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Java EE - Interview Questions and Answers for 'Java EE' - 58 question(s) found - Order By Newest

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 Q1. What is session tracking and how do you track a user session in servlets?Java EE
Ans. Session tracking is a mechanism that servlets use to maintain state about a series requests from the same user across some period of time. The methods used for session tracking are:

User Authentication - occurs when a web server restricts access to some of its resources to only those clients that log in using a recognized username and password

Hidden form fields - fields are added to an HTML form that are not displayed in the client's browser. When the form containing the fields is submitted, the fields are sent back to the server

URL rewriting - every URL that the user clicks on is dynamically modified or rewritten to include extra information. The extra information can be in the form of extra path information, added parameters or some custom, server-specific URL change.

Cookies - a bit of information that is sent by a web server to a browser and which can later be read back from that browser.

HttpSession- places a limit on the number of sessions that can exist in memory.

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   Like         Discuss         Correct / Improve     j2ee   servlets   session   session management   web applications   cookies   httpsession   url rewriting   architecture     Asked in 1 Companies


 Q2. what is the use of cookie and session ? and What is the difference between them ?Java EE
Ans. Cookie and Session are used to store the user information. Cookie stores user information on client side and Session does it on server side. Primarily, Cookies and Session are used for authentication, user preferences, and carrying information across multiple requests. Session is meant for the same purpose as the cookie does. Session does it on server side and Cookie does it on client side. One more thing that quite differentiates between Cookie and Session. Cookie is used only for storing the textual information. Session can be used to store both textual information and objects.

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   Like         Discuss         Correct / Improve     session   session management   java   cookies   authentication   web application   ebay      intermediate


Frequently asked. Among first few questions in the J2EE segment of interview.
  Q3. What is deployment descriptor ?

or

What is the use of deployment descriptor ?
Java EE
Ans. Deployment Descriptor which is usually web.xml is used to specify the classes, resources and configuration of the application and how the web server uses them to serve web requests.This file is usually added to WEB-INF folder and contains following

* Servlet entries and url mapping
* Plugins
* Some info regarding authentication / filters
* Landing Page
* Event Handlers

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   Like         Discuss         Correct / Improve     web.xml   servlets  deployment descriptor     Asked in 15 Companies      basic        frequent

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 Q4. Difference between the jsp scriptlet tag and jsp declaration tag?Java EE
Ans. The jsp scriptlet tag can only declare variables not methods whereas jsp declaration tag can declare variables as well as methods.

The declaration of scriptlet tag is placed inside the _jspService() method whereas The declaration of jsp declaration tag is placed outside the _jspService() method.

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   Like         Discuss         Correct / Improve     j2ee   jsp   scriptlet tag   declaraation tag   web application


 Q5. Which of the following file is called deployment descriptor ?

a. application.xml
b. project.xml
c. web.xml
d. build.xml
Java EE
Ans. web.xml

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   Like         Discuss         Correct / Improve     configuration files   deployment   server   java


 Q6. What is URL?
Java EE
Ans. URL is Uniform Resource Locator which is representation of HTTP address.

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   Like         Discuss         Correct / Improve     j2ee   http   internet   url      basic        rare


 Q7. What is HTTP ?Java EE
Ans. HTTP or Hypertext Transfer Protocol is internet protocol for tranmission of hypertext ( text with meta data ) over internet.

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   Like         Discuss         Correct / Improve     j2ee   http   internet  fidelity     Asked in 2 Companies      basic        frequent


 Q8. Can we have multiple servlets in a web application and How can we do that ?Java EE
Ans. Yes by making entries in web.xml

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   Like         Discuss         Correct / Improve     j2ee   servlets   servelets   web application   java   web.xml   yes-no   architecture


 Q9. Difference between socket and servlet ?Java EE
Ans. servlet is a small, server-resident program that typically runs automatically in response to user input.
A network socket is an endpoint of an inter-process communication flow across a computer network.

We can think of it as a difference between door and gate. They are similar as they both are entry points but they are different as they are put up at different areas.

Sockets are for low-level network communication whereas Servlets are for implementing websites and web services

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   Like         Discuss         Correct / Improve     java   j2ee   networking   servlet   socket   difference between.java.net   technologies   architecture


 Q10. What are different types of cookies ?Java EE
Ans. Session cookies , which are deleted once the session is over.

Permanent cookies , which stays at client PC even if the session is disconnected.

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   Like         Discuss         Correct / Improve     j2ee   servlets   session   session management   web applications   cookies   httpsession


 Q11. What is a Servlet Filter ?Java EE
Ans. It's an object that can intercept http request and response and hence we can take appropriate action on those requests.

There are different types of filters based on Specifications like

Authentication
Logging
Encryption
Tokenizing

etc

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   Like         Discuss         Correct / Improve     servlets  servlet filters     Asked in 3 Companies      basic        frequent


 Q12. What are some uses of interceptors ?Java EE
Ans. Authentication / Authorization
URL forwarding
Auditing / Logging
Localization

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   Like         Discuss         Correct / Improve     interceptors  interceptor design pattern


  Q13. What is a cookie ?Java EE
Ans. A cookie is a small piece of text stored on a user's computer by the browser for a specific domain. Commonly used for authentication, storing site preferences, and server session identification.

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   Like         Discuss         Correct / Improve     cookie   javascript   web application   session management   browser   j2ee     Asked in 16 Companies      basic        frequent


 Q14. What is servlet Chaining ?Java EE
Ans. Multiple servlets serving the request in chain.

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 Q15. What is a config Object?
Java EE
Ans. The config object is an instantiation of javax.servlet.ServletConfig and is a direct wrapper around the ServletConfig object for the generated servlet. This object allows the JSP programmer access to the Servlet or JSP engine initialization parameters such as the paths or file location.

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   Like         Discuss         Correct / Improve     j2ee   servlet   jsp   servlet config   servletconfig   javax


 Q16. What is a pageContext Object?
Java EE
Ans. The pageContext object is an instance of a javax.servlet.jsp.PageContext object. The pageContext object is used to represent the entire JSP page. This object stores references to the request and response objects for each request. The application, config, session, and out objects are derived by accessing attributes of this object.The pageContext object also contains information about the directives issued to the JSP page, including the buffering information, the errorPageURL, and page scope.

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   Like         Discuss         Correct / Improve     j2ee   servlet   jsp   pagecontext   page context


 Q17. What are LDAP servers used for ?Java EE
Ans. LDAP servers are typically used in J2EE applications to authenticate and authorise users. LDAP servers are hierarchical and are optimized for read access, so likely to be faster than database in providing read access.

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   Like         Discuss         Correct / Improve     java   j2ee   ldap   servers   authentication   authorization   architecture   technical lead   technical architect  production support     Asked in 1 Companies


 Q18. What are the phases of the JSP life cycle ?Java EE
Ans. Translation of JSP PageCompilation of JSP PageClassloading (class file is loaded by the classloader)Instantiation (Object of the Generated Servlet is created).Initialization ( jspInit() method is invoked by the container).Reqeust processing ( _jspService() method is invoked by the container).Destroy ( jspDestroy() method is invoked by the container).

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 Q19. What are JSP directives ? What are different types of directives ?Java EE
Ans. The jsp directives are messages that tells the web container how to translate a JSP page into the corresponding servlet.

There are three types of directives -

page directive
include directive
taglib directive

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   Like         Discuss         Correct / Improve     j2ee   servlets   servelets   web application   jsp   jsp ldirectives


 Q20. What are advantages of using Servlets over CGI ?Java EE
Ans. Better Performance as Servlets doesn't require a separate process for a single request.

Servlets are platform independent as they are written in Java.

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 Q21. What is the use of HTTPSession in relation to http protocol ?Java EE
Ans. http protocol on its own is stateless. So it helps in identifying the relationship between multiple stateless request as they come from a single source.

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 Q22. Why using cookie to store session info is a better idea than just using session info in the request ?Java EE
Ans. Session info in the request can be intercepted and hence a vulnerability. Cookie can be read and write by respective domain only and make sure that right session information is being passed by the client.

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 Q23. http protocol is by default ... ?Java EE
Ans. stateless

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 Q24. How many SessionFactory and Session objects are created ?Java EE
Ans. Single SessionFactory object and multiple session objects for opening different session. Hibernate creates new Session object per thread.

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  Q25. Difference between jar , war and ear ?Java EE
Ans. Jar is Java Archieve i.e compressed Class or Class / Java files.

War comprises of compressed Servlet class files,JSP FIles,supporting files, GIF and HTML files.

Ear comprise of compressed Java and web module files ( was files ).

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 Q26. What doesn Http keep alive header does ?Java EE
Ans. Http is connection less by default. header informs hosts to keep the connection alive so that the same connection can be reused for multiple communication.

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 Q27. Are Servlet classes Thread Safe ?Java EE
Ans. No

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 Q28. What do you know about JQuery ?Java EE
Ans. jQuery is a cross platform JavaScript library designed to simplify the client-side scripting of HTML. JQuery is the most popular JavaScript library.

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 Q29. What is an IP address ?Java EE
Ans. An Internet Protocol address is a numerical label assigned to each device participating in a computer network.

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   Like         Discuss         Correct / Improve     ip address     Asked in 2 Companies      basic        frequent


 Q30. What is the difference between URI, URL and URN ?Java EE
Ans. URI stands for Uniform Resource Indicator
URL stands for Uniform Resource Locator
URN stands for Uniform Resource Name

URI = URL + URN

For ex - http://javasearch.buggybread.com/InterviewQuestions/questionSearch.php?keyword=url

This is URI. The string from start till .php is URL whereas keyword=url is URN.

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