Java Jsp Interview Questions

1.Explain JSP life Cycle methods?

• jsp engine controls the life cycle of jsp
• Jsp life cycle is described by three life cycle methods and six life cycle phases

Jsp life cycle methods :

• jspInit()
• _jspService()
• jspDestroy()

• Jspinit() method is invoked when JSP page is initialized.
• The _jspService() method corresponds to the body of the jsp page.
• This method is defined automatically by the JSp container and should never be defined y the JSP page author.

Jsp Life cycle Phases: 

• Translation phase
• Compilation phase
• Instantiation phase
• initialization phase
• Servicing phase
• Destruction phase

Read More at : JSP Life Cycle

2. What are the Jsp Implicit Objects?

• Implicit objects in jsp are the objects that are created by the container automatically and the container makes all these 9 implicit objects to the developer.
• We do not need to create them explicitly, since these objects are created and automatically by container and are accessed using standard variables(objects) are called implicit objects.
• The following are of implicit variables available in the JSP.  

1. out
2. request
3. response
4. config
5. application
6. session
7. pagecontext
8. page
9. exception

Read More at: 9 Jsp Impicit Objects in java

3. Explain Jsp Scripting Elements?

• Jsp scripting elements are used to embed jva code in to the jsp.
• Jsp scripting elements are three types
  
  1. Declaration
  2. Expression
  3. Scriplet

Read More at: Jsp Scripting Elements

4. What are the Directives in Jsp?

• A jsp directive is a translation time instruction to the jsp engine.
• we have three kinds of directives.

1. Page directive
2. Include directive
3. Taglib directive

 Read More at: Jsp Directive Elements

 5. What are the differences between include directive and include action?

 

6. How to disable session in JSP?

• By using page directive
• <%@ page session="false" %> 

7. How can we handle exceptions in a JSP page?

• We can handle exception in jsp by using error page element of page directive 

• The errorPage attribute tells the JSP engine which page to display if there is an error while the current page runs.
  The value of the errorPage attribute is a relative URL.
  The following directive displays MyErrorPage.jsp when all uncaught exceptions are thrown
  

  Syntax:

  errorPage="url"
  

  Example:

  <%@ page errorPage="error.jsp"%>

8.How can we override jspInit() and jspDestroy() methods in a jsp?

• Both methods are executed once in a life cycle of a jsp.
• We can override these two method as shown below.
• <%!
      public void jspInit() {
          . . .
      }
  %>
• <%!    
      public void jspDestroy() {
          . . .   
      }
  %>

9.Can a JSP extend a java class?

• Yes we can extend a java class in jsp
• <%@ include page extends="classname" %>
• We can do this because jsp will convert to a servlet so a servlet can extend a class its fine

10.How can we pass information from one jsp to included jsp page?

• <jsp:include page="employeedetail.jsp" flush="true">
• <jsp:param name="name" value="abc"/>
• <jsp:param name="id" value="220"/>