HttpURLConnection Class in java

The Java HttpURLConnection class is http specific URLConnection. It works for HTTP protocol only.

  HttpURLConnection is a subclass of URLConnection which provides support for HTTP connections.


How to get the object of HttpURLConnection class

We can obtain an HttpURLConnection in the same way by calling openConnection( ) on a URL object, but we must type cast the result to HttpURLConnection .


URL url=new URL("https://www.onlyjavatech.com/HttpURLConnection-Class-in-Java");    
HttpURLConnection ob=(HttpURLConnection)url.openConnection()

Example of HttpURLConnection

Example of getting header information of any url.

import java.io.*;    
import java.net.*;    
public class Example{    
public static void main(String[] args){    
try{    
URL url=new URL("https://www.google.co.in");    
HttpURLConnection ob=(HttpURLConnection)url.openConnection();  
for(int i=1;i<=9;i++){  
System.out.println(ob.getHeaderFieldKey(i)+" = "+ob.getHeaderField(i));  
}  
ob.disconnect();   
}catch(Exception e){
e.printStackTrace();
;
}    
}    
}    

output :

Program of Printing the header fields of URL using Map Interface of Collection Framework.


import java.io.*;
import java.net.*;
import java.util.*;

class Example{
	public static void main(String[] args) throws Exception {
		System.out.println("Enter url :");
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String str = br.readLine();
		HttpURLConnection con = (HttpURLConnection) new URL(str).openConnection();
		Map> map = con.getHeaderFields();
		Set>> itr = map.entrySet();
		for (Map.Entry> x : itr) {
			String key = x.getKey();
			List values = x.getValue();
			System.out.print(key + "\t");
			for (String y : values) {
				System.out.print(y);
			}
			System.out.println();
		}
	}
}

The URI Class

The URI class encapsulates a Uniform Resource Identifier (URI). URIs are similar to URLs.
In fact, URLs constitute a subset of URIs. A URI represents a standard way to identify a resource. A URL also describes how to access the resource.

Cookies

The java.net package includes classes and interfaces that help manage cookies and can be used to create a stateful (as opposed to stateless) HTTP session. The classes are CookieHandler, CookieManager, and HttpCookie.