To get started with Servlets, let’s first start with a simple Servlet application i.e LifeCycle application, that will demonstrate the implementation of the init(), service() and destroy() methods. First of all it is important to understand that if we are developing any Servlet application, it will handle some client’s request so, whenever we talk about Servlets we need to develop a index.
Servlet constructor and init() method (6). Servlet is an interface. An interface can't define constructors. This is the reason why it has been defined an init method to call after the instantiation of the servlet. There was no other possibility to initialize the Servlet passing a ServletConfig.
Servlet instance is created. init method is invoked. service method is invoked. destroy method is invoked. As displayed in the above diagram, there are three states of a servlet: new, ready and end. The servlet is in new state if servlet instance is created. After invoking the init() method, Servlet comes in the ready state.Initializing a Servlet After the web container loads and instantiates the servlet class and before it delivers requests from clients, the web container initializes the servlet. To customize this process to allow the servlet to read persistent configuration data, initialize resources, and perform any other one-time activities, you override the init method of the Servlet interface.It provides simple versions of the lifecycle methods init and destroy and of the methods in the ServletConfig interface. GenericServlet also implements the log method, declared in the ServletContext interface. To write a generic servlet, you need only override the abstract service method. Author: Various See Also: Serialized Form.
Servlet instance instantiation is different and calling init() is different. usually we will keep the logic like acquiring any DB connections, any other resources etc are handled in init() method. With the completion of init(), the servlet is ready to handle any request.Read More
In java servlet, destroy() is not supposed to be called by the programmer. But, if it is invoked, it gets executed. The implicit question is, will the servlet get destroyed? No, it will not. destroy() method is not supposed to and will not destroy a java servlet. Don’t get confused by the name. It should have been better, if it was named.Read More
How Servlet works? It is important to learn how servlet works for understanding the servlet well. Here, we are going to get the internal detail about the first servlet program. The server checks if the servlet is requested for the first time. If yes, web container does the following tasks: loads the servlet class. instantiates the servlet class.Read More
LIFE CYCLE METHODS of servlets: In servlets we have three life cycle methods, they are. public void init (); public void service (ServletRequest req, ServletResponse res); public void destroy (); public void init (): Whenever client makes a request to a servlet, the server will receive the request and it automatically calls init method i.e., init method will be called only one time by the.Read More
The init method is designed to be called only once. If an instance of the servlet does not exist, the web container: Loads the servlet class; Creates an instance of the servlet class; Initializes it by calling the init method; The init method must complete successfully before the servlet can receive any requests. The servlet container cannot place the servlet into service if the init method.Read More
Servlet specification provides a way to provide init parameters to the servlet when it is initialized. i.e. its init method completes. These init parameters are available in the servlet. Parameters can be accessed using public String getInitParameter (String name) method. Step 1: Create a dynamic web project.Read More
In the init method of my servlet I am trying to write out to the console (dos console). I have understood that the servlet container call the init method when the servlet is first instantiated and passes it a ServletConfig object.Read More
Output screenshot on Servlet Constructor. By the above screen, you can conclude constructor is called. Reasons for not preferring to write a Servlet Constructor. init() is one of the life cycle methods called implicitly after container creates a Servlet object. The overloaded init() method takes an object of ServletConfig as parameter.Read More
It is container which is responsible to manage the life-cycle of servlet. Web server hands the request to web container in which servlet is deployed and not to Servlet itself. Then container provides request and response to servlet. It is container which calls the servlet’s method. Tomcat is the example of Servlet container. How it works.Read More
Wish below 2 article can give you some help. They introduce all about java servlet. Thanks. init() This is called when the container load and create the servlet instance. You can do any initialization actions such as read initialization parameters.Read More