Servlet

URI And URL Difference

Before going into URL and URI, you need to know some background. Do you ever thought about, who decides what is URL? and what is URI? or who is the authority for URL, URI and such naming conventions? W3C and IETF There are two separate bodies W3C and IETF. The World Wide Web Consortium (W3C) [...]

Session Life Cycle

When I say life cycle, I can hear you murmur “Oh no not again, how many life cycles I have to deal with”! In real world everything has life cycle, then why not in programming, after all, software is all about mimicking real life.  In a previous article I discussed about methods used for session [...]

Servlet JSP Communication

getServletConfig().getServletContext().getRequestDispatcher(“jspfilepathtoforward”).forward(request, response); The above line is essence of the answer for “How does a servlet communicate with a JSP page?” When a servlet jsp communication is happening, it is not just about forwarding the request to a JSP from a servlet. There might be a need to transfer a string value or on object itself. [...]

Session Tracking Methods

Following answer is applicable irrespective of the language and platform used. Before we enter into session tracking, following things should be understood. What is a session? A session is a conversation between the server and a client. A conversation consists series of continuous request and response. Why should a session be maintained? When there is [...]

What happens if you call destroy() from init() in java servlet?

destroy() gets executed and the initialization process continues. It is a trick question in servlets interview. 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 [...]

How to avoid IllegalStateException in java servlet?

The root cause of IllegalStateException exception is a java servlet is attempting to write to the output stream (response) after the response has been committed. It is always better to ensure that no content is added to the response after the forward or redirect is done to avoid IllegalStateException. It can be done by including [...]

What is servlet mapping?

Servlet mapping specifies the web container of which java servlet should be invoked for a url given by client. It maps url patterns to servlets. When there is a request from a client, servlet container decides to which application it should forward to. Then context path of url is matched for mapping servlets. How is [...]

Difference between HttpServlet and GenericServlet

javax.servlet.GenericServlet Signature: public abstract class GenericServlet extends java.lang.Object implements Servlet, ServletConfig, java.io.Serializable GenericServlet defines a generic, protocol-independent servlet. GenericServlet gives a blueprint and makes writing servlet easier. GenericServlet provides simple versions of the lifecycle methods init and destroy and of the methods in the ServletConfig interface. GenericServlet implements the log method, declared in the ServletContext [...]

What is preinitialization of a java servlet?

In the java servlet life cycle, the first phase is called ‘Creation and intialization’. The java servlet container first creates the servlet instance and then executes the init() method. This initialization can be done in three ways. The default way is that, the java servlet is initialized when the servlet is called for the first [...]

Difference between ServletConfig and ServletContext

Signature: public interface ServletConfig ServletConfig is implemented by the servlet container to initialize a single servlet using init(). That is, you can pass initialization parameters to the servlet using the web.xml deployment descriptor. For understanding, this is similar to a constructor in a java class. Example code: <servlet> <servlet-name>ServletConfigTest</servlet-name> <servlet-class>com.javapapers.ServletConfigTest</servlet-class> <init-param> <param-name>topic</param-name> <param-value>Difference between ServletConfig [...]