What does an HTTP request consist of?

An HTTP request consists of several main parts:

1. Request Line — contains the request method (GET, POST, PUT, etc.), URI (resource address), and HTTP protocol version.

   Example: GET /index.html HTTP/1.1

2. Headers — a set of key-value pairs that convey additional information about the request, such as content type, language, cookies, authorization, etc.

   Example:

   Host: example.com
   User-Agent: Mozilla/5.0
   Accept: text/html
   

3. Empty line — separates headers from the body of the request.

4. Request Body — an optional part used to send data to the server, for example, in POST or PUT requests.

In Java, classes from the java.net package or libraries like Apache HttpClient are often used to work with HTTP requests, where these parts are represented by corresponding methods and objects.