Java Servlets are Java-based components that are used to extend the functionality of web servers and develop dynamic web applications. Servlets are part of the Java Enterprise Edition (Java EE) platform, now known as Jakarta EE, and they are typically used to handle HTTP requests and generate HTTP responses.
Here Are Some Key Points About Java Servlets- Request Handling, Servlets Are Primarily Used
- Request Handling:: Servlets are primarily used to process HTTP requests and generate dynamic content as HTTP responses. They can handle various types of HTTP requests, such as GET, POST, PUT, DELETE, etc.
- Java-based: Servlets are written in Java and follow the Java Servlet API specification. This means that you write your servlet code using Java, which provides platform independence and the ability to run servlets on any server that supports the Servlet API.
- Lifecycle: Servlets have a well-defined lifecycle consisting of initialization, request processing, and destruction phases. Developers can override methods like init(), doGet(), doPost(), and destroy() to customize the behavior of their servlets./li>
- Multithreading: Servlets are multithreaded by nature. Each HTTP request typically spawns a new thread to handle it, allowing multiple requests to be processed concurrently.
- Deployment: Servlets are typically packaged in WAR (Web Application Archive) files and deployed to a servlet container or application server. Popular servlet containers include Apache Tomcat, Jetty, and WildFly.
- MVC Architecture: Servlets are often used as part of the Model-View-Controller (MVC) architecture in web applications. They handle the controller part, processing user input and managing the application’s flow.
- Session Management: Servlets can manage user sessions and store session-related data using the HttpSession object, allowing developers to maintain state between HTTP requests.
- URL Mapping: Servlets are typically mapped to specific URL patterns in the web application’s deployment descriptor (web.xml) or through annotations in modern versions of the Servlet API.
Here's a Simple Example Of Basic Servlet That Responds To GET Request
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/hello")
public class HelloServlet extends HttpServlet
{
protected void doGet(HttpServletRequest request,
HttpServletResponse
response) throws
ServletException, IOException
{
response.setContentType("text/html");
response.getWriter()
.println("<html><body><h1>Hello, Servlet!
</h1></body></html>");
}
}
In this example, Shape is an abstract class with two abstract methods, area() and perimeter(). The Circle and Square classes are concrete subclasses of Shape, and they provide specific implementations for these abstract methods.
