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Table of Contents
The Jetty HTTP client module provides easy-to-use APIs and utility classes to perform HTTP (or HTTPS) requests.
Jetty’s HTTP client is non-blocking and asynchronous. It offers an asynchronous API that never blocks for I/O, making it very efficient in thread utilization and well suited for high performance scenarios such as load testing or parallel computation.
However, when all you need to do is to perform a
GET request to a resource, Jetty’s HTTP client offers also a synchronous API; a programming interface
where the thread that issued the request blocks until the request/response conversation is complete.
Jetty’s HTTP client supports different transports: HTTP/1.1, FastCGI and HTTP/2.
This means that the semantic of a HTTP request (that is, "
GET me the resource
/index.html ") can be carried over the network in different formats.
The most common and default format is HTTP/1.1.
That said, Jetty’s HTTP client can carry the same request using the FastCGI format or the new HTTP/2 format.
The FastCGI transport is heavily used in Jetty’s FastCGI support that allows Jetty to work as a reverse proxy to PHP (exactly like Apache or Nginx do) and therefore be able to serve - for example - WordPress websites.
The HTTP/2 transport allows Jetty’s HTTP client to perform requests using HTTP/2 to HTTP/2 enabled web sites, see also Jetty’s HTTP/2 support.
Out of the box features that you get with the Jetty HTTP client include:
The main class is named
You can think of a
HttpClient instance as a browser instance.
Like a browser it can make requests to different domains, it manages redirects, cookies and authentication, you can configure it with a proxy, and
it provides you with the responses to the requests you make.
In order to use
HttpClient, you must instantiate it, configure it, and then start it:
// Instantiate HttpClient HttpClient httpClient = new HttpClient(); // Configure HttpClient, for example: httpClient.setFollowRedirects(false); // Start HttpClient httpClient.start();
You may create multiple instances of
HttpClient, but typically one instance is enough for an application.
There are several reasons for having multiple
HttpClient instances including, but not limited to:
When you create a
HttpClient instance using the parameterless constructor, you will only be able to perform plain HTTP requests and you will not be able to perform HTTPS requests.
In order to perform HTTPS requests, you should create first a
SslContextFactory.Client, configure it, and pass it to the
When created with a
HttpClient will be able to perform both HTTP and HTTPS requests to any domain.
// Instantiate and configure the SslContextFactory SslContextFactory.Client sslContextFactory = new SslContextFactory.Client(); // Instantiate HttpClient with the SslContextFactory HttpClient httpClient = new HttpClient(sslContextFactory); // Configure HttpClient, for example: httpClient.setFollowRedirects(false); // Start HttpClient httpClient.start();
It is recommended that when your application stops, you also stop the
HttpClient instance (or instances) that you are using.
HttpClient makes sure that the memory it holds (for example, authentication credentials, cookies, etc.) is released, and that the thread pool and scheduler are properly stopped allowing all threads used by
HttpClient to exit.