Top 25+ JSP Interview Questions & Answers [ JAVA TRICKS ] |ACTE
JSP Interview Questions and Answers

Top 25+ JSP Interview Questions & Answers [ JAVA TRICKS ]

Last updated on 04th Jul 2020, Blog, Interview Questions

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These JSP Interview Questions have been designed specially to get you acquainted with the nature of questions you may encounter during your interview for the subject of JSP As per my experience good interviewers hardly plan to ask any particular question during your interview, normally questions start with some basic concept of the subject and later they continue based on further discussion and what you answer .we are going to cover top 100 JSP Interview questions along with their detailed answers. We will be covering JSP scenario based interview questions JSP interview questions for fresher’s as well as interview JSP questions and answers for experienced

1) What are the JSP lifecycle phases?

Ans:

If you will look into JSP page code, it looks like HTML and doesn’t look anything like java classes. Actually JSP container takes care of translating the JSP pages and create the servlet class that is used in web application. JSP lifecycle phases are:

  • Translation – JSP containers checks the JSP page code and parses it to generate the servlet source code. For example in Tomcat you will find generated servlet class files at TOMCAT/work/Catalina/localhost/WEBAPP/org/apache/jsp directory. If the JSP page name is home.jsp, usually the generated servlet class name is home_jsp and file name is home_jsp.java
  • Compilation – JSP container compiles the jsp class source code and produce class file in this phase.
  • Class Loading – Container loads the class into memory in this phase.
  • Instantiation – Container invokes the no-args constructor of generated class to load it into memory and instantiate it.
  • Initialization – Container invokes the init method of JSP class object and initializes the servlet config with init params configured in deployment descriptor. After this phase, JSP is ready to handle client requests. Usually from translation to initialization of JSP happens when first request for JSP comes but we can configure it to be loaded and initialized at the time of deployment like servlets using load-on-startup element.
  • Request Processing – This is the longest lifecycle of JSP page and JSP page processes the client requests. The processing is multi-threaded and similar to servlets and for every request a new thread is spawned and ServletRequest and ServletResponse object is created and JSP service method is invoked.
  • Destroy – This is the last phase of JSP lifecycle where JSP class is unloaded from memory. Usually it happens when application is undeployed or the server is shut down.

2) What are JSP lifecycle methods?

Ans:

JSP lifecycle methods are:

  • jspInit(): This method is declared in JspPage and it’s implemented by JSP container implementations. This method is called once in the JSP lifecycle to initialize it with config params configured in deployment descriptor. We can override this method using JSP declaration scripting element to initialize any resources that we want to use in JSP page.
  • _jspService(): This is the JSP method that gets invoked by JSP container for each client request by passing request and response object. Notice that method name starts with underscore to distinguish it from other lifecycle methods because we can’t override this method. All the JSP code goes inside this method and it’s overridden by default. We should not try to override it using JSP declaration scripting element. This method is defined in HttpJspPage interface.
  • jspDestroy(): This method is called by container when JSP is unloaded from memory such as shutting down application or container. This method is called only once in JSP lifecycle and we should override this method to release any resources created in JSP init method.

3)Which JSP lifecycle methods can be overridden?

Ans:

We can override jspInit() and jspDestroy() methods using JSP declaration scripting element. We should override jspInit() methods to create common resources that we would like to use in JSP service method and override jspDestroy() method to release the common resources.

4) How can we avoid direct access of JSP pages from client browser?

Ans:

We know that anything inside the WEB-INF directory can’t be accessed directly in a web application, so we can place our JSP pages in WEB-INF directory to avoid direct access to JSP page from the client browser. But in this case, we will have to configure it in deployment descriptor just like Servlets. The sample configuration is given below code snippet of web.xml file.

  • <servlet>
  • <servlet-name>Test</servlet-name>
  • <jsp-file>/WEB-INF/test.jsp</jsp-file>
  • <init-param>
  • <param-name>test</param-name>
  • <param-value>Test Value</param-value>
  • </init-param>
  • </servlet>
  • <servlet-mapping>
  • <servlet-name>Test</servlet-name>
  • <url-pattern>/Test.do</url-pattern>
  • </servlet-mapping>

5) What are different types of comments in JSP?

Ans:

JSP pages provide two types of comments that we can use:

  • HTML Comments: Since JSP pages are like HTML, we can use HTML comments like <!– HTML Comment –>. These comments are sent to client also and we can see it in HTML source. So we should avoid any code level comments or debugging comments using HTML comments.
  • JSP Comments: JSP Comments are written using scriptlets like <%– JSP Comment –%>. These comments are present in the generated servlet source code and doesn’t sent to client. For any code level or debugging information comments we should use JSP comments.

6) What is Scriptlet, Expression and Declaration in JSP?

Ans:

  • Scriptlets, Expression and Declaration are scripting elements in JSP page using which we can add java code in the JSP pages.
  • A scriptlet tag starts with <% and ends with %>. Any code written inside the scriptlet tags go into the _jspService() method. For example;
  • <%
  • Date d = new Date();
  • System.out.println(“Current Date=”+d);
  • %>
  • Since most of the times we print dynamic data in JSP page using out.print() method, there is a shortcut to do this through JSP Expressions. JSP Expression starts with <%= and ends with %>.
  • <% out.print(“Pankaj”); %> can be written using JSP Expression as <%= “Pankaj” %>
  • Notice that anything between <%= %> is sent as parameter to out.print() method. Also notice that scriptlets can contain multiple java statements and always ends with semicolon (;) but expression doesn’t end with semicolon.
  • JSP Declarations are used to declare member methods and variables of servlet class. JSP Declarations starts with <%! and ends with %>.
  • For example: we can create an int variable in JSP at class level as <%! public static int count=0; %>.

7)What are JSP implicit objects?

Ans:

JSP implicit objects are created by container while translating JSP page to Servlet source to help developers. We can use these objects directly in scriptlets that goes in service method, however we can’t use them in JSP Declaration because that code will go at class level.

We have 9 implicit objects that we can directly use in JSP page. Seven of them are declared as local variable at the start of _jspService() method whereas two of them are part of _jspService() method argument that we can use.

  • out Object
  • request Object
  • response Object
  • config Object
  • application Object
  • session Object
  • pageContext Object
  • page Object
  • exception Object

JSP Implicit Objects Example:

Read in detail about each one of them at JSP Implicit Objects.

8) Can we use JSP implicit objects in a method defined in JSP Declaration?

Ans:

No we can’t because JSP implicit objects are local to service method and added by JSP Container while translating JSP page to servlet source code. JSP Declarations code goes outside the service method and used to create class level variables and methods and hence can’t use JSP implicit objects.

9) Which implicit object is not available in normal JSP pages?

Ans:

JSP exception implicit object is not available in normal JSP pages and it’s used in JSP error pages only to catch the exception thrown by the JSP pages and provide useful message to the client.

10) What are the benefits of PageContext implicit object?

Ans:

  • JSP pageContext implicit object is instance of javax.servlet.jsp.PageContext abstract class implementation. We can use pageContext to get and set attributes with different scopes and to forward request to other resources. pageContext object also hold reference to other implicit object.
  • This is the only object that is common in both JSP implicit objects and in JSP EL implicit objects.

11) How do we configure init params for JSP?

Ans:

We can configure init params for JSP similar to servlet in web.xml file, we need to configure JSP init params with servlet and servlet-mapping element. The only thing differs from servlet is jsp-file element where we need to provide the JSP page location.

12) Why use of scripting elements in JSP is discouraged?

Ans:

  • JSP pages are mostly used for view purposes and all the business logic should be in the servlet or model classes. We should pass parameters to JSP page through attributes and then use them to create the HTML response in JSP page.
  • Most part of the JSP page contains HTML code and to help web designers to easily understand JSP page and develop them, JSP technology provides action elements, JSP EL, JSP Standard Tag Library and custom tags that we should use rather than scripting elements to bridge the gap between JSP HTML part and JSP java part.

13) Can we define a class in a JSP Page?

Ans:

It’s not a good practice though, but we can define a class inside a JSP Page. Below is the sample code for this:

  • <%!
  • private static class NestedClass { //static is better because Servlet is multi-threaded
  • private final int num = 0;
  • public int getNum() {return num;}}
  • %>
  • Or
  • <%
  • class Person { //this will go inside method body, so can’t be public}
  • %>

14) How can we disable java code or scripting in JSP page?

Ans:

We can disable scripting elements in JSP pages through deployment descriptor configuration like below.

  • <jsp-config>
  • <jsp-property-group>
  • <url-pattern>*.jsp</url-pattern>
  • <scripting-invalid>true</scripting-invalid>
  • </jsp-property-group>
  • </jsp-config>

Above URL-pattern will disable scripting for all the JSP pages but if you want to disable it only for a specific page, you can give the JSP file name itself.

15)Explain JSP Action Elements or Action Tags?

Ans:

JSP action elements or action tags are HTML like tags that provide useful functionalities such as working with Java Bean, including a resource, forwarding the request and to generate dynamic XML elements. JSP action elements always starts with jsp: and we can use them in JSP page directly without the need to import any tag libraries or any other configuration changes. Some of the important action elements are jsp:useBean, jsp:getProperty, jsp:setProperty, jsp:include and jsp:forward.

16) What is difference between include directive and jsp:include action?

Ans:

  • The difference between JSP include directive and include action is that in include directive the content to other resource is added to the generated servlet code at the time of translation whereas with include action it happens at runtime.
  • Another difference is that in JSP include action, we can pass params to be used in the included resource with jsp:param action element but in JSP include directive we can’t pass any params.
  • When the included resource is static such as header, footer, image files then we should use include directive for faster performance but if the included resource is dynamic and requires some parameters for processing then we should use include action tag.

17) What is JSP Expression Language and what are it’s benefits?

Ans:

  • Most of the times we use JSP for view purposes and all the business logic is present in servlet code or model classes. When we receive client request in the servlet, we process it and then add attributes in request/session/context scope to be retrieved in JSP code. We also use request params, headers, cookies and init params in JSP to create response views.
  • We can use scriptlets and JSP expressions to retrieve attributes and parameters in JSP with java code and use it for view purpose. But for web designers, java code is hard to understand and that’s why JSP Specs 2.0 introduced Expression Language (EL) through which we can get attributes and parameters easily using HTML like tags.
  • Expression language syntax is ${name} and we can use EL implicit objects and EL operators to retrieve the attributes from different scopes and use them in JSP pag.

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    18) What are JSP EL implicit objects and how it’s different from JSP implicit Objects?

    Ans:

    JSP Expression Language provides many implicit objects that we can use to get attributes from different scopes and parameter values. Note that these are different from JSP implicit objects and contains only the attributes in given scope. The only common implicit object in JSP EL and JSP page is pageContext object.

    • Below table provides a list of implicit object in JSP EL.
    • JSP EL Implicit Objects Type Description
    • PageScope Map A map that contains the attributes set with page scope.
    • RequestScope Map Used to get the attribute value with request scope.
    • SessionScope Map Used to get the attribute value with session scope.
    • ApplicationScope Map Used to get the attributes value from application scope.
    • Param Map Used to get the request parameter value, returns a single value
    • ParamValues Map Used to get the request param values in an array, useful when request parameter contain multiple values.
    • Header Map Used to get request header information.
    • HeaderValues Map Used to get header values in an array.
    • Cookie Map Used to get the cookie value in the JSP
    • InitParam Map Used to get the context init params, we can’t use it for servlet init params
    • PageContext pageContext Same as JSP implicit pageContext object, used to get the request, session references etc. example usage is getting request HTTP Method name.

    19) How to use JSP EL to get HTTP method name?

    Ans:

    We can use pageContext JSP EL implicit object to get the request object reference and use dot operator to get the HTTP method name in JSP page. The JSP EL code for this will be ${pageContext.request.method}.

    20) What is JSP Standard Tag Library, provide some example usage?

    Ans:

    • JSP Standard Tag Library or JSTL is more versatile than JSP EL or Action elements because we can loop through a collection or escape HTML tags to show them like text in response.
    • JSTL is part of the Java EE API and included in most servlet containers. But to use JSTL in our JSP pages, we need to download the JSTL jars for your servlet container. Most of the times, you can find them in the example projects and you can use them. You need to include these libraries in the project WEB-INF/lib directory. These jars are container specific, for example in Tomcat, we need to include jstl.jar and standard.jar jar files in the project build path.

    21) What are the types of JSTL tags?

    Ans:

    Based on the JSTL functions, they are categorized into five types.

    • Core Tags – Core tags provide support for iteration, conditional logic, catch exception, url, forward or redirect response etc.
    • Formatting and Localization Tags – These tags are provided for formatting of Numbers, Dates and i18n support through locales and resource bundles.
    • SQL Tags – JSTL SQL Tags provide support for interaction with relational databases such as Oracle, MySql etc.
    • XML Tags – XML tags are used to work with XML documents such as parsing XML, transforming XML data and XPath expressions evaluation.
    • JSTL Functions Tags – JSTL tags provide a number of functions that we can use to perform common operation, most of them are for String manipulation such as String Concatenation, Split String etc.

    22) What is JSP Custom Tag and what are it’s components?

    Ans:

    Sometimes JSP EL, Action Tags and JSTL tags are not enough and we might get tempted to write java code to perform some operations in JSP page. Fortunately JSP is extendable and we can create our own custom tags to perform certain operations.

    • We can create JSP Custom Tags with following components:
    • JSP Custom Tag Handler
    • Creating Tag Library Descriptor (TLD) File
    • Deployment Descriptor Configuration for TLD
    • We can add custom tag library in JSP page using taglib directive and then use it.

    23) Give an example where you need JSP Custom Tag?

    Ans:

    Let’s say we want to show a number with formatting with commas and spaces. This can be very useful for user when the number is really long. So we want some custom tags like below:

    • <mytags:formatNumber number=”123456.789″ format=”#,###.00″/>

    • Based on the number and format passed, it should write the formatted number in JSP page, for the above example it should print 123,456.79
    • We know that JSTL doesn’t provide any inbuilt tags to achieve this, so we will create our own custom tag implementation and use it in the JSP page.


    24) Why don’t we need to configure JSP standard tags in web.xml?

    Ans:

    We don’t need to configure JSP standard tags in web.xml because the TLD files are inside the META-INF directory of the JSTL jar files. When container loads the web application and finds TLD files inside the META-INF directory of the JAR file, it automatically configures them to be used directly in the application JSP pages. All we need to do it to include it in the JSP page using taglib directive.

    25) How can we handle exceptions thrown by JSP service method?

    Ans:

    • To handle exceptions thrown by the JSP page, all we need is an error page and define the error page in JSP using page directive.
    • To create a JSP error page, we need to set the page directive attribute isErrorPage value to true, then we can access exception implicit object in the JSP and use it to send a customized error message to the client.
    • We need to define exception and error handler JSP pages in the deployment descriptor like below.
    • <error-page>
    • <error-code>404</error-code>
    • <location>/error.jsp</location>
    • </error-page>
    • <error-page>
    • <exception-type>java.lang.Throwable</exception-type>
    • <location>/error.jsp</location>
    • </error-page>

    26) How do we catch exception and process it using JSTL?

    Ans:

    We can use JSTL Core tags c:catch and c:if to catch exception inside the JSP service method and process it. c:catch tag catches the exception and wraps it into the exception variable and we can use c:if condition tag to process it. Below code snippet provide sample usage.

    • <c:catch var =”exception”>
    • <% int x = 5/0;%>
    • </c:catch>
    • <c:if test = “${exception ne null}”>
    • <p>Exception is : ${exception} <br />
    • Exception Message: ${exception.message}</p>
    • </c:if>

    27) How do we print “<br> creates a new line in HTML” in JSP?

    Ans:

    We can use c:out escapeXml attribute to escape the HTML elements so that it get’s shown as text in the browser, for this scenario we will write code like below.

    • <c:out value=”<br> creates a new line in HTML” escapeXml=”true”></c:out>

    28) What is jsp-config in deployment descriptor?

    Ans:

    jsp-config element is used to configure different parameters for JSP pages. Some of it’s usage are:

    Configuring tag libraries for the web application like below.

    • <jsp-config>
    • <taglib>
    • <taglib-uri>https://journaldev.com/jsp/tlds/mytags</taglib-uri>
    • <taglib-location>/WEB-INF/numberformatter.tld</taglib-location>
    • </taglib>
    • </jsp-config>
    • We can control scripting elements in JSP pages.
    • We can control JSP Expression Language (EL) evaluation in JSP pages.
    • We can define the page encoding for URL pattern.
    • To define the buffer size to be used in JSP page out object.
    • To denote that the group of resources that match the URL pattern are JSP documents, and thus must be interpreted as XML documents.

    29) How to ignore the EL expression evaluation in a JSP?

    Ans:

    We can ignore EL evaluation in JSP page by two ways.

    Using page directive as <%@ page isELIgnored=”true” %>

    Configuring in web.xml – better approach when you want to disable EL evaluation for many JSP pages.

    • <jsp-config>
    • <jsp-property-group>
    • <url-pattern>*.jsp</url-pattern>
    • <el-ignored>true</el-ignored>
    • </jsp-property-group>
    • </jsp-config>

    30) When will Container initialize multiple JSP/Servlet Objects?

    Ans:

    If we have multiple servlet and servlet-mapping elements in deployment descriptor for a single servlet or JSP page, then container will initialize an object for each of the element and all of these instances will have their own ServletConfig object and init params.

    For example, if we configure a single JSP page in web.xml like below.

    • <servlet>
    • <servlet-name>Test</servlet-name>
    • <jsp-file>/WEB-INF/test.jsp</jsp-file>
    • <init-param>
    • <param-name>test</param-name>
    • <param-value>Test Value</param-value>
    • </init-param>
    • </servlet>
    • <servlet-mapping>
    • <servlet-name>Test</servlet-name>
    • <url-pattern>/Test.do</url-pattern>
    • </servlet-mapping>
    • <servlet>
    • <servlet-name>Test1</servlet-name>
    • <jsp-file>/WEB-INF/test.jsp</jsp-file>
    • </servlet>
    • <servlet-mapping>
    • <servlet-name>Test1</servlet-name>
    • <url-pattern>/Test1.do</url-pattern>
    • </servlet-mapping>

    Then if we can access the same JSP page with both the URI pattern and both will have their own init params values.

    31)Can we use JavaScript with JSP Pages?

    Ans:

    Yes why not, I have seen some developers getting confused with this. Even though JSP is a server-side technology, it’s used to generate a client-side response and we can add javascript or CSS code like any other HTML page.

    32) How can we prevent implicit session creation in JSP?

    Ans:

    By default JSP page creates a session but sometimes we don’t need session in JSP page. We can use JSP page directive session attribute to indicate compiler to not create session by default. It’s default value is true and session is created. To disable the session creation, we can use it like below.

    • <%@ page session=”false” %>

    33) What is difference between JspWriter and Servlet PrintWriter?

    Ans:

    Print Writer is the actual object responsible for writing the content in response. JspWriter uses the PrintWriter object behind the scene and provide buffer support. When the buffer is full or flushed, JspWriter uses the PrintWriter object to write the content into response.

    34) How can we extend JSP technology?

    Ans:

    We can extend JSP technology with custom tags to avoid scripting elements and java code in JSP pages.

    35) Provide some JSP Best Practices?

    Ans:

    Some of the JSP best practices are:

    • Avoid scripting elements in JSP pages. If JSP EL, action elements and JSTL not serve your needs then create custom tags.
    • Use comment properly, use JSP comments for code level or debugging purpose so that it’s not sent to client.
    • Avoid any business logic in JSP page, JSP pages should be used only for response generation for client.
    • Disable session creation in JSP page where you don’t need it for better performance.
    • Use page, taglib directives at the start of JSP page for better readability.
    • Proper use of jsp include directive or include action based on your requirements, include directive is good for static content whereas include action is good for dynamic content and including resource at runtime.
    • Proper exception handling using JSP error pages to avoid sending container generated response incase JSP pages throw exception in service method.
    • If you are having CSS and JavaScript code in JSP pages, it’s best to place them in separate files and include them in JSP page.
    • Most of the times JSTL is enough for our needs, if you find a scenario where it’s not then check your application design and try to put the logic in a servlet that will do the processing and then set attributes to be used in JSP pages.
    • Please let me know if I have missed any important JSP interview question, I will be adding more to the list in the future.
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    36)Explain JSP and tell its uses.

    Ans:

    JSP stands for Java Server Pages. It is a presentation layer technology independent of platform. It comes with SUN’s J2EE platforms. They are like HTML pages but with Java code pieces embedded in them. They are saved with a .jsp extension. They are compiled using JSP compiler in the background and generate a Servlet from the page.

    37) What is the requirement of a tag library?

    Ans:

    A collection of custom tags is called a Tag Library. Recurring tasks are handled more easily and reused across multiple applications to increase productivity. They are used by Web Application designers who focus on presentation rather than accessing database or other services. Some popular libraries are String tag library and Apache display tag library.

    38) Explain JSP Technology.

    Ans:

    JSP is a standard extension of Java and is defined on top of Servlet extensions. Its goal is to simplify management and creation of dynamic web pages. It is platform-independent, secure, and it makes use of Java as a server side scripting language.

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    39) Explain Implicit objects in JSP.

    Ans:

    Objects created by web container and contain information regarding a particular request, application or page are called Implicit Objects. They are :

    • response
    • exception
    • application
    • request
    • session
    • page
    • out
    • config
    • pageContext

    40) How can multiple submits due to refresh button clicks be prevented?

    Ans:

    Using a Post/Redirect/Get or a PRG pattern, this problem can be solved.

    • A form filled by the user is submitted to the server using POST or GET method. The state in the database and business model are updated.
    • A redirect response is used to reply by the servlet for a view page.
    • A view is loaded by the browser using the GET command and no user data is sent. This is safe from multiple submits as it is a separate JSP page.

    41) Is JSP technology extensible?

    Ans:

    Yes, JSP is easily extensible by use and modification of tags, or custom actions, encapsulated in tag libraries.

    42) Differentiate between response. Send Redirect(url) and <jsp:forward page = …> .

    Ans:

    • <jsp.forward> element forwards the request object from 1 JSP file to another. Target file can be HTML, servlet or another JSP file, but it should be in the same application context as forwarding JSP file.
    • sendRedirect send HTTP temporary redirect response to the browser. The browser then creates a new request for the redirected page. It kills the session variables.

    43) Can a subsequent request be accessed with one’s servlet code, if a request attribute is already sent in his JSP?

    Ans:

    • The request goes out of scope, thus, it cannot be accessed. However, if a request attribute is set in one’s servlet, then it can be accessed in his JSP.
    • A JSP is a server side component and the page in translated to a Java servlet, and then executed. Only HTML code is given as output.

    44)How to include static files in a JSP page?

    Ans:

    Static pages are always included using JSP include directive. This way the inclusion is performed in the translation phase once. Note that a relative URL must be supplied for file attribute. Although static resources may be included, it is not preferred as each request requires inclusion.

    45)  Why is it that JComponent have add() and remove() methods but Component doesn’t?

    Ans:

    JComponent is a subclass of Container. It contains other Components and JComponents.

    46) How can a thread safe JSP page be implemented?

    Ans:

    It can be done by having them implemented by the SingleThreadModel Interface. Add <%@page isThreadSafe=”false” %> directive in the JSP page.

    47) How can the output of JSP or servlet page be prevented from being cached by the browser?

    Ans:

    Using appropriate HTTP header attributes to prevent the dynamic content output by a JSP page from being cached by the browser.

    48) How to restrict page errors display in a JSP page?

    Ans:

    By setting up an “ErrorPage” attribute of PAGE directory to the name of the error page in the JSP page, and then in the error jsp page set “isErrorpage=”TRUE”, Errors can be stopped from getting displayed.

    49)What are JSP Actions?

    Ans:

    They are XML tags, which direct the server to using existing components or control behavior of JSP Engine. They consist of a typical prefix of “jsp:” and action name.

    • <jsp:include/>
    • <jsp:getProperty/>
    • <jsp:forward/>
    • <jsp:setProperty/>
    • <jsp:usebean/>
    • <jsp:plugin/>

    50) Differentiate between <jsp:include page=…> and <%@include file=…>.

    Ans:

    • Both these tags include information from 1 page to another.
    • The first tag acts as a function call between two Jsp’s. It is executed each time client page is accessed by the client. It is useful to modularize the web application. New content is included in the output.
    • The second tag content of file is textually embedded having similar directive. The changed content is not included in the output. It is helpful when code from one jsp is required by several jsp’s.

    51) Can constructor be used instead of init(), to initialize servlet?

    Ans:

    Yes, it is possible. But it is not preferred because init() was developed because earlier Java versions could not invoke constructors with arguments dynamically. So they could not assign a servletConfig. Today, however, servlet containers still call only no-arg constructor. So there is no access to servletContext or servletConfig.

    52) Explain lifecycle methods.

    Ans:

    • jsplnit(): The container calls this to initialize servlet instance. It is called only once for the servlet instance and preceded every other method
    • _jspService(): The container calls this for each request and passes it on to the objects. 
    • jspDestroy(): It is called by the container just before destruction of the instance.

    53) Explain JSP Output comments?

    Ans:

    They are comments that can be viewed in HTML Source File.

    54) Define Expression

    Ans:

    • Expression tag is used to insert Java values directly in the output. Its syntax is

    • <%=expression%>

    • It contains a scripting language expression that is evaluated, then converted to a string, and then inserted where the expression comes in JSP file.

    55) Define Composition.

    Ans:

    Composition has a stronger relationship with the object than Aggregation.

    56) Define JSP Scriptlet.

    Ans:

    It a JSP tag that encloses Java code in JSP pages. Their syntax is <% %>. Code written in scriptlet executes every time the program is run.

    57)  How can information from one JSP be passed to another JSP?

    Ans:

    The tag <Jsp:param> allows us to pass information between multiple Jsp’s.

    58) Explain the uses of <jsp:usebean> tag.

    Ans:

    • <jsp:useBean>
    • id=”beanInstName”
    • >
    • scope= “page | application”
    • class=”ABC.class”  type=”ABC.class”
    • </jsp:useBean>

    This tag creates an instance of java bean. It firstly tries to find if bean instance already exist and assign stores a reference in the variable. Type is also specified; otherwise it instantiates from the specified class storing a reference in the new variable.

    59)Explain handling of runtime exceptions.

    Ans:

    • Errorpage attribute is used to uncatch the run-time exceptions forwarded automatically to an error processing page.
    • It redirects the browser to JSP page error.jsp if any uncaught exception is faces during request handling. It is an error processing page.
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    60) Why does _jsp Service() start with an ‘_’ but other lifecycle methods do not?

    Ans:

    Whatever content made in a jsp page goes inside the _jspService() method by the container. If it is override, the compiler gives an error, but the other 2 lifecycles can be easily override. So ‘_’ shows that we cannot override this method.

    61) Explain the various scope values for <jsp:useBean> tag.

    Ans:

    <jsp:useBean> tag is used to use any java object in the jsp page. Some scope values are :

    • 1)application
    • 2)request
    • 3)page
    • 4)session

    62) Show the 2 types of comments in JSP.

    Ans:

    The 2 types are :

    • <%–JSP Comment–%>
    • <!–HTML comment–>

    63) Can Static method be Override?

    Ans:

    Ans: We can declare static methods with same signature in subclass, but it is not considered overriding as there won’t be any run-time polymorphism. Hence the answer is ‘No’.

    64) Explain JSP directives.

    Ans:

    JSP directives are messages to JSP Engine. They serve as a message from page to container and control the processing of the entire page. They can set global values like class declaration. They do not produce output and are enclosed in <%@….%>

    65) Explain pge Directives.

    Ans:

    Page Directives inform the JSP Engine about headers and facilities that the page receives from the environment. It is found at the top of all JSP pages. Its syntax is <%@ page attribute=”value”>

    66)Show attributes of page directives.

    Ans:

    • 1)Session : It shows if a session data is available to the page.
    • 2)Import : it shows packages that are imported.
    • 3)isELIgnored : It shows whether EL expressions are ignored when JSP translates into a servlet.
    • 4)contentType : it allows the user to specify the content type of page.

    67) What is Include directive?

    Ans:

    The include directive statically inserts the contents of a resource into the current JSP. It helps in the reuse of code without duplication. and includes contents of the file at translation time. Its syntax is as follows <%@ include file=”Filename”%>.

    68) What are standard actions in JSP?

    Ans:

    They affect overall runtime behaviour of a page and response sent to the client. They are used to include a file at request time, to instantiate a JavaBean or find one. They are also used to generate a browser-specific code or forward a request to a new page.

    69) Explain the jsp:setProperty action.

    Ans:

    It is used to give values to properties of beans that have been referenced beforehand.

    <jsp:useBean id=”ABC”…/> …

    <jsp:setProperty name=”ABC” property=”myProperty”…

    jsp:setproperty is executed even if a new bean is instantiated or existing bean is found.

    By adding </jsp.useBean> at the end of the code, the condition for execution is inverted i.e. It is not executed if existing object was found and only if a new object was instantiated.

    70) Define Static Block.

    Ans:

    It is used to start the static data member. It is executed before classloading.

    71) Explain jsp:plugin action.

    Ans:

    This action helps in insertion of a specific object in the browser or embed the element needed to specify the running of applet using Java plugin.

    72) Explain client and server side validation.

    Ans:

    Javascript is used for the client-side validation. It takes place within the browser. Javascript is used to submit the form data if validation is successful. Validation errors require no extra network trip because form cannot be submitted.

    Validation is also carried out in the server after submission. If validation fails, extra network trip is required to resend the form to the client.

    73) What is Translation Phase?

    Ans:

    JSP engine translates and compiles a JSP file to a servlet. This servlet moves to the execution phase where requests and responses are handled. They are compiled for the first time they are accessed unless manually compiled ahead of time. The manual or explicit compilation is useful for long and convoluted programs.

    74) Perform a Browser Redirection from a JSP Page.

    Ans:

    <% response.sendRedirect(URL); %>

    or we can change the location of the HTTP header attribute as follows:

    <% response.setStatus(HttpServletResponse.SC_MOVED_PERMANENTLY); response.setHeader(URL); %>

    75) Give uses of Object Cloning.

    Ans:

    Object cloning is used to create an exact copy of an object by typing the same code or using various other techniques.

    76) How to forward a request to another source.

    Ans:

    • <jsp:forward page=”/Page2.jsp” />

    77)How can Automatic creation of session be prevented in a JSP page?

    Ans:

    JSP page automatically create sessions for requests. By typing the following, it can be avoided.

    • <%@ page session=”false”  %>

    78)  How can you avoid scriptlet code in JSP?

    Ans:

    JavaBeans or Custom Tags can be used instead of scriptlet code.

    79) Explain the jspDestroy() method.

    Ans:

    Whenever a JSP page is about to be destroyed, the container invokes the jspDestroy() method from the javax.servlet.jsp.JspPage interface. Servlets destroy methods are similar to it. It can be easily overridden to perform cleanup, like when closing a database connection.

    80) Explain the <jsp:param> action.

    Ans:

    It is an action used with include or forward standard actions. It helps in passing the parameter names and values to a resource.

    81)  Explain static method.

    Ans:

    Ans: A static method is of the class and not the object of a class. It can be invoked without instance of a class. Static members can also access the static data and change its value.

    82)How to disable scripting?

    Ans:

    Scripting can be easily disabled by setting scripting-invalid element of the deployment descriptor to true. It is a sub-element of property group. Its can be false as well.

    83) Define JSP Declaration.

    Ans:

    JSP Declaration are tags used in declaring variables. They are enclosed in <%!%> tag. They are used in declaring functions and variables.

    • <%@page contentType=”text/html” %>
    • <html>
    • <body>
    • <%!
    • int a=0;
    • private int getCount()a++;return a;}
    • %>
    • <p>Values of a are:</p>
    • <p><%=getCount()%></p>
    • </body>
    • </html>

    84) How is JSP better than Servlet technology?

    Ans:

    JSP is a technology on the server’s side to make content generation simple. They are document centric, whereas servlets are programs. A Java server page can contain fragments of Java program, which execute and instantiate Java classes. However, they occur inside HTML template file. It provides the framework for development of a Web Application.

    85) Explain include Directive and include Action of JSP

    Ans:

    • This is a very popular interview question on JSP, which has been asked from a long time and still asked in the various interview. This question is good to test some fundamental concepts like the translation of JSP and the difference between translation time and run-time kind of concept.
    •  The syntax for include Directive is <%@ include file=”fileName” %> which means we are including some file to our JSP Page when we use include directive contents of an included file will be added to calling JSP page at translation time means when the calling JSP is converted to a servlet ,all the contents are added to that page.
    •  One important thing is that any JSP page has complied if we make any changes to that particular page but if we have changed the included file or JSP page the main calling JSP page will not execute again so the output will not be according to our expectation, this one is the main disadvantage of using the include directive that why it is mostly use to add static  resources, like Header and footer .
    • Syntax for include action is <jsp:include page=”relativeURL” /> it’s a runtime procedure means the result of the JSP page which is mentioned in relative URL is appended to calling JSP at runtime on their response object at the location where we have used this tag.  
    •          So any changes made to an included page are being effected every time, this is the main advantage of this action but only a relative URL we can use here , because request and response object is passed between calling JSP and included JSP. IF you want to learn more then you can also check JSP, Servlets and JDBC for Beginners: Build a Database App on Udemy. 

    86) Difference Between include Directive and include Action of JSP

    Ans:

    This JSP interview question is a continuation of the earlier question I just made it a separate one to write an answer in clear tabular format.

    • Include Directive
    • Include Action
    • include directive is processed at the translation time
    • Include action is processed at the run time.
    • include directive can use relative or absolute path
    • Include action always use relative path
    • Include directive can only include contents of resource it will not process the dynamic resource
    • Include action process the dynamic resource and result will be added to calling JSP
    • We can not pass any other parameter
    • Here we can pass other parameter also using JSP:param
    • We cannot  pass any request or response object to calling jsp to included file or JSP or vice versa
    • In this case it’s possible.
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    87)  Is it possible for one JSP to extend another java class if yes how?

    Ans:

    Yes it is possible we can extends another JSP using this <%@ include page extends=”classname” %> it’s a perfectly correct because when JSP is converted to servlet its implements javax.servlet.jsp.HttpJspPage interface, so for jsp page its possible to extend another java class . This question can be tricky if you don’t know some basic fact J, though it’s not advisable to write java code in jsp instead it’s better to use expression language and tag library.

    88) What is < jsp:usebean >tag why it is used.

    Ans:

    This was a very popular JSP interview question during early 2000, it has lost some of its shine but still asked now and then on interviews.

    JSP Syntax

    • <jsp:useBean
    •         id=”beanInstName”
    •         scope=”page | request | session | application”
    •             class=”package.class”    type=”package.class”
    • </jsp:useBean>

    This tag is used to create an instance of java bean, first of all, it tries to find out the bean if bean instance already exists assign stores a reference to it in the variable. If we specified the type, gives the Bean that type.otherwise instantiates it from the class we specify, storing a reference to it in the new variable.so jsp:usebean is a simple way to create a java bean.

    Example:

    • <jsp:useBean id=”stock” scope=”request” class=”market.Stock” />
    • <jsp:setProperty name=”bid” property=”price” value=”0.0″ />
    • a <jsp:useBean> element contains a <jsp:setProperty> element that sets property values in the Bean,we have <jsp:getProperty>element also to get the value from the bean.
    • Explanation of Attribute
    •  id=”beanInstanceName”

    A variable that identifies the Bean in the scope we specify. If the Bean has already been created by another <jsp:useBean> element, the value of id must match the value of id used in the original <jsp:useBean> element.

    • scope=”page | request | session | application”

    • The scope in which the Bean exists and the variable named in id is available. The default value is page. The meanings of the different scopes are shown below:
    • page – we can use the Bean within the JSP page with the <jsp:useBean> element
    • request – we can use the Bean from any JSP page processing the same request, until a JSP page sends a response to the client or forwards the request to another file.
    • session – we can use the Bean from any JSP page in the same session as the JSP page that created the Bean. The Bean exists across the entire session, and any page that participates in the session can use it..
    • application – we can use the Bean from any JSP page in the same application as the JSP page that created the Bean. The Bean exists across an entire JSP application, and any page in the application can use the Bean.
    • class=”package.class”

    Instantiates a Bean from a class, using the new keyword and the class constructor. The class must not be abstract and must have a public, no-argument constructor.

    type=”package.class”

    If the Bean already exists in the scope, gives the Bean a data type other than the class from which it was instantiated. If you use type without class or beanName, no Bean is instantiated.

    89) How can one Jsp Communicate with Java file.

    Ans:

    we have import tag <%@ page import=”market.stock.*” %> like this we can import all the java file to our jsp and use them as a regular class another way is  servlet can send  the instance of the java class to our  jsp and we can retrieve that object from the request obj and use it in our page.

    90) what are the implicit Objects in JSP?

    Ans:

    This is a fact based interview question what it checks is how much coding you do in JSP if you are doing it frequently you definitely know them. Implicit object is the object that is created by web container provides to a developer to access them in their program using JavaBeans and Servlets. These objects are called implicit objects because they are automatically instantiated.they are bydefault available in JSP page.

    They are request, response, pageContext, session, and application, out, config, page, and exception.

    91)  In JSP page how can we handle runtime exception?

    Ans:

    This is another popular JSP interview question which has asked to check how candidate used to handle Error and Exception in JSP. We can use the errorPage attribute of the page directive to have uncaught run-time exceptions automatically forwarded to an error processing page.

    Example: <%@ page errorPage=”error.jsp” %>

    It will redirect the browser to the JSP page error.jsp if an uncaught exception is encountered during request processing. Within error.jsp, will have to indicate that it is an error-processing page, using the directive: <%@ page isErrorPage=”true” %>

    92)Why is _jspService() method starting with an ‘_’ while other life cycle methods do not?

    Ans:

    main JSP life cycle method are jspInit() jspDestroy() and _jspService() ,bydefault whatever content we write in our jsp page will go inside the _jspService() method by the container if again will try to override this method JSP compiler will give error but we can override other two life cycle method as we have implementing this two in jsp so making this difference container use _ in jspService() method and shows that we cant override this method.

    93) How can you pass information from one jsp to included jsp:

    Ans:

    This JSP interview question is a little tricky and fact based. Using < Jsp: param> tag we can pass parameter from main jsp to included jsp page

    Example:

    • <jsp:include page=”newbid.jsp” flush=”true”>
    • <jsp:param name=”price” value=”123.7″/>
    • <jsp:param name=”quantity” value=”4″/>

    94)  what is the need of a tag library?

    Ans:

    tag library is a collection of custom tags. Custom actions helps recurring tasks will be handled more easily they can be reused across more than one application and increase productivity. JSP tag libraries are used by Web application designers who can focus on presentation issues rather than being concerned with how to access databases and other enterprise services. Some of the popular tag libraries are Apache display tag library and String tag library. You can also check my post on display tag library example on Spring.

    95) What is JSP?

    Ans:

    JSP stands for Java Server Pages, it is a server side technology which is used for creating dynamic web pages. It is the extension of servlets.

    Based on the above response, the interviewer may ask below follow-up questions:

    96) What does dynamic web page means here? 

    Ans:

    The web pages that are generated based on user’s response and may be different for each user are called dynamic web pages unlike the static web pages that are same for every user no matter how they interact with the application.

    97)What does Server side technology means? 

    Ans:

    There are basically two types of technologies: client-side and Server-side. Client-side means that the action takes place on the user’s (the client’s) computer. Server-side means that the action takes place on a web server (the place where you have stored all your JSP pages).

    98)What are JSP life cycle phases?

    Ans:

    Ans:  A JSP page goes through the below phases:

    • Compilation: In this phase the JSP code gets converted into the equivalent servlet code.
    • Initialization: The converted JSP code gets loaded into the memory. jspInit() method gets called in this phase.
    • Execution: _jspService() method gets called in this phase. In this step a response is generated for the user based on the request made by them.
    • Destroy: jspDestroy() method gets called in this phase to unload the JSP from the memory. This is also known as cleanup step.

    99) What all JSP lifecycle methods can you override in your JSP application?

    Ans:

    You can only override jspInit() and jspDestroy(), you cannot override the _jspService() method within a JSP page. By overriding jspInit() method you can initialize things like database connections, network connections etc. Whatever you initialize in jspInit() method can be freed up (released) in jspDestroy() method.

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