Difference between Constructor vs Init method in Servlet? Interview Question Answer

In the context of Servlets, the terms "constructor" and "init method" refer to different concepts. Let's discuss each one separately:

Constructor: In Java, a constructor is a special method that is used to initialize an object of a class. It is called when an object is created using the new keyword. Constructors are used to set initial values for instance variables or perform any necessary setup for the object. In the context of Servlets, the constructor is typically used to initialize the Servlet instance itself.

Init method: The init method in a Servlet is part of the Servlet lifecycle. It is invoked by the Servlet container (such as Tomcat or Jetty) after the Servlet is instantiated, but before it starts handling requests. The init method is responsible for any initialization tasks required by the Servlet, such as opening a database connection, loading configuration data, or setting up resources.

To summarize:

The constructor is a general concept in Java used to initialize objects of a class.

The init method is a specific method defined by the Servlet specification that is called by the Servlet container to initialize a Servlet before it starts processing requests.

In a Servlet, both the constructor and the init method can be used to perform initialization tasks. However, it's important to note that the init method is the recommended place to perform Servlet-specific initialization, as it follows the Servlet lifecycle defined by the Servlet specification.