader = Authorization.basic("user", "password");
// An HTTP entity containing Personal Identifying Information
HttpEntity.Strict piiBody = HttpEntities.create("This body contains information about [user]");
HttpResponse httpResponseWithHeadersAndBody =
HttpResponse.create().withEntity(piiBody).withHeaders(Arrays.asList(piiHeader));
// Our custom string representation includes body and headers string representations...
assertTrue(toDetailedString(httpResponseWithHeadersAndBody).contains(piiHeader.toString()));
assertTrue(toDetailedString(httpResponseWithHeadersAndBody).contains(piiBody.toString()));
// ... while default `toString` doesn't.
assertFalse(httpResponseWithHeadersAndBody.toString().contains(piiHeader.unsafeToString()));
assertFalse(httpResponseWithHeadersAndBody.toString().contains(piiBody.getData().utf8String()));
}
}
HttpEntity¶
An HttpEntity
carries the data bytes of a message together with its Content-Type and, if known, its Content-Length. In Apache Pekko HTTP, there are five different kinds of entities which model the various ways that message content can be received or sent:
- HttpEntity.Strict
- The simplest entity, which is used when all the entity are already available in memory. It wraps a plain
ByteString
and represents a standard, unchunked entity with a knownContent-Length
. - HttpEntity.Default
- The general, unchunked HTTP/1.1 message entity. It has a known length and presents its data as a
Source[ByteString, _]
which can be only materialized once. It is an error if the provided source doesn’t produce exactly as many bytes as specified. The distinction ofStrict
andDefault
is an API-only one. On the wire, both kinds of entities look the same. - HttpEntity.Chunked
- The model for HTTP/1.1 chunked content (i.e. sent with
Transfer-Encoding: chunked
). The content length is unknown and the individual chunks are presented as aSource[HttpEntity.ChunkStreamPart]
. AChunkStreamPart
is either a non-emptyChunk
or aLastChunk
containing optional trailer headers. The stream consists of zero or moreChunked
parts and can be terminated by an optionalLastChunk
part . - HttpEntity.CloseDelimited
- An unchunked entity of unknown length that is implicitly delimited by closing the connection (
Connection: close
). The content data are presented as aSource[ByteString, _]
. Since the connection must be closed after sending an entity of this type it can only be used on the server-side for sending a response. Also, the main purpose ofCloseDelimited
entities is compatibility with HTTP/1.0 peers, which do not support chunked transfer encoding. If you are building a new application and are not constrained by legacy requirements you shouldn’t rely onCloseDelimited
entities, since implicit terminate-by-connection-close is not a robust way of signaling response end, especially in the presence of proxies. Additionally this type of entity prevents connection reuse which can seriously degrade performance. UseHttpEntity.Chunked
instead! - HttpEntity.IndefiniteLength
- A streaming entity of unspecified length for use in a
Multipart.BodyPart
.
Entity types Strict
, Default
, and Chunked
are a subtype of HttpEntity.Regular
which allows to use them for requests and responses. In contrast, HttpEntity.CloseDelimited
can only be used for responses.
Streaming entity types (i.e. all but Strict
) cannot be shared or serialized. To create a strict, shareable copy of an entity or message use HttpEntity.toStrict
or HttpMessage.toStrict
which returns a Future
of the object with the body data collected into a ByteString
.
The HttpEntity
companion object contains several helper constructors to create entities from common types easily.
You can pattern match over the subtypes of HttpEntity
if you want to provide special handling for each of the subtypes. However, in many cases a recipient of an HttpEntity
doesn’t care about of which subtype an entity is (and how data is transported exactly on the HTTP layer). Therefore, the general method HttpEntity.dataBytes
is provided which returns a Source[ByteString, _]
that allows access to the data of an entity regardless of its concrete subtype.
- Use
Strict
if the amount of data is “small” and already available in memory (e.g. as aString
orByteString
) - Use
Default
if the data is generated by a streaming data source and the size of the data is known - Use
Chunked
for an entity of unknown length - Use
CloseDelimited
for a response as a legacy alternative toChunked
if the client doesn’t support chunked transfer encoding. Otherwise useChunked
! - In a
Multipart.BodyPart
useIndefiniteLength
for content of unknown length.
When you receive a non-strict message from a connection then additional data are only read from the network when you request them by consuming the entity data stream. This means that, if you don’t consume the entity stream then the connection will effectively be stalled. In particular no subsequent message (request or response) will be read from the connection as the entity of the current message “blocks” the stream. Therefore you must make sure that you always consume the entity data, even in the case that you are not actually interested in it!
Limiting message entity length¶
All message entities that Apache Pekko HTTP reads from the network automatically get a length verification check attached to them. This check makes sure that the total entity size is less than or equal to the configured max-content-length
[1], which is an important defense against certain Denial-of-Service attacks. However, a single global limit for all requests (or responses) is often too inflexible for applications that need to allow large limits for some requests (or responses) but want to clamp down on all messages not belonging into that group.
In order to give you maximum flexibility in defining entity size limits according to your needs the HttpEntity
features a withSizeLimit
method, which lets you adjust the globally configured maximum size for this particular entity, be it to increase or decrease any previously set value. This means that your application will receive all requests (or responses) from the HTTP layer, even the ones whose Content-Length
exceeds the configured limit (because you might want to increase the limit yourself). Only when the actual data stream Source
contained in the entity is materialized will the boundary checks be actually applied. In case the length verification fails the respective stream will be terminated with an EntityStreamSizeException
either directly at materialization time (if the Content-Length
is known) or whenever more data bytes than allowed have been read.
When called on Strict
entities the withSizeLimit
method will return the entity itself if the length is within the bound, otherwise a Default
entity with a single element data stream. This allows for potential refinement of the entity size limit at a later point (before materialization of the data stream).
By default all message entities produced by the HTTP layer automatically carry the limit that is defined in the application’s max-content-length
config setting. If the entity is transformed in a way that changes the content-length and then another limit is applied then this new limit will be evaluated against the new content-length. If the entity is transformed in a way that changes the content-length and no new limit is applied then the previous limit will be applied against the previous content-length. Generally this behavior should be in line with your expectations.
[1] pekko.http.parsing.max-content-length (applying to server- as well as client-side), pekko.http.server.parsing.max-content-length (server-side only), pekko.http.client.parsing.max-content-length (client-side only) or pekko.http.host-connection-pool.client.parsing.max-content-length (only host-connection-pools)
Special processing for HEAD requests¶
RFC 7230 defines very clear rules for the entity length of HTTP messages.
Especially this rule requires special treatment in Apache Pekko HTTP:
Any response to a HEAD request and any response with a 1xx (Informational), 204 (No Content), or 304 (Not Modified) status code is always terminated by the first empty line after the header fields, regardless of the header fields present in the message, and thus cannot contain a message body.
Responses to HEAD requests introduce the complexity that Content-Length or Transfer-Encoding headers can be present but the entity is empty. This is modeled by allowing HttpEntity.Default and HttpEntity.Chunked to be used for HEAD responses with an empty data stream.
Also, when a HEAD response has an HttpEntity.CloseDelimited entity the Apache Pekko HTTP implementation will not close the connection after the response has been sent. This allows the sending of HEAD responses without Content-Length header across persistent HTTP connections.
Header Model¶
Apache Pekko HTTP contains a rich model of the most common HTTP headers. Parsing and rendering is done automatically so that applications don’t need to care for the actual syntax of headers. Headers not modelled explicitly are represented as a RawHeader
, which is essentially a String/String name/value pair.
See these examples of how to deal with headers:
sourceimport org.apache.pekko.http.scaladsl.model.headers._
// create a ``Location`` header
val loc = Location("http://example.com/other")
// create an ``Authorization`` header with HTTP Basic authentication data
val auth = Authorization(BasicHttpCredentials("joe", "josepp"))
// custom type
case class User(name: String, pass: String)
// a method that extracts basic HTTP credentials from a request
def credentialsOfRequest(req: HttpRequest): Option[User] =
for {
case Authorization(BasicHttpCredentials(user, pass)) <- req.header[Authorization]
} yield User(user, pass)
source // create a ``Location`` header
Location locationHeader = Location.create("http://example.com/other");
// create an ``Authorization`` header with HTTP Basic authentication data
Authorization authorization = Authorization.basic("user", "pass");
// a method that extracts basic HTTP credentials from a request
private Optional<BasicHttpCredentials> getCredentialsOfRequest(HttpRequest request) {
Optional<Authorization> auth = request.getHeader(Authorization.class);
if (auth.isPresent() && auth.get().credentials() instanceof BasicHttpCredentials)
return Optional.of((BasicHttpCredentials) auth.get().credentials());
else return Optional.empty();
}
HTTP Headers¶
When the Apache Pekko HTTP server receives an HTTP request it tries to parse all its headers into their respective model classes. Independently of whether this succeeds or not, the HTTP layer will always pass on all received headers to the application. Unknown headers as well as ones with invalid syntax (according to the header parser) will be made available as RawHeader
instances. For the ones exhibiting parsing errors a warning message is logged depending on the value of the illegal-header-warnings
config setting.
Some headers have special status in HTTP and are therefore treated differently from “regular” headers:
- Content-Type
- The Content-Type of an HTTP message is modeled as the
contentType
field of theHttpEntity
. TheContent-Type
header therefore doesn’t appear in theheaders
sequence of a message. Also, aContent-Type
header instance that is explicitly added to theheaders
of a request or response will not be rendered onto the wire and trigger a warning being logged instead! - Transfer-Encoding
- Messages with
Transfer-Encoding: chunked
are represented via theHttpEntity.Chunked
entity. As such chunked messages that do not have another deeper nested transfer encoding will not have aTransfer-Encoding
header in theirheaders
sequence . Similarly, aTransfer-Encoding
header instance that is explicitly added to theheaders
of a request or response will not be rendered onto the wire and trigger a warning being logged instead! - Content-Length
- The content length of a message is modelled via its HttpEntity. As such no
Content-Length
header will ever be part of a message’sheader
sequence. Similarly, aContent-Length
header instance that is explicitly added to theheaders
of a request or response will not be rendered onto the wire and trigger a warning being logged instead! - Server
- A
Server
header is usually added automatically to any response and its value can be configured via thepekko.http.server.server-header
setting. Additionally an application can override the configured header with a custom one by adding it to the response’sheader
sequence. - User-Agent
- A
User-Agent
header is usually added automatically to any request and its value can be configured via thepekko.http.client.user-agent-header
setting. Additionally an application can override the configured header with a custom one by adding it to the request’sheader
sequence. - Date
- The
Date
response header is added automatically but can be overridden by supplying it manually. - Connection
- On the server-side Apache Pekko HTTP watches for explicitly added
Connection: close
response headers and as such honors the potential wish of the application to close the connection after the respective response has been sent out. The actual logic for determining whether to close the connection is quite involved. It takes into account the request’s method, protocol and potentialConnection
header as well as the response’s protocol, entity and potentialConnection
header. See this test for a full table of what happens when. - Strict-Transport-Security
- HTTP Strict Transport Security (HSTS) is a web security policy mechanism which is communicated by the
Strict-Transport-Security
header. The most important security vulnerability that HSTS can fix is SSL-stripping man-in-the-middle attacks. The SSL-stripping attack works by transparently converting a secure HTTPS connection into a plain HTTP connection. The user can see that the connection is insecure, but crucially there is no way of knowing whether the connection should be secure. HSTS addresses this problem by informing the browser that connections to the site should always use TLS/SSL. See also RFC 6797.
Custom Headers¶
Sometimes you may need to model a custom header type which is not part of HTTP and still be able to use it as convenient as is possible with the built-in types.
Because of the number of ways one may interact with headers (i.e. try to match a CustomHeader
against a RawHeader
or the other way around etc), a helper trait for custom Header types and their companions classes are provided by Apache Pekko HTTP. Thanks to extending ModeledCustomHeader
instead of the plain CustomHeader
such header can be matched :
sourcefinal class ApiTokenHeader(token: String) extends ModeledCustomHeader[ApiTokenHeader] {
override def renderInRequests = true
override def renderInResponses = true
override val companion = ApiTokenHeader
override def value: String = token
}
object ApiTokenHeader extends ModeledCustomHeaderCompanion[ApiTokenHeader] {
override val name = "apiKey"
override def parse(value: String) = Try(new ApiTokenHeader(value))
}
sourcepublic static class ApiTokenHeader extends ModeledCustomHeader {
ApiTokenHeader(String name, String value) {
super(name, value);
}
public boolean renderInResponses() {
return false;
}
public boolean renderInRequests() {
return false;
}
}
static class ApiTokenHeaderFactory extends ModeledCustomHeaderFactory<ApiTokenHeader> {
public String name() {
return "apiKey";
}
@Override
public ApiTokenHeader parse(String value) {
return new ApiTokenHeader(name(), value);
}
}
Which allows this CustomHeader to be used in the following scenarios:
sourceval ApiTokenHeader(t1) = ApiTokenHeader("token")
t1 should ===("token")
val RawHeader(k2, v2) = ApiTokenHeader("token")
k2 should ===("apiKey")
v2 should ===("token")
// will match, header keys are case insensitive
val ApiTokenHeader(v3) = RawHeader("APIKEY", "token")
v3 should ===("token")
intercept[MatchError] {
// won't match, different header name
val ApiTokenHeader(v4) = DifferentHeader("token")
}
intercept[MatchError] {
// won't match, different header name
val RawHeader("something", v5) = DifferentHeader("token")
}
intercept[MatchError] {
// won't match, different header name
val ApiTokenHeader(v6) = RawHeader("different", "token")
}
sourcefinal ApiTokenHeaderFactory apiTokenHeaderFactory = new ApiTokenHeaderFactory();
final ApiTokenHeader token = apiTokenHeaderFactory.create("token");
assertEquals("token", token.value());
final HttpHeader header = apiTokenHeaderFactory.create("token");
assertEquals("apiKey", header.name());
assertEquals("token", header.value());
final Optional<ApiTokenHeader> fromRaw =
apiTokenHeaderFactory.from(RawHeader.create("apiKey", "token"));
assertTrue("Expected a header", fromRaw.isPresent());
assertEquals("apiKey", fromRaw.get().name());
assertEquals("token", fromRaw.get().value());
// will match, header keys are case insensitive
final Optional<ApiTokenHeader> fromRawUpper =
apiTokenHeaderFactory.from(RawHeader.create("APIKEY", "token"));
assertTrue("Expected a header", fromRawUpper.isPresent());
assertEquals("apiKey", fromRawUpper.get().name());
assertEquals("token", fromRawUpper.get().value());
// won't match, different header name
final Optional<ApiTokenHeader> wrong =
apiTokenHeaderFactory.from(RawHeader.create("different", "token"));
assertFalse(wrong.isPresent());
Including usage within the header directives like in the following headerValuePF example:
sourcedef extractFromCustomHeader = headerValuePF {
case t @ ApiTokenHeader(token) => s"extracted> $t"
case raw: RawHeader => s"raw> $raw"
}
val routes = extractFromCustomHeader { s =>
complete(s)
}
Get().withHeaders(RawHeader("apiKey", "TheKey")) ~> routes ~> check {
status should ===(StatusCodes.OK)
responseAs[String] should ===("extracted> apiKey: TheKey")
}
Get().withHeaders(RawHeader("somethingElse", "TheKey")) ~> routes ~> check {
status should ===(StatusCodes.OK)
responseAs[String] should ===("raw> somethingElse: TheKey")
}
Get().withHeaders(ApiTokenHeader("TheKey")) ~> routes ~> check {
status should ===(StatusCodes.OK)
responseAs[String] should ===("extracted> apiKey: TheKey")
}
sourceimport org.apache.pekko.http.javadsl.server.Directives;
import static org.apache.pekko.http.javadsl.server.Directives.headerValuePF;
final ApiTokenHeaderFactory apiTokenHeaderFactory = new ApiTokenHeaderFactory();
final PartialFunction<HttpHeader, String> extractFromCustomHeader =
new JavaPartialFunction<HttpHeader, String>() {
@Override
public String apply(HttpHeader header, boolean isCheck) throws Exception {
if (isCheck) return null;
return apiTokenHeaderFactory
.from(header)
.map(apiTokenHeader -> "extracted> " + apiTokenHeader)
.orElseGet(() -> "raw> " + header);
}
};
final Route route = headerValuePF(extractFromCustomHeader, Directives::complete);
testRoute(route)
.run(HttpRequest.GET("/").addHeader(RawHeader.create("apiKey", "TheKey")))
.assertStatusCode(StatusCodes.OK)
.assertEntity("extracted> apiKey: TheKey");
testRoute(route)
.run(HttpRequest.GET("/").addHeader(RawHeader.create("somethingElse", "TheKey")))
.assertStatusCode(StatusCodes.OK)
.assertEntity("raw> somethingElse: TheKey");
testRoute(route)
.run(HttpRequest.GET("/").addHeader(apiTokenHeaderFactory.create("TheKey")))
.assertStatusCode(StatusCodes.OK)
.assertEntity("extracted> apiKey: TheKey");
When defining custom headers, it is better to extend ModeledCustomHeader
instead of its parent CustomHeader
. Custom headers that extend ModeledCustomHeader
automatically comply with the pattern matching semantics that usually apply to built-in types (such as matching a custom header against a RawHeader
in routing layers of Apache Pekko HTTP applications).
Attributes¶
Sometimes it can be useful to keep track of some information associated with a request without explicitly closing over it. Such information can be attached to a request or response though message attributes:
sourcecase class User(name: String)
object User {
val attributeKey = AttributeKey[User]("user")
}
def determineUser(req: HttpRequest): HttpRequest = {
val user = // ... somehow determine the user for this request
// Add the attribute
req.addAttribute(User.attributeKey, user)
}
// Retrieve the attribute
val user: Option[User] = requestWithAttribute.attribute(User.attributeKey)
sourceclass User {
final String name;
public User(String name) {
this.name = name;
}
public static final AttributeKey<User> attributeKey = AttributeKey.create("user", User.class);
}
public HttpRequest determineUser(HttpRequest request) {
User user = // ... somehow determine the user for this request
// Add the attribute
return request.addAttribute(User.attributeKey, user);
}
// Retrieve the attribute
Optional<User> user = requestWithAttribute.getAttribute(User.attributeKey);
Message attributes are only to be used within in your application, they are not present on the wire.
Parsing / Rendering¶
Parsing and rendering of HTTP data structures is heavily optimized and for most types there’s currently no public API provided to parse (or render to) Strings or byte arrays.
Various parsing and rendering settings are available to tweak in the configuration under pekko.http.client[.parsing]
, pekko.http.server[.parsing]
and pekko.http.host-connection-pool[.client.parsing]
, with defaults for all of these being defined in the pekko.http.parsing
configuration section.
For example, if you want to change a parsing setting for all components, you can set the pekko.http.parsing.illegal-header-warnings = off
value. However this setting can be still overridden by the more specific sections, like for example pekko.http.server.parsing.illegal-header-warnings = on
.
In this case both client
and host-connection-pool
APIs will see the setting off
, however the server will see on
.
In the case of pekko.http.host-connection-pool.client
settings, they default to settings set in pekko.http.client
, and can override them if needed. This is useful, since both client
and host-connection-pool
APIs, such as the Client API Http().outgoingConnection
or the Host Connection Pool APIs Http().singleRequest
or Http().superPool
, usually need the same settings, however the server
most likely has a very different set of settings.
Registering Custom Media Types¶
Apache Pekko HTTP predefines
most commonly encountered media types and emits them in their well-typed form while parsing http messages. Sometimes you may want to define a custom media type and inform the parser infrastructure about how to handle these custom media types, e.g. that application/custom
is to be treated as NonBinary
with WithFixedCharset
. To achieve this you need to register the custom media type in the server’s settings by configuring ParserSettings
like this:
source
// similarly in Java: `org.apache.pekko.http.javadsl.settings.[...]`
import org.apache.pekko
import pekko.http.scaladsl.settings.ParserSettings
import pekko.http.scaladsl.settings.ServerSettings
// define custom media type:
val utf8 = HttpCharsets.`UTF-8`
val `application/custom`: WithFixedCharset =
MediaType.customWithFixedCharset("application", "custom", utf8)
// add custom media type to parser settings:
val parserSettings = ParserSettings.forServer(system).withCustomMediaTypes(`application/custom`)
val serverSettings = ServerSettings(system).withParserSettings(parserSettings)
val routes = extractRequest { r =>
complete(r.entity.contentType.toString + " = " + r.entity.contentType.getClass)
}
val binding = Http().newServerAt("localhost", 0).withSettings(serverSettings).bind(routes)
sourceimport static org.apache.pekko.http.javadsl.server.Directives.complete;
import static org.apache.pekko.http.javadsl.server.Directives.extractRequest;
// Define custom media type:
final MediaType.WithFixedCharset applicationCustom =
MediaTypes.customWithFixedCharset(
"application",
"custom", // The new Media Type name
HttpCharsets.UTF_8, // The charset used
new HashMap<>(), // Empty parameters
false); // No arbitrary subtypes are allowed
// Add custom media type to parser settings:
final ParserSettings parserSettings =
ParserSettings.forServer(system).withCustomMediaTypes(applicationCustom);
final ServerSettings serverSettings =
ServerSettings.create(system).withParserSettings(parserSettings);
final Route route =
extractRequest(
req ->
complete(
req.entity().getContentType().toString()
+ " = "
+ req.entity().getContentType().getClass()));
final CompletionStage<ServerBinding> binding =
Http.get(system).newServerAt(host, 0).withSettings(serverSettings).bind(route);
You may also want to read about MediaType Registration trees, in order to register your vendor specific media types in the right style / place.
Registering Custom Status Codes¶
Similarly to media types, Apache Pekko HTTP predefines
well-known status codes, however sometimes you may need to use a custom one (or are forced to use an API which returns custom status codes). Similarly to the media types registration, you can register custom status codes by configuring ParserSettings
like this:
source// similarly in Java: `org.apache.pekko.http.javadsl.settings.[...]`
import org.apache.pekko.http.scaladsl.settings.{ ParserSettings, ServerSettings }
// define custom status code:
val LeetCode = StatusCodes.custom(777, "LeetCode", "Some reason", isSuccess = true, allowsEntity = false)
// add custom method to parser settings:
val parserSettings = ParserSettings.forServer(system).withCustomStatusCodes(LeetCode)
val serverSettings = ServerSettings(system).withParserSettings(parserSettings)
val clientConSettings = ClientConnectionSettings(system).withParserSettings(parserSettings)
val clientSettings = ConnectionPoolSettings(system).withConnectionSettings(clientConSettings)
val routes =
complete(HttpResponse(status = LeetCode))
// use serverSettings in server:
val binding = Http().newServerAt("127.0.0.1", 0).withSettings(serverSettings).bind(routes).futureValue
// use clientSettings in client:
val request = HttpRequest(uri = s"http://127.0.0.1:${binding.localAddress.getPort}/")
val response = Http().singleRequest(request, settings = clientSettings)
// futureValue is a ScalaTest helper:
response.futureValue.status should ===(LeetCode)
sourceimport static org.apache.pekko.http.javadsl.server.Directives.complete;
import static org.apache.pekko.http.javadsl.server.Directives.extractRequest;
// Define custom status code:
final StatusCode leetCode =
StatusCodes.custom(
777, // Our custom status code
"LeetCode", // Our custom reason
"Some reason", // Our custom default message
true, // It should be considered a success response
false); // Does not allow entities
// Add custom method to parser settings:
final ParserSettings parserSettings =
ParserSettings.forServer(system).withCustomStatusCodes(leetCode);
final ServerSettings serverSettings =
ServerSettings.create(system).withParserSettings(parserSettings);
final ClientConnectionSettings clientConSettings =
ClientConnectionSettings.create(system).withParserSettings(parserSettings);
final ConnectionPoolSettings clientSettings =
ConnectionPoolSettings.create(system).withConnectionSettings(clientConSettings);
final Route route = extractRequest(req -> complete(HttpResponse.create().withStatus(leetCode)));
// Use serverSettings in server:
final CompletionStage<ServerBinding> binding =
Http.get(system).newServerAt(host, 0).withSettings(serverSettings).bind(route);
final ServerBinding serverBinding = binding.toCompletableFuture().get();
final int port = serverBinding.localAddress().getPort();
// Use clientSettings in client:
final HttpResponse response =
Http.get(system)
.singleRequest(
HttpRequest.GET("http://" + host + ":" + port + "/"),
ConnectionContext.https(SSLContext.getDefault()),
clientSettings,
system.log())
.toCompletableFuture()
.get();
// Check we get the right code back
assertEquals(leetCode, response.status());
Registering Custom HTTP Method¶
Apache Pekko HTTP also allows you to define custom HTTP methods, other than the well-known methods predefined
in Apache Pekko HTTP. To use a custom HTTP method, you need to define it, and then add it to parser settings like below:
sourceimport org.apache.pekko.http.scaladsl.settings.{ ParserSettings, ServerSettings }
// define custom method type:
val BOLT = HttpMethod.custom("BOLT", safe = false,
idempotent = true, requestEntityAcceptance = Expected)
// add custom method to parser settings:
val parserSettings = ParserSettings.forServer(system).withCustomMethods(BOLT)
val serverSettings = ServerSettings(system).withParserSettings(parserSettings)
val routes = extractMethod { method =>
complete(s"This is a ${method.name} method request.")
}
val binding = Http().newServerAt(host, port).withSettings(serverSettings).bind(routes)
val request = HttpRequest(BOLT, s"http://$host:$port/", protocol = `HTTP/1.1`)
sourceimport static org.apache.pekko.http.javadsl.server.Directives.complete;
import static org.apache.pekko.http.javadsl.server.Directives.extractMethod;
// define custom method type:
HttpMethod BOLT = HttpMethods.custom("BOLT", false, true, Expected);
// add custom method to parser settings:
final ParserSettings parserSettings = ParserSettings.forServer(system).withCustomMethods(BOLT);
final ServerSettings serverSettings =
ServerSettings.create(system).withParserSettings(parserSettings);
final Route routes =
concat(extractMethod(method -> complete("This is a " + method.name() + " request.")));
final Http http = Http.get(system);
final CompletionStage<ServerBinding> binding =
http.newServerAt(host, port)
.withSettings(serverSettings)
.logTo(loggingAdapter)
.bind(routes);
HttpRequest request =
HttpRequest.create()
.withUri("http://" + host + ":" + Integer.toString(port))
.withMethod(BOLT)
.withProtocol(HTTP_1_1);
CompletionStage<HttpResponse> response = http.singleRequest(request);