Wt  4.0.2
Classes | Public Member Functions | Static Public Member Functions | List of all members
Wt::Http::Client Class Reference

An HTTP client. More...

#include <Wt/Http/Client.h>

Inheritance diagram for Wt::Http::Client:
Inheritance graph
[legend]

Classes

struct  URL
 Utility class representing an URL. More...
 

Public Member Functions

 Client ()
 Default constructor. More...
 
 Client (Wt::AsioWrapper::asio::io_service &ioService)
 Constructor. More...
 
virtual ~Client ()
 Destructor. More...
 
void setTimeout (std::chrono::steady_clock::duration timeout)
 Sets an I/O timeout. More...
 
std::chrono::steady_clock::duration timeout () const
 Returns the I/O timeout. More...
 
void setMaximumResponseSize (std::size_t bytes)
 Sets a maximum response size. More...
 
std::size_t maximumResponseSize () const
 Returns the maximum response size. More...
 
void setSslCertificateVerificationEnabled (bool enabled)
 Enables SSL certificate verification. More...
 
bool isSslCertificateVerificationEnabled () const
 Returns whether SSL certificate verification is enabled. More...
 
void setSslVerifyFile (const std::string &verifyFile)
 Sets a SSL certificate used for server identity verification. More...
 
void setSslVerifyPath (const std::string &verifyPath)
 Sets a path with SSL certificates for server identity verification. More...
 
bool get (const std::string &url)
 Starts a GET request. More...
 
bool get (const std::string &url, const std::vector< Message::Header > headers)
 Starts a GET request. More...
 
bool post (const std::string &url, const Message &message)
 Starts a POST request. More...
 
bool put (const std::string &url, const Message &message)
 Starts a PUT request. More...
 
bool deleteRequest (const std::string &url, const Message &message)
 Starts a DELETE request. More...
 
bool patch (const std::string &url, const Message &message)
 Starts a PATCH request. More...
 
bool request (Http::Method method, const std::string &url, const Message &message)
 Starts a request. More...
 
void abort ()
 Aborts the curent request. More...
 
Signal< Wt::AsioWrapper::error_code, Message > & done ()
 Signal that is emitted when the current request is done. More...
 
Signal< Message > & headersReceived ()
 Signal that is emitted when all response headers have been received. More...
 
Signal< std::string > & bodyDataReceived ()
 Signal that is emitted when more body data was received. More...
 
bool followRedirect () const
 Returns whether the client will follow redirects. More...
 
void setFollowRedirect (bool followRedirect)
 Set whether the client will follow redirects. More...
 
int maxRedirects () const
 Returns the maximum number of redirects to follow. More...
 
void setMaxRedirects (int maxRedirects)
 Set the maximum number of redirects to follow. More...
 
- Public Member Functions inherited from Wt::WObject
void addChild (std::unique_ptr< WObject > child)
 Add a child WObject whose lifetime is determined by this WObject.
 
template<typename Child >
Child * addChild (std::unique_ptr< Child > child)
 Add a child WObject, returning a raw pointer. More...
 
std::unique_ptr< WObjectremoveChild (WObject *child)
 Remove a child WObject, so its lifetime is no longer determined by this WObject.
 
virtual const std::string id () const
 Returns the (unique) identifier for this object. More...
 
virtual void setObjectName (const std::string &name)
 Sets an object name. More...
 
virtual std::string objectName () const
 Returns the object name. More...
 
void resetLearnedSlots ()
 Resets learned stateless slot implementations. More...
 
template<class T >
void resetLearnedSlot (void(T::*method)())
 Resets a learned stateless slot implementation. More...
 
template<class T >
WStatelessSlot * implementStateless (void(T::*method)())
 Declares a slot to be stateless and learn client-side behaviour on first invocation. More...
 
template<class T >
WStatelessSlot * implementStateless (void(T::*method)(), void(T::*undoMethod)())
 Declares a slot to be stateless and learn client-side behaviour in advance. More...
 
void isNotStateless ()
 Marks the current function as not stateless. More...
 
template<class T >
WStatelessSlot * implementJavaScript (void(T::*method)(), const std::string &jsCode)
 Provides a JavaScript implementation for a method. More...
 
- Public Member Functions inherited from Wt::Core::observable
 observable () noexcept
 Default constructor.
 
virtual ~observable ()
 Destructor. More...
 

Static Public Member Functions

static bool parseUrl (const std::string &url, URL &parsedUrl)
 Utility method to parse a URL. More...
 

Additional Inherited Members

- Public Types inherited from Wt::WObject
typedef void(WObject::* Method) ()
 Typedef for a WObject method without arguments.
 
- Protected Member Functions inherited from Wt::WObject
virtual WStatelessSlot * getStateless (Method method)
 On-demand stateless slot implementation. More...
 

Detailed Description

An HTTP client.

This class implements an HTTP client. It can be used to interact with web services using the HTTP protocol.

The client uses asynchronous I/O and only provides an asynchronous interface: you cannot actively wait for an operation to complete, instead the client will notify you of the result using the done() signal.

Because the client uses asynchronous I/O, it does its work within the scope of an event-driven thread pool implementation. By default, this is the same thread pool that is used by the Wt server, available through WServer::ioService(), but you may also use the client by providing it an explicit I/O service to be used.

The client supports the HTTP and HTTPS (if Wt was built with OpenSSL support) protocols, and can be used for GET and POST methods. One client can do only one operation at a time.

Usage example:

...
auto client = addChild(std::make_unique<Http::Client>());
client->setTimeout(std::chrono::seconds{15});
client->setMaximumResponseSize(10 * 1024);
client->done().connect(std::bind(&MyWidget::handleHttpResponse, this, _1, _2));
if (client->get("http://www.webtoolkit.eu/wt/blog/feed/"))
else {
// in case of an error in the %URL
}
}
void handleHttpResponse(std::system::error_code err, const Http::Message& response)
{
if (!err && response.status() == 200) {
... parse response.body()
}
}

The function connected to the done() signal will be run within the context of the application that created the client. WServer::post() is used for this.

Basic access authentication

When you want to add authentication information in the URL, this can be done as https://username:password@www.example.com/. When doing this, make sure that the username and password string are URL-encoded (Wt::Utils::urlEncode). For example, https://username:pass word@.nosp@m.www..nosp@m.examp.nosp@m.le.c.nosp@m.om/ should be passed as https://username:pass%20word@www.example.com/.

Constructor & Destructor Documentation

Wt::Http::Client::Client ( )

Default constructor.

The client uses the I/O service and thread-pool from the current WApplication::instance().

Wt::Http::Client::Client ( Wt::AsioWrapper::asio::io_service &  ioService)

Constructor.

The client uses the given I/O service and thread-pool, and is useful to use the client outside the context of a web application.

Wt::Http::Client::~Client ( )
virtual

Destructor.

If the client is still busy, the current request is aborted.

See also
abort()

Member Function Documentation

void Wt::Http::Client::abort ( )

Aborts the curent request.

If the client is currently busy, this cancels the pending request. done() will be emitted with asio::error::operation_aborted.

Note
The abort will be performed asynchronously, so it is possible that done() is still emitted with a successful response after abort() is called.
Signal<std::string>& Wt::Http::Client::bodyDataReceived ( )

Signal that is emitted when more body data was received.

The signal contains the next body data chunk received. You may want to catch this signal if you want to process the response as it is being received.

You may want to use this in combination with setMaximumResponseSize(0) to handle very long responses.

bool Wt::Http::Client::deleteRequest ( const std::string &  url,
const Message message 
)

Starts a DELETE request.

The function starts an asynchronous DELETE request, and returns immediately.

The function returns true when the DELETE request has been scheduled, and thus done() will be emitted eventually.

The function returns false if the client could not schedule the request, for example if the url is invalid or if the URL scheme is not supported.

See also
request(), done()
Signal<Wt::AsioWrapper::error_code, Message>& Wt::Http::Client::done ( )

Signal that is emitted when the current request is done.

The error is 0 if the HTTP request was successful. Then, the message contains the result.

If the error is not 0, then an error message is given by err.message().

Typical code to process the result is:

void handle(Wt::AsioWrapper::error_code err, const Http::Message& response)
{
if (!err) {
if (response.status() == 200) {
... success
}
} else {
Wt::log("error") << "Http::Client error: " << err.message();
}
}
bool Wt::Http::Client::followRedirect ( ) const

Returns whether the client will follow redirects.

See also
setFollowRedirect
bool Wt::Http::Client::get ( const std::string &  url)

Starts a GET request.

The function starts an asynchronous GET request, and returns immediately.

The function returns true when the GET request has been scheduled, and thus done() will be emitted eventually.

The function returns false if the client could not schedule the request, for example if the url is invalid or if the URL scheme is not supported.

See also
request(), done()
bool Wt::Http::Client::get ( const std::string &  url,
const std::vector< Message::Header headers 
)

Starts a GET request.

The function starts an asynchronous GET request, and returns immediately.

The function returns true when the GET request has been scheduled, and thus done() will be emitted eventually.

The function returns false if the client could not schedule the request, for example if the url is invalid or if the URL scheme is not supported.

This function accepts one or more headers.

See also
request(), done()
Signal<Message>& Wt::Http::Client::headersReceived ( )

Signal that is emitted when all response headers have been received.

The signal forwards the message with all headers, but with empty body text. You may want to catch this signal if you want to examine the headers prior to having received the complete message.

See also
done(), bodyDataReceived()
bool Wt::Http::Client::isSslCertificateVerificationEnabled ( ) const

Returns whether SSL certificate verification is enabled.

See also
setSslCertificateVerificationEnabled()
std::size_t Wt::Http::Client::maximumResponseSize ( ) const

Returns the maximum response size.

See also
setMaximumResponseSize()
int Wt::Http::Client::maxRedirects ( ) const

Returns the maximum number of redirects to follow.

See also
setMaxRedirects()
bool Wt::Http::Client::parseUrl ( const std::string &  url,
URL parsedUrl 
)
static

Utility method to parse a URL.

This parses a URL into an URL object.

The method returns true if the URL could be parsed successfully.

bool Wt::Http::Client::patch ( const std::string &  url,
const Message message 
)

Starts a PATCH request.

The function starts an asynchronous PATCH request, and returns immediately.

The function returns true when the PATCH request has been scheduled, and thus done() will be emitted eventually.

The function returns false if the client could not schedule the request, for example if the url is invalid or if the URL scheme is not supported.

See also
request(), done()
bool Wt::Http::Client::post ( const std::string &  url,
const Message message 
)

Starts a POST request.

The function starts an asynchronous POST request, and returns immediately.

The function returns true when the POST request has been scheduled, and thus done() will be emitted eventually.

The function returns false if the client could not schedule the request, for example if the url is invalid or if the URL scheme is not supported.

See also
request(), done()
bool Wt::Http::Client::put ( const std::string &  url,
const Message message 
)

Starts a PUT request.

The function starts an asynchronous PUT request, and returns immediately.

The function returns true when the PUT request has been scheduled, and thus done() will be emitted eventually.

The function returns false if the client could not schedule the request, for example if the url is invalid or if the URL scheme is not supported.

See also
request(), done()
bool Wt::Http::Client::request ( Http::Method  method,
const std::string &  url,
const Message message 
)

Starts a request.

The function starts an asynchronous HTTP request, and returns immediately.

The function returns true when the request has been scheduled, and thus done() will be emitted eventually.

The function returns false if the client could not schedule the request, for example if the url is invalid or if the URL scheme is not supported.

See also
request(), done()
void Wt::Http::Client::setFollowRedirect ( bool  followRedirect)

Set whether the client will follow redirects.

If set and the request method is GET, redirects are automatically followed.

void Wt::Http::Client::setMaximumResponseSize ( std::size_t  bytes)

Sets a maximum response size.

The response is stored in-memory. To avoid a DoS by a malicious downstream HTTP server, the response size is bounded by an upper limit.

The limit includes status line, headers and response body.

The default value is 64 kilo bytes.

A value of 0 has a special meaning: the size of the response will not be limited, but the response body will not be stored in the response message. Instead the data is made available only to bodyDataReceived() to be processed incrementally.

void Wt::Http::Client::setMaxRedirects ( int  maxRedirects)

Set the maximum number of redirects to follow.

This is used only when followRedirect() is enabled.

The default is 20.

void Wt::Http::Client::setSslCertificateVerificationEnabled ( bool  enabled)

Enables SSL certificate verification.

For https requests, it is (very strongly!) recommended to perform certificate verification: this verifies that you are indeed connected to the server you intended (and not to a man-in-the-middle). Without such a check, encryption simply isn't very useful.

Nevertheless, there may be situations in which you will want to disable this functionality.

The default configuration is to have certificate verification enabled.

void Wt::Http::Client::setSslVerifyFile ( const std::string &  verifyFile)

Sets a SSL certificate used for server identity verification.

This setting only affects a https request: it configures a certificate file to be used to verify the identity of the server.

Note
Certificate verification does not work reliably yet.
void Wt::Http::Client::setSslVerifyPath ( const std::string &  verifyPath)

Sets a path with SSL certificates for server identity verification.

This setting only affects a https request: it configures a directory containing certificates to be used to verify the identity of the server.

Note
Certificate verification does not work reliably yet.
void Wt::Http::Client::setTimeout ( std::chrono::steady_clock::duration  timeout)

Sets an I/O timeout.

This sets a timeout waiting for I/O operations. The timeout does not bound the total timeout, since the timer is reset on each I/O progress.

The default timeout is 10 seconds.

std::chrono::steady_clock::duration Wt::Http::Client::timeout ( ) const

Returns the I/O timeout.

See also
setTimeout()

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