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JSP tutorial part 14:Difference Between Include Directive and Include action

Difference Between Include Directive and Include action

include Directive:
— At JSP page translation time, the content of the file given in the include directive is ‘pasted’ as it is, in the place where the JSP include directive is used.
 Then the source JSP page is converted into a java servlet class.
The included file can be a static resource or a JSP page.
 Generally JSP include directive is used to include header banners and footers.
 — The source JSP page gets compiled only if that page has changed.
 — If there is a change in the included JSP file, the source JSP file will not be compiled and therefore the modification will not get reflected in the output.
Include Action:
<jsp:include page= "index.jsp“>
The jsp:include action element is like a function call. At runtime, the included file
will be ‘executed’ and the result content will be included with the source JSP page.
When the included JSP page is called, both the request and response objects are
passed as parameters.
If there is a need to pass additional parameters, then jsp:param element can be
used.
Note : If the resource is static, its content is inserted into the calling JSP file, since
there is no processing needed.
Invoking a Servlet from a JSP Page
As when invoking one JSP page from another, you can invoke a servlet from a
JSP page through the jsp:include and jsp:forward action tags.
·          Following is an example:
<jsp:include page="/servlet/MyServlet" flush="true" />
·          When the servlet has finished executing, control is transferred back to the JSP
page and the page continues executing.
·          The following statement clears the page buffer, terminates the execution of the
JSP page, and executes the servlet:
·          <jsp:forward page="/servlet/MyServlet" />
·
In reality, It is other way , i.e. A servlet that acts as a controller invokes JSP
Alternatively, you can pass data between a JSP page and a servlet through an appropriately scoped Java Bean or through attributes of the HTTP request object.
Calling a servlet from a JSP- html form action
<FORM METHOD="POST|GET" ACTION="application_URL/JSP_URL">
<!-- Other tags such as text boxes and buttons go here -->
</FORM>
Calling a servlet from a JSP – jsp:forward
Invoking a servlet from a JSP directly through the jsp:include or jsp:forward tags.
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Call the servlet through jsp:forward tag</title>
</head>
<body>
<p> Calling Servlet from JSP </p>
<jsp:forward page=“/JSPProject/CounterServlet"></jsp:forward>
</body>
Invoking a JSP from a JSP
To invoke a JSP file from another JSP file, you can perform one of the following:
•Specify the URL of the second JSP file on the FORM ACTION attribute:
<FORM action=“JSP_URL">
……
</FORM>
•Specify the URL of the second JSP file in an anchor tag HREF attribute:
<a href="JSP_URL"> reference-text </a>

•Using <jsp:forward > or <jsp:include> action tags.

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