Madanswer Technologies Interview Questions Data|Agile|DevOPs|Python - Recent questions and answers in Servlet

Answered: What is difference between Get and Post method?

Sun, 22 Oct 2023 14:10:51 +0000

Get method allows you to send a limited amount of data in the header. Post allows you to send a large amount of data in the body.

Answered: What is the use of attribute in servlets?

Wed, 12 Apr 2023 20:58:54 +0000

Attribute is a map object that can be used to set, get or remove in request, session or application scope. It is mainly used to share information between one servlet to another.

Answered: What is the use of welcome-file-list?

Wed, 12 Apr 2023 20:58:29 +0000

It is used to specify the welcome file for the project.

Answered: Which event is fired at the time of setting, getting or removing attribute from application scope?

Wed, 12 Apr 2023 20:58:04 +0000

ServletContextAttributeEvent.event is fired at the time of setting, getting or removing attribute from application scope

Answered: Which event is fired at the time of session creation and destroy?

Wed, 12 Apr 2023 20:57:29 +0000

HttpSessionEvent.is fired at the time of session creation and destroy

Answered: Which event is fired at the time of project deployment and undeployment?

Wed, 12 Apr 2023 20:56:55 +0000

ServletContextEvent.event is fired at the time of project deployment and undeployment

Answered: What are the annotations used in Servlet 3?

Wed, 12 Apr 2023 20:56:24 +0000

There are mainly 3 annotations used for the servlet.

@WebServlet : for servlet class.

@WebListener : for listener class.

@WebFilter : for filter class.

Answered: How to create war file?

Wed, 12 Apr 2023 20:55:34 +0000

The war file can be created using jar tool found in jdk/bin directory. If you are using Eclipse or Netbeans IDE, you can export your project as a war file.

To create war file from console, you can write following code.

jar -cvf abc.war *

Now all the files of current directory will be converted into abc.war file.

Answered: What is war file?

Wed, 12 Apr 2023 20:55:11 +0000

A war (web archive) file specifies the web elements. A servlet or jsp project can be converted into a war file. Moving one servlet project from one place to another will be fast as it is combined into a single file.

Answered: What if we pass negative value in load-on-startup?

Wed, 12 Apr 2023 20:54:51 +0000

It will not affect the container, now servlet will be loaded at first request.

Answered: What is load-on-startup in servlet?

Wed, 12 Apr 2023 20:54:18 +0000

The load-on-startup element of servlet in web.xml is used to load the servlet at the time of deploying the project or server start. So it saves time for the response of first request.

Answered: How can we upload the file to the server using servlet?

Wed, 12 Apr 2023 20:53:56 +0000

One of the way is by MultipartRequest class provided by third party.

Answered: What is the disadvantage of cookies?

Wed, 12 Apr 2023 20:53:38 +0000

It will not work if cookie is disabled from the browser.

Answered: How can we perform any action at the time of deploying the project?

Wed, 12 Apr 2023 20:53:16 +0000

By the help of ServletContextListener interface.

Answered: What is filter?

Wed, 12 Apr 2023 20:52:50 +0000

A filter is an object that is invoked either at the preprocessing or postprocessing of a request. It is pluggable.

Answered: What is difference between Cookies and HttpSession?

Wed, 12 Apr 2023 20:52:22 +0000

Cookie works at client side whereas HttpSession works at server side.

Answered: What are Cookies in servlet?

Tue, 11 Apr 2023 19:47:25 +0000

A cookie is a small piece of information that is persisted between the multiple client requests. A cookie has a name, a single value, and optional attributes such as a comment, path and domain qualifiers, a maximum age, and a version number.

Answered: What is Session Tracking?

Tue, 11 Apr 2023 19:46:47 +0000

Session simply means a particular interval of time.

Session Tracking is a way to maintain state of an user.Http protocol is a stateless protocol.Each time user requests to the server, server treats the request as the new request.So we need to maintain the state of an user to recognize to particular user.

Answered: Difference between forward() method and sendRedirect() method ?

Tue, 11 Apr 2023 19:46:21 +0000

The difference between SendRedirect and forward is one of the classical interview questions asked during a java web developer interview. This is not just applicable for servlet but also for JSP in which we can use forward action or call sendRedirect() method from scriptlet. Before examining the difference between forward and SendRedirect let’s see what send Redirect method and the forward method does.

SendRedirect ():

This method is declared in HttpServletResponse Interface.

Signature: void sendRedirect(String url)

This method is used to redirect the client requests to some other location for further processing, the new location is available on different servers or different contexts.

Our web container handles this and transfers the request using a browser, and this request is visible in the browser as a new request. Sometimes this is also called a client-side redirect.

Forward():

This method is declared in RequestDispatcher Interface.

Signature: forward(ServletRequest request, ServletResponse response)

This method is used to pass the request to another resource for further processing within the same server, another resource could be any servlet, jsp page any kind of file.

This process is taken care of by a web container when we call forward method request is sent to another resource without the client being informed, which resource will handle the request it has been mention on requestDispatcher object which we can get in two ways either using ServletContext or Request. This is also called a server-side redirect.

RequestDispatcher rd = request.getRequestDispatcher("pathToResource");
rd.forward(request, response);

RequestDispatcher rd = servletContext.getRequestDispatcher("/pathToResource");
rd.forward(request, response);

Difference between SendRedirect and Forward

Now let’s see some differences between these two methods of servlet API in tabular format.

Forward()	SendRediret()
When we use the forward method request is transferred to other resources within the same server for further processing.	In case of sendRedirect request is transferred to another resource to a different domain or different server for further processing.
In case of forward Web container handle all process internally and client or browser is not involved.	When you use the SendRedirect container transfers the request to the client or browser so url given inside the sendRedirect method is visible as a new request to the client.
When forward is called on requestdispather object we pass request and response object so our old request object is present on new resource which is going to process our request	In case of SendRedirect call old request and response object is lost because it’s treated as new request by the browser.
Visually we are not able to see the forwarded address, its is transparent	In the address bar we are able to see the new redirected address it’s not transparent.
Using the forward () method is faster than send a redirect.	SendRedirect is slower because one extra round trip is required because a completely new request is created and the old request object is lost. Two browser requests required.
When we redirect using forward and we want to use the same data in a new resource we can use the request.setAttribute () as we have request object available.	But in sendRedirect if we want to use we have to store the data in session or pass along with the URL.

Example of forwarding and SendRedirect in JSP Servlet:

Any kind of online payment when we use the merchant site will redirect us to the net banking site which is a completely new request it processes our request and again redirect to the merchant site?

In Banking Application when we do login normally we use the forward method. In the case of online banking, we are asked for a username and password if it’s correct some other servlet or resource will handle the request otherwise request has been forwarded to an error page.

Which one is good?

It depends upon the scenario that which method is more useful.

If you want control is transfer to a new server or context and it is treated as a completely new task then we go for Send Redirect.

Normally forward should be used if the operation can be safely repeated upon a browser reload of the web page will not affect the result.

SendRedirect and forward methods are still very useful while programming or working on any web application project using servlet jsp. This is still a popular interview question so don’t forget to revise forward and sendRedirect before appearing for any job interview.

Answered: Can you call a jsp from the servlet?

Tue, 11 Apr 2023 19:45:15 +0000

Yes, one of the way is RequestDispatcher interface for example:

RequestDispatcher rd=request.getRequestDispatcher("/login.jsp");

rd.forward(request,response);

Answered: What is the purpose of RequestDispatcher Interface?

Tue, 11 Apr 2023 19:44:49 +0000

The RequestDispacher interface provides the facility of dispatching the request to another resource it may be html, servlet or jsp. This interceptor can also be used to include the content of antoher resource.

Answered: What is servlet collaboration?

Tue, 11 Apr 2023 19:44:21 +0000

When one servlet communicates to another servlet, it is known as servlet collaboration. There are many ways of servlet collaboration:

RequestDispacher interface

sendRedirect() method etc.

Answered: What is difference between GenericServlet and HttpServlet?

Tue, 11 Apr 2023 19:43:58 +0000

The GenericServlet is protocol independent whereas HttpServlet is HTTP protocol specific. HttpServlet provides additional functionalities such as state management etc.

Answered: What is difference between PrintWriter and ServletOutputStream?

Tue, 11 Apr 2023 19:43:36 +0000

PrintWriter is a character-stream class where as ServletOutputStream is a byte-stream class. The PrintWriter class can be used to write only character-based information whereas ServletOutputStream class can be used to write primitive values as well as character-based information.

Answered: When servlet object is created?

Tue, 11 Apr 2023 19:42:24 +0000

At the time of first request.

Answered: Who is responsible to create the object of servlet?

Tue, 11 Apr 2023 19:41:57 +0000

The web container or servlet container.

Answered: What are the life-cycle methods for a servlet?

Tue, 11 Apr 2023 19:41:35 +0000

Below are the life-cycle methods for a servlet

Method	Description
public void init(ServletConfig config)	It is invoked only once when first request comes for the servlet. It is used to initialize the servlet.
public void service(ServletRequest request,ServletResponse)throws ServletException,IOException	It is invoked at each request.The service() method is used to service the request.
public void destroy()	It is invoked only once when servlet is unloaded.

Answered: What is the life-cycle of a servlet?

Tue, 11 Apr 2023 19:40:47 +0000

life-cycle of a servlet :

Servlet is loaded
servlet is instantiated
servlet is initialized
service the request
servlet is destroyed

Answered: How many objects of a servlet is created?

Tue, 11 Apr 2023 19:40:04 +0000

Only one object at the time of first request by servlet or web container.