In previous post we are sharing Declaration some of
important point I am coding here also please see my attached video also for
better understanding.
o
In a declaration we can define (rarely) a static
block and a class also
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In a Jsp we can have any number of declarations
in any order.
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Variables declared in a declaration are
initialized to java default values.
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Variables in a declaration retain their values
across multiple requests because they are created
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And initialized only once.
Expression:- An expression scripting element is an embedded
java expression that is evaluated and converted to a text string. The resulting
text string is placed in a jsp output, in the location at which the element
appears. Expressions act as placeholders for java anguage expressions. An
expression is evaluated each time the page is accessed, and its value is then
embedded in the output HTML. An expression has the following form.
<%=any
vaid java expression %>
Examples:
<%=a+b %>
<%=new java.util.Date()%>
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Expressions are inserted into the service method
of the container- generated servlet.
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We can have any number of expressions per page.
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Embedded java expression should not be
terminated with a semicolon.
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We can print the value of any object or ay
primitive data type to the output steam using an
expression.
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We can also use an expression in a jsp action
attribute. In this case the value of the ex-Precision
does not go to the output stream. It is evaluated at request time, and its
value is assigned to the attribute. An Expression used in this way is known as
request time attribute expression.
Scriptlet:- A scriptlet is used to include complete
fragments of java code in the body of the JSP page. This scripting element
differs from the other two in 2ways.
- It is not limited to the declaration of methods and variables.
- It does not generated a string output directly, as expressions do.
A scriptlet has the following form <% Any vakud free frin
if hava cide %>
For example,
<% int sum=0;
For(int
I=1;i<10;i++)
Sum+=1;
%>
o
Scriptlet can be placed anywhere within the jsp
body
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We can place any number of scriptlets in a jsp.
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Each scriptlet is inserted into the service
method of the container – generated servlet in the given order.
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The scriptlet is executed each time the page is
requested.
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As scriptlets contain any java code, they are
typically used for embedding computing logic within a jsp page.
Comments in a JSP page
In a jsp we can have 3 kinds of comments
Java
comments
HTML
comments
JSP
comments
In a declaration or a scriplet we can have single line or
multi line java comments. HTML comment is of the form <!—Any commenting text
à
A JSP comment is of the form <%-- Any commenting text
--%>
Note:- A JSP comment is also known as a hidden comment as it
is not displayed in the client.
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