Java Practical info : Introduction to Java Server Pages

JSP Components And First JSP Page

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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">                               This
post describes the components of a jsp page. My last post I try to given
introduction about jsp. This post some of the components I am introducing. And I
never used any of the components also I created first Hello world JSP page for understanding.
Later I can give each component based examples also. Please see simple video
end of the post.<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">                                A Jsp contains HTML content,jsp tags and java code. By using
jsp tags either we can embed java code directly into the jsp page or we can
invoke the functionality of java code running behind the scenes. Java code is
required for a jsp to provide dynamism to the web page.<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">Jsp tags can be classified into the following 3 categories.<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%; mso-bidi-font-family: Georgia; mso-fareast-font-family: Georgia;">1.<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">      
</span></span><span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">Scripting 
Elements<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%; mso-bidi-font-family: Georgia; mso-fareast-font-family: Georgia;">2.<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">     
</span></span><span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">Directives<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%; mso-bidi-font-family: Georgia; mso-fareast-font-family: Georgia;">3.<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">     
</span></span><span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">Actions<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><b>Scripting Elements:</b>- The basic functionality of scripting
elements is to allow jsp authors to embed java code directly into the jsp. We
can classify scripting elements as follows.<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%; mso-bidi-font-family: Georgia; mso-fareast-font-family: Georgia;">1.<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">      
</span></span><span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">Declaration<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%; mso-bidi-font-family: Georgia; mso-fareast-font-family: Georgia;">2.<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">     
</span></span><span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">Expression<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%; mso-bidi-font-family: Georgia; mso-fareast-font-family: Georgia;">3.<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">     
</span></span><span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">Scriptlet<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><b>Declaration:-</b> A Jsp declaration lets us define methods or
variables in jsp. These methods and variables become direct members of the
container generated servlet class. We can define both instance and static
members in a declaration. A declaration has the following form.<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><%!<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            //Java
Variable declarations and method definitions<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">%><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">For example<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><%!<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            Private int
count=1;//instance variable definition<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            Static int
total;//static variable declaration<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            Int getCount()//instance
method definition<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            {<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">                        Return
count;<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            }<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            Static int
getTotal()<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            {<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">                        Return
total;<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            }<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">Please see for better understanding JSP API click the following link</span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><a href="http://www.youtube.com/watch?v=PLPzCumtpyw">JSP API</a></span></div>
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JSP Components And First JSP Page

Image Source Google Images This post describes the components of a jsp page. My last post I try to gi...

Life Cycle of a JSP Page

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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">                           When a jsp is accessed for the first time, the server is
slower in responding. This is because, every jsp page must be converted into an
instance of a servlet class before it can be used to service client requests.
For each request, the JSP engine checks the time stamps of the source JSP page
and the corresponding Servlet class file to determine if the jsp page and the
corresponding servlet class file to determine if the jsp page is new or if it
has already been converted into class file. Therefore, if we modify a JSP page,
the whole process of converting the JSP page into servlet is performed again.
The process consists of the following phases known as life cycle phases.<o:p></o:p></span></div>
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<span style="font-family: "Courier New"; font-size: 12.0pt; line-height: 115%; mso-fareast-font-family: "Courier New";">o<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">  
</span></span><span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">Page Translation<o:p></o:p></span></div>
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<span style="font-family: "Courier New"; font-size: 12.0pt; line-height: 115%; mso-fareast-font-family: "Courier New";">o<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">  
</span></span><span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">Page Compilation<o:p></o:p></span></div>
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<span style="font-family: "Courier New"; font-size: 12.0pt; line-height: 115%; mso-fareast-font-family: "Courier New";">o<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">  
</span></span><span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">Generated Servlet class loading<o:p></o:p></span></div>
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<span style="font-family: "Courier New"; font-size: 12.0pt; line-height: 115%; mso-fareast-font-family: "Courier New";">o<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">  
</span></span><span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">Servlet instantiation phase<o:p></o:p></span></div>
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</span></span><span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">Calling jspInit() known as initialization phase<o:p></o:p></span></div>
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<span style="font-family: "Courier New"; font-size: 12.0pt; line-height: 115%; mso-fareast-font-family: "Courier New";">o<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">  
</span></span><span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">Calling _jspService() known as servicing phase<o:p></o:p></span></div>
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</span></span><span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">Calling jspDestroy() known as destruction phase<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><b>Translation phase:</b> During this phase , the jsp engine reads
the hsp page, parses it and validates the syntax of the tags, once the
validations are completed, the engine creates the java source code that
contains public servlet class.<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><b>Compilation phase:</b> In this phase, the java compilation unit
generated in the previous phases is compiled. The result of this compilation is
the class file of the container generated servlet.<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><b>Instantiation phase:-</b> The serlvet class is loaded
dynamically and the servlet engine creates the servlet instance.<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><b>Life cycle methods of ajsp:</b> container generated servlet implements
 javax.servlet.Servlet interface. jspPage
interface declares 2 methods.<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            JspInit()<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            JspDestroy()<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">HttpJspPage interface declares one method that serves the
Http Client requests.<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            jspServlice()<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">These methods are known as life cycle methods of a Jsp.<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><b>Initialization Phase:</b> The container calls this method to initialize
the servlet instance.<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">Servicing Phase:- In this phase _jspService() method is
called by the container every time request 
comes to the jsp.<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><b>Destruction Phase:-</b> Whe the container is instructed to take
the servlet instance out of service, before the instance is sent for garbase
collection, container calls the life cycle method jspDestroy().<o:p></o:p></span></div>
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     <span style="font-family: Georgia, Times New Roman, serif;">please see for better understanding some people may read or some people may see better understanding that's the reason i am giving every post one video. at least you can see the following video you can understand better way of this post.</span></div>
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<span style="font-family: Georgia, Times New Roman, serif;">Please click this link <a href="https://www.youtube.com/watch?v=SIteMzG767M">Life Cycle of JSP page</a></span></div>
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Life Cycle of a JSP Page

When a jsp is accessed for the first time, the server is slower in responding. This is because, every js...