Java Interview Questions and Answers
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What are the types of
statements in JDBC?-
Statement: to be used createStatement() method for executing single SQL
statement PreparedStatement — To be used preparedStatement() method for
executing same SQL statement over and over. CallableStatement — To be used
prepareCall() method for multiple SQL statements over and over.
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What is stored
procedure?-
Stored procedure is a group of SQL statements that forms a logical unit and
performs a particular task. Stored Procedures are used to encapsulate a set of
operations or queries to execute on database. Stored procedures can be compiled
and executed with different parameters and results and may have any combination
of input/output parameters.
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How to create and call
stored procedures?-
To create stored procedures: Create procedure procedurename (specify in, out
and in out parameters) BEGIN Any multiple SQL statement; END; To call stored
procedures: CallableStatement csmt = con. prepareCall(”{call procedure
name(?,?)}”); csmt. registerOutParameter(column no. , data type); csmt.
setInt(column no. , column name) csmt. execute();
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What is servlet?-
Servlets are modules that extend request/response-oriented servers, such as
java-enabled web servers. For example, a servlet might be responsible for
taking data in an HTML order-entry form and applying the business logic used to
update a company’s order database.
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What are the classes and
interfaces for servlets?-
There are two packages in servlets and they are javax. servlet and
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What is the difference
between an applet and a servlet?-
a) Servlets are to servers what applets are to browsers. b) Applets must have
graphical user interfaces whereas servlets have no graphical user interfaces.
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What is the difference
between doPost and doGet methods?-
a) doGet() method is used to get information, while doPost() method is used for
posting information. b) doGet() requests can’t send large amount of information
and is limited to 240-255 characters. However, doPost()requests passes all of
its data, of unlimited length. c) A doGet() request is appended to the request
URL in a query string and this allows the exchange is visible to the client,
whereas a doPost() request passes directly over the socket connection as part
of its HTTP request body and the exchange are invisible to the client.
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What is the life cycle
of a servlet?-
Each Servlet has the same life cycle: a) A server loads and initializes the
servlet by init () method. b) The servlet handles zero or more client’s
requests through service() method. c) The server removes the servlet through
destroy() method.
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Who is loading the
init() method of servlet?-
Web server
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What are the different
servers available for developing and deploying Servlets?-
a) Java Web Server b) JRun g) Apache Server h) Netscape Information Server i)
Web Logic
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How many ways can we
track client and what are they?-
The servlet API provides two ways to track client state and they are: a) Using
Session tracking and b) Using Cookies.
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What is session tracking
and how do you track a user session in servlets?-
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: a) 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. b) 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. c) 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. d) 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. e)
HttpSession- places a limit on the number of sessions that can exist in memory.
This limit is set in the session. maxresidents property.
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What is Server-Side
Includes (SSI)?-
Server-Side Includes allows embedding servlets within HTML pages using a
special servlet tag. In many servlets that support servlets, a page can be
processed by the server to include output from servlets at certain points
inside the HTML page. This is accomplished using a special internal SSINCLUDE,
which processes the servlet tags. SSINCLUDE servlet will be invoked whenever a
file with an. shtml extension is requested. So HTML files that include
server-side includes must be stored with an . shtml extension.
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What are cookies and how
will you use them?-
Cookies are a mechanism that a servlet uses to have a client hold a small
amount of state-information associated with the user. a) Create a cookie with
the Cookie constructor: public Cookie(String name, String value) b) A servlet
can send a cookie to the client by passing a Cookie object to the addCookie()
method of HttpServletResponse: public void HttpServletResponse.
addCookie(Cookie cookie) c) A servlet retrieves cookies by calling the
getCookies() method of HttpServletRequest: public Cookie[ ] HttpServletRequest.
getCookie().
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Is it possible to
communicate from an applet to servlet and how many ways and how?-
Yes, there are three ways to communicate from an applet to servlet and they
are: a) HTTP Communication(Text-based and object-based) b) Socket Communication
c) RMI Communication
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