Working with JSP action Tags:
Action tags are a set of some basic tags,
such as inserting other page resources, forwarding the request to another page,
creating and locating the JavaBeans instances, and setting and retrieving bean
properties, in JSP pages. Instead of using Java code, the programmer uses
special JSP action tags to either link to a Java Bean set its properties, or get
its properties.
These are the most commonly used action
tags are :
- include
- forward
- param
- useBean
- setProperty
- getProperty
In this article I described the first three action
tags, the next three action tags will be described in the next article.
Describing the Include Tag: The include
action tag allows a static or dynamic resource such as HTML or JSP pages,
specified by a URL, to be included in the current JSP while processing a
request.Include action tag is almost similar to include directive. This include
can be static or dynamic. This include file is first compiled and output of this
file is inserted with parent file. The following code snippet shows the syntax
of the include action :
<jsp: include attributes>
<!--zero or more jsp: param tags-->
</jsp: include>
Difference Between Include Directive and
Include action:
Include Directive: The 'include'
directive tag inserts the given page and includes content in the generated
Servlet page during the translation phase of the JSP life cycle. It is generally
used to include files, such as HTML, JSP, XML .txt file, into a JSP page
statically. The snippet code use for it is:
<%@ include file= "index.jsp" %>
Include Action: The 'include' action tag
is used to include the response generated by executing the specified JSP page or
Servlet. Unlike the include directive tag, the include action tag accepts
expressions. we can decide the page to be included at runtime, whereas it
is not possible with the include directive tag. The snippet code use for it is:
<jsp: include page= "index.jsp">
Describing the Forward Tag: The
jsp:forward tag forwards the request to another resource. The resource can be
dynamic or static. When we use param tags, it is dynamic forward
with having values. Static forward is simple forward without having param tags.
Forward is used when we need to jump from one page to another if error occur or
if work is completed in parent page. The following
code snippet shows the syntax of the forward action:
<jsp:forward attributes>
<!--zero or more jsp: param tags-->
</jsp:forward>
Like:<jsp:forward page= "Header.html"/>
Describing the Param Tag: The jsp:param
tag allows us to a name and value pair as parameter to a dynamic resource,
while including and forwarding the jsp page to another jsp page. we can
use more than one param tag if we want to more than one parameter. The
following code snippet shows the syntax of the param action :
<jsp:param attributes />
Example: In this example i use the
functionality of the discussed action tags:
index.jsp:
<Html>
<body bgcolor="skyblue">
<pre>
<form action="front.jsp">
<b>Number 1:</b><input type="text" name="f1"/>
<b>Number 2:</b><input type="text" name="f2"/><br><br>
<input type="submit" name="submit" value="Add"/><input type="submit"
name="submit" value="Sub"/>
</form>
</pre>
</body>
</Html>
Front.jsp:
<%@page errorPage="/index.jsp" %>
<%
String s1=request.getParameter("f1");
String s2=request.getParameter("f2");
Integer.parseInt(s1);
Integer.parseInt(s2);
String submit=request.getParameter("submit");
if(submit.equals("Add")){
%>
<jsp:forward page="/Add.jsp"/>
<%
} else if(submit.equals("Sub")){
%>
<jsp:forward page="/Sub.jsp"/>
<%
} else{
%>
<jsp:forward page="/index.jsp"/>
<%}%>
Add.jsp:
<%
int a1=Integer.parseInt(request.getParameter("f1"));
int a2=Integer.parseInt(request.getParameter("f2"));
int result=a1+a2;
%>
<jsp:forward page="/Result.jsp">
<jsp:param name="result" value="<%=result%>"/>
</jsp:forward>
Sub.jsp:
<%
int a1=Integer.parseInt(request.getParameter("f1"));
int a2=Integer.parseInt(request.getParameter("f2"));
int result=a1-a2;
%>
<jsp:forward page="/Result.jsp">
<jsp:param name="result" value="<%=result%>"/>
</jsp:forward>
Result.jsp:
<%
String result=request.getParameter("result");
String submit=request.getParameter("submit");
%>
<html>
<body bgcolor="cyan">
<center>
<%
if(submit.equals("Add")){
%>
Result of Addition:<%=result%>
<%
}else{
%>
Result of Subtraction:<%=result%>
<%}%>
</center>
<jsp:include page="/index.jsp"/>
</body>
</html>
Output:
index.jsp:
![index..gif]()
Result.jsp:
Addition
![result1.gif]()
Subtraction
![result2.gif]()