This tutorial will explain how to use both expressions and scriptlets to put dynamic content within your jsp pages.
Expressions:
Expressions provide the ability to include simple java within your page that is evaluated at run time with the result being output to the page. The character sequences <%= and %> to enclose Java expressions. Examples 1 and 2 from the source code below demonstrate this below.
1. Having an expression print the current date using java.util.Date()
Date:<%= new java.util.Date() %>2
2. Having an expression print “Hello World!” from a java String called helloWorld
<% String helloWorld = "Hello World!"; %> <%= helloWorld %> <br>
Scriplets:
For more complicated java, scriptlets can be used. Scriplets provide more complicated blocks of java code to be inlucded within the page. Example 2 above shows a scriptlet created a local variable called helloWorld. Examples 4 and 5 demonstrate this further below.
3. Having an expression print true or false when comparing variables on the server side from a previous scriptlet code block.
<% String result = "false"; int a = 1; int b = 1; int c = 2; if (a==b){ result = "true"; }; %> a(<%=a %>)==b(<%=b %>) = result<br> result-> <%= result %> <br> <% String result2 = "false"; if (a==c){ result2 = "true"; }; %> a(<%=a %>)==c(<%=c %>) = result2<br> result2-> <%= result2 %> <br> <br>
4. Using the out variable to have the scriplet generate HTML. (using out, the output will appear in the HTML page. In the below exampl, you should see “out – test” displayed in the html)
<% out.println("out - test"); %>
5. Using the System.out variable to have the scriptlet gerneate console outs. (using System.out, the output will appear within the eclipse console. In the below example, you should see “System.out – test appear in the eclipse console.” )
<% System.out.println("System.out - test"); %>