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URL and HTTP Communication

In the Java programming language, Java developers can access APIs to communicate directly with web resources using URLs and HTTP (Internet web addresses and web protocols). These web-based communication protocols allow Web API applications to connect directly to web servers, send necessary web requests, and receive responses to send requests.

Today, the main API for modern Java application design and development is the java.net.http package or library, which was introduced in Java 11. In Java 8, this was typically performed using the HttpURLConnection method.

URL Java Web Connection Method.

In Internet services, a website webpage URL (Uniform Resource Locator) indicates the digital location of all data information resources on a website on the Internet. A website’s data resources are accessed through URLs.

Example of a simple URL.

https://vcanhelpsu.com/index.html

A typical website URL might look like this.

https://vcanhelpsu.com/contact-us/

↓                   ↓            ↓          ↓

Web Protocol URL Host Webpage

Creating a URL in Java Web.

In older Java 8 versions.

import java.net.*;

URL url =

new URL(“https://vcanhelpsu.com”);

Using this method, Java users can access digital information about a URL.

System.out.println(url.getProtocol());

System.out.println(url.getHost());

System.out.println(url.getPath());

Possible output.

https

vcanhelpsu.com

Common Java Used URL Methods

HTTP Protocol Communication in Java Internet.

HTTP (Hypertext Transfer Protocol) is an important web protocol used in the internet world to exchange digital data, information, and other web resources or establish communication between a client and a web server.

Basic HTTP Protocol Communication Java Flow.

Client Web Request

            |

| HTTP Request

           ↓

Dedicated Host or Web Server

           |

| HTTP Response to Client

          ↓

Client Receive Request

HTTP Protocol Example.

GET /users/10 HTTP/1.1

To this client HTTP request, the web server can respond as follows:

HTTP/1.1 200 OK

And can return web resource data values ​​like JSON or HTML as output.

HttpURLConnection concept in Java 8.

In Java 8, the HTTP protocol typically uses the HttpURLConnection method to access web resources.

Example of the GET Java request method.

import java.net.*;

import java.io.*;

public class Main {

public static void main(String[] args) {

HttpURLConnection connection = null;

try {

URL url = new URL(“https://vcanhelpsu.com/”);

connection = (HttpURLConnection) url.openConnection();

connection.setRequestMethod(“GET”);

connection.setConnectTimeout(10000);

connection.setReadTimeout(10000);

connection.setRequestProperty(“User-Agent”, “Mozilla/5.0”);

int status = connection.getResponseCode();

System.out.println(“What is Status -: ” + status);

InputStream stream;

if (status >= 200 && status < 400) {

stream = connection.getInputStream();

} else {

stream = connection.getErrorStream();

}

if (stream != null) {

try (BufferedReader reader =

new BufferedReader(

new InputStreamReader(stream)) {

string line;

while ((line = reader.readLine()) != null) {

System.out.println(line);

}

}

}

} catch (Exception ex) {

System.out.println(“Display Error -: ” + ex.getMessage());

} finally {

if (connection != null) {

connection.disconnect();

}

}

}

}

Its output.

HTTP Status Code -: 200

HTTP Status Message -: OK

<!DOCTYPE html>

<html>

…

</html>

Common Java HTTP methods.

In the Java programming language, the following are some popular HTTP web protocol request methods used to retrieve access to Internet web resources.

HTTP Used Java Web Request Methods

Example of an important HTTP web request method.

connection.setRequestMethod(“GET”);

                   or

connection.setRequestMethod(“POST”);

Sending a POST request using the Java Web HTTP Protocol.

In online Internet communication, an HTTP POST request allows data to be sent from the client side to a dedicated web server or host.

URL url =

new URL(“https://vcanhelpsu.com//api”);

HttpURLConnection connection =

(HttpURLConnection) url.openConnection();

Example of the POST Java request method.

import java.net.*;

import java.io.*;

import java.nio.charset.StandardCharsets;

public class Main {

public static void main(String[] args) {

HttpURLConnection connection = null;

try {

URL url = new URL(“https://vcanhelpsu.com/”);

connection = (HttpURLConnection) url.openConnection();

//here we create a POST request method

connection.setRequestMethod(“POST”);

connection.setDoOutput(true);

connection.setConnectTimeout(10000);

connection.setReadTimeout(10000);

// here we define JSON header

connection.setRequestProperty(

“Content-Type”,

“application/json; charset=UTF-8”

);

connection.setRequestProperty(

“Accept”,

“application/json”

);

// here we read data in JSON data format

String data = “{\”emp_name\”-:\”Siddhi\”}”;

// here we send POST data to connection

try (OutputStream output = connection.getOutputStream()) {

output.write(data.getBytes(StandardCharsets.UTF_8));

}

//here we get response status

int status = connection.getResponseCode();

System.out.println(“HTTP Status is -: ” + status);

System.out.println(

“Response Message is -: ” + connection.getResponseMessage()

);

// here we Read server response

InputStream stream;

if (status >= 200 && status < 400) {

stream = connection.getInputStream();

} else {

stream = connection.getErrorStream();

}

if (stream != null) {

try (BufferedReader reader =

new BufferedReader(

new InputStreamReader(

stream,StandardCharsets.UTF_8

))) {

string line;

while ((line = reader.readLine()) != null) {

System.out.println(line);

}

}

}

} catch (Exception ex) {

System.out.println(

“Display Error -: ” + ex.getMessage()

);

} finally {

if (connection != null) {

connection.disconnect();

}

}

}

}

Its output.

json

{

“emp_name”-: “Siddhi”

}

This setting is required in the posted example.

connection.setDoOutput(true);

This allows the web application to send data in the https request body.

HTTP status code explanation in Java web URL.

Each time an online or offline client-server receives a web-based or specific port-based communication request, a status code is displayed in the output, indicating the result of the web request sent to the client-side web browser.

Commonly used Java HTTP request status codes.

• 200 → OK Request
• 201 → Created Request
• 400 → Bad Request
• 401 → Unauthorized Request
• 403 → Forbidden Request
• 404 → Not Found Request
• 500 → Internal Server Error Issues

Java users can find this in their program terminal web browser as follows.

int status =

connection.getResponseCode();

HTTP header request in Java web concept.

Web headers in Java internet web requests provide additional digital information about the HTTP request or response.

Example of an HTTP header request.

connection.setRequestProperty(

“Accept”,

“application/json”

);

Another HTTP header web request example.

connection.setRequestProperty(

“User-Agent”,

“TestJavaApplication”

);

HttpClient request method in Java 11.

Java 11 introduced the modern HTTP client API web request method for java.net.http.

This is generally a simpler and clearer request method than HttpURLConnection.

A simple GET request method example in Java 11.

import java.net.URI;

import java.net.http.*;

public class Main {

public static void main(String[] args) {

try {

// Here we create an HTTP Client request

HttpClient client = HttpClient.newHttpClient();

// Here we create an HTTP GET request method

HttpRequest request = HttpRequest.newBuilder()

.uri(URI.create(“https://vcanhelpsu.com/”))

.GET()

.build();

// here we send HTTP Request

HttpResponse<String> response = client.send(

request,

HttpResponse.BodyHandlers.ofString()

);

// here it displays HTTP Status Code

System.out.println(

“HTTP Status Code is -: ” + response.statusCode()

);

// here it displays HTTP Response Body

System.out.println(“Website Response is -:”);

System.out.println(response.body());

} catch (Exception ex) {

System.out.println(

“Display Web Request Error -: ” + ex.getMessage()

);

}

}

}

Its output.

HTTP Status Code -: 200

Website Response -:

<!DOCTYPE html>

<html>

<head>

<title>…</title>

…

</html>

A simple GET request flow method explanation.

HttpClient Request

           ↓

HttpRequest Method

          ↓

HTTP GET Method

          ↓

Dedicated Web Server

          ↓

HttpResponse Code

          ↓

statusCode() + body()

GET request example.

response.statusCode();

response.body();

Use this method to retrieve the Java user response status and your content.

Java’s modern HTTP’s URL vs. URI concept.

Modern versions of the Java programming language today use HTTP APIs and URIs as request methods.

URI uri =

URI.create(“https://vcanhelpsu.com//users”);

A functional difference between URLs and URIs.

• URI → This protocol identifies a webpage resource in the online World Wide Web system.
• URL → A URL identifies a website address resource online and provides a method to access it in a client-side web browser.

For modern Java HTTP web communication, the URI method is commonly used with HttpRequest.

Java 8 Version Httpurlconnection Vs Java 11 Version Httpclient Http Request

Simple URL and HTTP Communication Flow.

URL/URI Web Methods

            ↓

HTTP Web Request

           ↓

Dedicated Web Server

           ↓

HTTP Response

           ↓

Status Code + Header + Body Output

This will provide Java developers with improved responses and allow Java users to upload files, images, and many other web resources to the server.

Conclusion of URL and HTTP Communication with Java.

• In a Java web request, a URL indicates the location of a webpage (website address) resource on the digital World Wide Web.
• The HTTP protocol indicates direct communication between a client and a server in a web request.
• In Java 8 versions, the HttpURLConnection method is commonly used.
• In modern Java 11 versions, new web request methods have been included: HttpClient, HttpRequest, and HttpResponse.
• Typical Java client-server communication HTTP requests mainly use GET, POST, PUT, PATCH, and DELETE request methods.
• In Java web communication, the HTTP response contains a status code, headers, and body.