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Some cool stuff about JSP 2.0

· 3 min read

J2EE 1.4 introduces a major release of JSP: 2.0.

Here some of the cool new features:

Direct usage of Expression Language (EL) in your JSP​

You do not need to put the EL in any tag now, just use it as needed:

<html>
<head><title>JSP 2.0 new features</title></head>
<body>
Hello ${param.name}
</body>
</html>

Find more about JSP 2.0 Expression Language in the J2EE 1.4 tutorial.

Easy tags creation with .tag files​

It is now easier to create your own tags. You just need to create a new .tag file (or .tagx if you want to use XML syntax) in the WEB-INF/tags directory of your Web application; or META-INF/tags if you want to package the Tags in Jar file. So creating a .tag file is easy, using the attribute directive. The following example is a new tag named mytag.tag that prints a title set using the attribute title, in the color specified in the attribute textColor.

<%@ attribute name="title" required="true" description="Title of the document"%>
<%@ attribute name="textColor" required="true" description="Color of the Title"%>
<h1 style="color:${textColor}">${title}</h1>

Here is the JSP that uses this new Tag:

<%@ taglib tagdir="/WEB-INF/tags/" prefix="tags"%>
<html>
<head>
</head>
<body>
<p>
<tags:mytag title="My new JSP" textColor="blue"/>
</p>
<p>
Hello World${param.name}
</p>
</body>
</html>

In most of the Web application that I have built, I started by creating template for my HTML pages; most of them to handle header and footer. Oracle JSP implementation provides this for a while using the Global Include feature. JSP 2.0 introduces a standard way of doing that using prelude and coda includes. I hate the choice made by the spec to call that prelude and coda. May be good Java developer are necessary musicians, since this is commonly used there? Why not simply header/footer or using a prefix like pre.../post.... Anyway, that is not the point.

The way you can set a prelude and/or coda include to your JSPs is done with the new Web Descriptor tag: <jsp-property-group>. This new tag allows you to configure a set of JSP that matches a specific URL. Part of the subtags of <jsp-property-group> are:

  • <include-coda> : the path to JSP fragment (.jspf) to include in the beginning all the JSP that matched the URL.
  • <include-prelude>:the path to the JSP fragment to include in the end all the JSP that matched the URL.

An example configuration:

<jsp-config>
<jsp-property-group>
<url-pattern>*.jsp</url-pattern>
<include-prelude>/WEB-INF/includes/prelude.jsp</include-prelude>
<include-coda>/WEB-INF/includes/coda.jsp</include-coda>
</jsp-property-group>
</jsp-config>

This 3 new features of JSP 2.0 are just a very small list of the features introduced in JSP and Servlet in J2EE 1.4, but are my favorites. They are very easy to test and to adopt.