Elements of JSP (More JSP Constructs)
Scriptlets, contd.
Using Arrays
One can easily use scriptlets to loop over arrays. In this example, the user is presented with choice boxes. When s/he presses the submit button, the choices are displayed.
<HTML>
<BODY BGCOLOR="WHITE">
<FORM ACTION="choices.jsp">
<INPUT type="checkbox" name="music" value="Classical"> Classical<BR>
<INPUT type="checkbox" name="music" value="Rock"> Rock<BR>
<INPUT type="checkbox" name="music" value="Jazz"> Jazz<BR>
<INPUT type="checkbox" name="music" value="Blues"> Blues<BR>
<INPUT type="checkbox" name="music" value="DC-GoGo"> DC GoGo<BR>
<INPUT type="submit" value="Submit">
</FORM>
<%
String[] selected = request.getParameterValues("music");
if (selected != null && selected.length != 0) {
%>
You like the following kinds of music:
<UL>
<%
for (int i = 0; i < selected.length; i++) {
out.println("<LI>" + selected[i]);
}
%>
<UL>
<% } %>
</BODY>
</HTML>
Declarations
<%! some JAVA declarations %>
You can define variables and/or methods.
Example
The following JSP page illustrates the use of a counter variable as well as a method (that sets the color of text to arandom color) using the JSP declaration construct.
<HTML>
<BODY>
<%!
private int hitCount = 0;
String randomColor() {
java.util.Random random = new java.util.Random();
int R = (int) (random.nextFloat() * 255);
int G = (int) (random.nextFloat() * 255);
int B = (int) (random.nextFloat() * 255);
return "#" + Integer.toString(R, 16)
+ Integer.toString(G, 16)
+ Integer.toString(B, 16);
}
%>
<FONT COLOR="<%= randomColor() %>" >
This page has been accessed <%= ++hitCount %> times.
</FONT>
</BODY>
</HTML>
Summary of JSP Constructs
- Expressions
- Scriptlets
- Declarations
- Availability of pre-defined objects