Interview Material

JSP Interview Questions Answers

JSP Interview Question - 61 : -

What is JSP?

JSP Interview Answer - 61 : -

Let's consider the answer to that from two different perspectives: that of an HTML designer and that of a Java programmer.
If you are an HTML designer, you can look at JSP technology as extending HTML to provide you with the ability to seamlessly embed snippets of Java code within your HTML pages. These bits of Java code generate dynamic content, which is embedded within the other HTML/XML content you author. Even better, JSP technology provides the means by which programmers can create new HTML/XML tags and JavaBeans components, which provide new features for HTML designers without those designers needing to learn how to program.
Note: A common misconception is that Java code embedded in a JSP page is transmitted with the HTML and executed by the user agent (such as a browser). This is not the case. A JSP page is translated into a Java servlet and executed on the server. JSP statements embedded in the JSP page become part of the servlet generated from the JSP page. The resulting servlet is executed on the server. It is never visible to the user agent.
If you are a Java programmer, you can look at JSP technology as a new, higher-level means to writing servlets. Instead of directly writing servlet classes and then emitting HTML from your servlets, you write HTML pages with Java code embedded in them. The JSP environment takes your page and dynamically compiles it. Whenever a user agent requests that page from the Web server, the servlet that was generated from your JSP code is executed, and the results are returned to the user.

JSP Interview Question - 62 : -

In the Servlet 2.4 specification SingleThreadModel has been deprecated, why?

JSP Interview Answer - 62 : -

Because it is not practical to have such model. Whether you set isThreadSafe to true or false, you should take care of concurrent client requests to the JSP page by synchronizing access to any shared objects defined at the page level.

JSP Interview Question - 63 : -

How many messaging models do JMS provide for and what are they?

JSP Interview Answer - 63 : -

JMS provide for two messaging models, publish-and-subscribe and point-to-point queuing.

JSP Interview Question - 64 : -

How does JSP handle run-time exceptions?

JSP Interview Answer - 64 : -

You can use the errorPage attribute of the page directive to have uncaught runtime exceptions automatically forwarded to an error processing page.
For example:
redirects the browser to the JSP page error.jsp if an uncaught exception is encountered during request processing. Within error.jsp, if you indicate that it is an error-processing page, via the directive:
the Throwable object describing the exception may be accessed within the error page via the exception implicit object.
Note: You must always use a relative URL as the value for the errorPage attribute.

JSP Interview Question - 65 : -

How do I mix JSP and SSI #include?

JSP Interview Answer - 65 : -

1
If you're just including raw HTML, use the #include directive as usual inside your .jsp file.
But it's a little trickier if you want the server to evaluate any JSP code that's inside the included file. If your data.inc file contains jsp code you will have to use
The is used for including non-JSP files.

2
If you're just including raw HTML, use the #include directive as usual inside your .jsp file.

But it's a little trickier if you want the server to evaluate any JSP code that's inside the included file. Ronel Sumibcay (ronel@LIVESOFTWARE.COM) says: If your data.inc file contains jsp code you will have to use
<%@ vinclude="data.inc" %>
The  is used for including non-JSP files.

JSP Interview Question - 66 : -

How many JSP scripting elements and what are they?

JSP Interview Answer - 66 : -

There are three scripting language elements:
--declarations
--scriptlets
--expressions

JSP Interview Question - 67 : -

What is difference between custom JSP tags and beans?

JSP Interview Answer - 67 : -

Custom JSP tag is a tag you defined. You define how a tag, its attributes and its body are interpreted, and then group your tags into collections called tag libraries that can be used in any number of JSP files. To use custom JSP tags, you need to define three separate components:
1. the tag handler class that defines the tag\'s behavior
2. the tag library descriptor file that maps the XML element names to the tag implementations
3. the JSP file that uses the tag library
When the first two components are done, you can use the tag by using taglib directive:
<%@ taglib uri="xxx.tld" prefix="..." %>
Then you are ready to use the tags you defined. Let's say the tag prefix is test:
MyJSPTag or
JavaBeans are Java utility classes you defined. Beans have a standard format for Java classes. You use tags to declare a bean and use to set value of the bean class and use to get value of the bean class.

<%=identifier.getclassField() %>
Custom tags and beans accomplish the same goals -- encapsulating complex behavior into simple and accessible forms. There are several differences:
Custom tags can manipulate JSP content; beans cannot.
Complex operations can be reduced to a significantly simpler form with custom tags than with beans. Custom tags require quite a bit more work to set up than do beans.
Custom tags usually define relatively self-contained behavior, whereas beans are often defined in one servlet and used in a different servlet or JSP page.
Custom tags are available only in JSP 1.1 and later, but beans can be used in all JSP 1.x versions.

JSP Interview Question - 68 : -

How do I include static files within a JSP page?

JSP Interview Answer - 68 : -

Static resources should always be included using the JSP include directive. This way, the inclusion is performed just once during the translation phase.
The following example shows the syntax:
< % @ include file="copyright.html" % >
Do note that you should always supply a relative URL for the file attribute. Although you can also include static resources using the action, this is not advisable as the inclusion is then performed for each and every request.
How do I have the JSP-generated servlet subclass my own custom servlet class, instead of the default? One should be very careful when having JSP pages extend custom servlet classes as opposed to the default one generated by the JSP engine. In doing so, you may lose out on any advanced optimization that may be provided by the JSPengine.
In any case, your new super class has to fulfill the contract with the JSP engine by: Implementing the HttpJspPage interface, if the protocol used is HTTP, or implementing JspPage otherwise Ensuring that all the methods in the Servlet interface are declared final.
Additionally, your servlet super class also needs to do the following:
The service() method has to invoke the _jspService() method
The init() method has to invoke the jspInit() method
The destroy() method has to invoke jspDestroy()
If any of the above conditions are not satisfied, the JSP engine may throw a translation error. Once the super class has been developed, you can have your JSP extend it as follows: