JSP Expressions tag

This tag is used to give some java expression(only Expression within one tag)The Expression given in the expression tag is evaluated and then printed on the browser

Syntax:

<%=expression %>expression

Note:

The Expression should not be ended with the';'
Example application explanation:
JSP simply puts java inside HTML pages.


We can take any existing HTML page and change its exrtension to ".jsp" insted of ".html". what happens behind the scenes is that our JSP is being turned into a java file,complied and loaded.
this compilation only happens once, so after the first load,the file dosen't take long time to load anymore(But every time you change the JSP file,it will be re-translated abd re-compiled again.)

A JSP expression is used to insert the value of a scripting language expression, converted into a string, into the data stream returned to the client.
When the scripting language is the Java programming language, an expression is transformed into a statement that converts the value of the expression into a String object and inserts it into the implicit out object.


Adding dynamic content via expression

The character sequences<%= and %>enclose Java expression,which are evaluated at run time. This is what makes it possible to use JSP to generat dynamic HTML pages that changes in response to user action or vary from user to user.

jsexpression.jsp

    
    
    
    Hello world<%= new java.util.Date() %>
The syntax for an expression is as follows:

<%= scripting-language-expression %>

Note that a semicolon is not allowed within a JSP expression, even if the same expression has a semicolon when you use it within a scriptlet.

Syntax:

<%=expression %>expression

Note: The Expression should not be ended with the';'

In the web service version of the hello1 application, response.jsp contains the following scriptlet, which gets the proxy that implements the service endpoint interface. It then invokes the sayHello method on the proxy, passing the user name retrieved from a request parameter:

<%

String resp = null;

try {

Hello hello = new HelloService().getHelloPort();

resp = hello.sayHello(request.getParameter("username"));

} catch (Exception ex) {

resp = ex.toString();

}

%>

A scripting expression is then used to insert the value of resp into the output stream:

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