Fuel
The core package for Fuel
. The documentation outlined here touches most subjects and functions but is not exhaustive.
Installation
You can download and install Fuel
with Maven
and Gradle
. The core package has the following dependencies:
Usage
Making Requests
You can make requests using functions on Fuel
, a FuelManager
instance or the string extensions.
The extensions and functions made available by the core package are listed here:
About PATCH
requests
PATCH
requestsThe default client
is HttpClient
which is a thin wrapper over java.net.HttpUrlConnection
. java.net.HttpUrlConnection
does not support a PATCH
method. HttpClient
converts PATCH
requests to a POST
request and adds a X-HTTP-Method-Override: PATCH
header. While this is a semi-standard industry practice not all APIs are configured to accept this header by default.
Experimental
As of version 1.16.x
you can opt-in to forcing a HTTP Method on the java.net.HttpUrlConnnection
instance using reflection.
About CONNECT
request
CONNECT
requestConnect is not supported by the Java JVM via the regular HTTP clients, and is therefore not supported.
Adding Parameters
Parameters
All the String
extensions listed above, as well as the Fuel
and FuelManager
calls accept a parameter parameters: Parameters
.
URL encoded style for
GET
andDELETE
requestSupport
x-www-form-urlencoded
forPUT
,POST
andPATCH
Parameters
with Body
Parameters
with Body
If a request already has a body, the parameters are url-encoded instead. You can remove the handling of parameter encoding by removing the default ParameterEncoder
request interceptor from your FuelManager
.
Parameters
with multipart/form-data
Parameters
with multipart/form-data
The UploadRequest
handles encoding parameters in the body. Therefore by default, parameter encoding is ignored by ParameterEncoder
if the content type is multipart/form-data
.
Parameters
with empty, array, list or null values
Parameters
with empty, array, list or null valuesAll requests can have parameters, regardless of the method.
a list is encoded as
key[]=value1&key[]=value2&...
an array is encoded as
key[]=value1&key[]=value2&...
an empty string value is encoded as
key
a null value is removed
Adding Request
body
Request
bodyBodies are formed from generic streams, but there are helpers to set it from values that can be turned into streams. It is important to know that, by default, the streams are NOT read into memory until the Request
is sent. However, if you pass in an in-memory value such as a ByteArray
or String
, Fuel
uses RepeatableBody
, which are kept into memory until the Request
is dereferenced.
When you're using the default Client
, bodies are supported for:
POST
PUT
PATCH
(actually aPOST
, as noted above)DELETE
There are several functions to set a Body
for the request. If you are looking for a multipart/form-data
upload request, checkout the UploadRequest
feature.
Use application/json
application/json
If you don't want to set the application/json
header, you can use .jsonBody(value: String)
extension to automatically do this for you.
from String
String
from a File
File
from a InputStream
InputStream
from a lazy
source (InputStream
)
lazy
source (InputStream
)Fuel always reads the body lazily, which means you can also provide a callback that will return a stream. This is also known as a BodyCallback
:
Using automatic body redirection
The default redirection interceptor only forwards RepeatableBody
, and only if the status code is 307 or 308, as per the RFCs. In order to use a RepeatableBody
, pass in a String
or ByteArray
as body, or explicitely set repeatable = true
for the fun body(...)
call.
NOTE this loads the entire body into memory, and therefore is not suited for large bodies.
Adding Headers
Headers
There are many ways to set, overwrite, remove and append headers. For your convenience, internally used and common header names are attached to the Headers
companion and can be accessed (e.g. Headers.CONTENT_TYPE
, Headers.ACCEPT
, ...).
The most common ones are mentioned here:
Reading HeaderValues
HeaderValues
(Over)writing HeaderValues
HeaderValues
Appending HeaderValues
HeaderValues
Note that headers which by the RFC may only have one value are always overwritten, such as Content-Type
.
FuelManager
base headers vs. Request
headers
FuelManager
base headers vs. Request
headersThe baseHeaders
set through a FuelManager
are only applied to a Request
if that request does not have that specific header set yet. There is no appending logic. If you set a header it will overwrite the base value.
Client
headers vs. Request
headers
Client
headers vs. Request
headersAny Client
can add, remove or transform HeaderValues
before it sends the Request
or after it receives the Response
. The default Client
for example sets TE
values.
HeaderValues
values are List
HeaderValues
values are List
Even though some headers can only be set once (and will overwrite even when you try to append), the internal structure is always a list. Before a Request
is made, the default Client
collapses the multiple values, if allowed by the RFCs, into a single header value delimited by a separator for that header. Headers that can only be set once will use the last value by default and ignore earlier set values.
Adding Authentication
Authentication can be added to a Request
using the .authentication()
feature. By default, authentication
is passed on when using the default redirectResponseInterceptor
(which is enabled by default), unless it is redirecting to a different host. You can remove this behaviour by implementing your own redirection logic.
When you call
.authentication()
, a few extra functions are available. If you call a regular function (e.g..header()
) the extra functions are no longer available, but you can safely call.authentication()
again without losing any previous calls.
Basic authentication
Bearer authentication
Any authentication using a header
Adding Progress callbacks
Any request supports Progress
callbacks when uploading or downloading a body; the Connection
header does not support progress (which is the only thing that is sent if there are no bodies). You can have as many progress handlers of each type as you like.
Request progress
Response progress
Throttling progress output
Often the progress of a download will be shown as notification. Since Android Nougat (API 24), only 10 notification updates per second per app are allowed. Anything more than that will result in a log error like E/NotificationService: Package enqueue rate is 10.062265. Shedding events. package=...
.
It is the responsibility of the library user – not of fuel – to remedy this limit. A simple solution could look like this:
Why does totalBytes increase?
Not all source Body
or Response
Body
report their total size. If the size is not known, the current size will be reported. This means that you will constantly get an increasing amount of totalBytes that equals readBytes.
Using multipart/form-data
(UploadRequest
)
multipart/form-data
(UploadRequest
)Fuel supports multipart uploads using the .upload()
feature. You can turn any Request
into a upload request by calling .upload()
or call .upload(method = Method.POST)
directly onto Fuel
/ FuelManager
.
When you call
.upload()
, a few extra functions are available. If you call a regular function (e.g..header()
) the extra functions are no longer available, but you can safely call.upload()
again without losing any previous calls.
DataPart
from File
DataPart
from File
In order to add DataPart
s that are sources from a File
, you can use FileDataPart
, which takes a file: File
. There are some sane defaults for the field name name: String
, and remote file name filename: String
, as well as the Content-Type
and Content-Disposition
fields, but you can override them.
In order to receive a list of files, for example in the field files
, use the array notation:
Sending multiple files in a single datapart is not supported as it's deprecated by the multipart/form-data RFCs, but to simulate this behaviour, give the same name
to multiple parts.
You can use the convenience constructors FileDataPart.from(directory: , filename: , ...args)
to create a FileDataPart
from String
arguments.
DataPart
from inline content
DataPart
from inline contentSometimes you have some content inline that you want to turn into a DataPart
. You can do this with InlineDataPart
:
A filename
is not mandatory and is empty by default; the contentType
is text/plain
by default.
DataPart
from InputStream
(formely Blob
)
DataPart
from InputStream
(formely Blob
)You can also add dataparts from arbitrary InputStream
s, which you can do using BlobDataPart
:
If you don't set the contentLength
to a positive integer, your entire Request
Content-Length
will be undeterminable and the default HttpClient
will switch to chunked streaming mode with an arbitrary stream buffer size.
Multipart request without a file
Simply don't call add
. The parameters are encoded as parts!
Getting a Response
As mentioned before, you can use Fuel
both synchronously and a-synchronously, with support for coroutines.
Blocking responses
By default, there are three response functions to get a request synchronously:
The default charset is UTF-8
. If you want to implement your own deserializers, scroll down to advanced usage.
Async responses
Add a handler to a blocking function, to make it asynchronous:
The default charset is UTF-8
. If you want to implement your own deserializers, scroll down to advanced usage.
Suspended responses
The core package has limited support for coroutines:
When using other packages such as fuel-coroutines
, more response/await functions are available.
Response types
The
ResponseResultOf<U>
type is aTriple
of theRequest
,Response
and aResult<U, FuelError>
The
ResponseOf<U>
type is aTriple
of theRequest
,Response
and aU
; errors are thrownThe
Result<U, FuelError>
type is a non-throwing wrapper aroundU
The
U
type doesn't wrap anything; errors are thrown
Handler types
When defining a handler, you can use one of the following for all responseXXX
functions that accept a Handler
:
This means that you can either choose to unwrap the Result
yourself using a ResultHandler
or ResponseResultHandler
, or define dedicated callbacks in case of success or failure.
Dealing with Result<T, FuelError>
Result<T, FuelError>
Result is a functional style data structure that represents data that contains result of Success or Failure but not both. It represents the result of an action that can be success (with result) or error.
Working with result is easy:
You can call [
fold
] and define a tranformation function for both cases that results in the same return type,[
destructure
] as(data, error) = result
because it is just a data class oruse
when
checking whether it isResult.Success
orResult.Failure
Download response to output (File
or OutputStream
)
File
or OutputStream
)Fuel supports downloading the request Body
to a file using the .download()
feature. You can turn any Request
into a download request by calling .download()
or call .download(method = Method.GET)
directly onto Fuel
/ FuelManager
.
When you call
.download()
, a few extra functions are available. If you call a regular function (e.g..header()
) the extra functions are no longer available, but you can safely call.download()
again without losing any previous calls.
The stream
variant expects your callback to provide a Pair
with both the OutputStream
to write too, as well as a callback that gives an InputStream
, or raises an error.
The
OutputStream
is always closed after the body has been written. Make sure you wrap whatever functionality you need on top of the stream and don't rely on the stream to remain open.The
() -> InputStream
replaces the body after the current body has been written to theOutputStream
. It is used to make sure you can also retrieve the body via theresponse
/await
method results. If you don't want the body to be readable after downloading it, you have to do two things:use an
EmptyDeserializer
withawait(deserializer)
or one of theresponse(deserializer)
variantsprovide an
InputStream
callback thatthrows
or returns an emptyInputStream
.
For downloading larger files it is good to use request.streamDestination { }
instead of request.fileDestination { }
Cancel an async Request
Request
The response
functions called with a handler
are async and return a CancellableRequest
. These requests expose a few extra functions that can be used to control the Future
that should resolve a response:
If you can't get hold of the CancellableRequest
because, for example, you are adding this logic in an Interceptor
, a generic Queue
, or a ProgressCallback
, you can call tryCancel()
which returns true if it was cancelled and false otherwise. At this moment blocking
requests can not be cancelled.
Advanced Configuration
Request Configuration
baseHeaders
is to manage common HTTP header pairs in format ofMap<String, String>
.The base headers are only applied if the request does not have those headers set.
Headers
can be added to a request via various methods including
By default, all subsequent calls overwrite earlier calls, but you may use the
appendHeader
variant to append values to existing values.In earlier versions (1.x.y), a
mapOf
overwrote, andvarargs pair
did not, but this was confusing. In 2.0, this issue has been fixed and improved so it works as expected.
Some of the HTTP headers are defined under
Headers.Companion
and can be used instead of literal strings. This is an encouraged way to configure your header in 2.x.y.
Response Deserialization
Fuel provides built-in support for response deserialization. Here is how one might want to use Fuel together with Gson
There are 4 methods to support response deserialization depending on your needs (also depending on JSON parsing library of your choice), and you are required to implement only one of them.
Another example may be parsing a website that is not UTF-8. By default, Fuel serializes text as UTF-8, we need to define our deserializer as such
Detail Configuration
Use singleton
FuelManager.instance
to manage global configurations.Create separate managers using
FuelManager()
basePath
is used to manage common root path. Great usage is for your static API endpoint.
baseParams
is used to manage commonkey=value
query param, which will be automatically included in all of your subsequent requests in format ofParameters
(Any
is converted toString
bytoString()
method)
client
is a raw HTTP client driver. Generally, it is responsible to makeRequest
intoResponse
. Default isHttpClient
which is a thin wrapper overjava.net.HttpUrlConnection
. You could use any httpClient of your choice by conforming toclient
protocol, and set back toFuelManager.instance
to kick off the effect.keyStore
is configurable by user. By default it isnull
.socketFactory
can be supplied by user. IfkeyStore
is not null,socketFactory
will be derived from it.hostnameVerifier
is configurable by user. By default, it usesHttpsURLConnection.getDefaultHostnameVerifier()
.requestInterceptors
responseInterceptors
is a side-effect to add toRequest
and/orResponse
objects.For example, one might wanna print cUrlString style for every request that hits server in DEBUG mode.
Another example is that you might wanna add data into your Database, you can achieve that with providing
responseInterceptors
such as
Routing Support
In order to organize better your network stack FuelRouting interface allows you to easily setup a Router design pattern.
Last updated