Friday, November 26, 2004

Some cool stuff about JSP 2.0

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:
         <head><title>JSP 2.0 new features</title></head>
           Hello ${}
    Find more about JSP 2.0 Expression Language in the J2EE 1.4 tutorial.
  • Easy tags creation with .tag files
    It is now easier to create your own tags.
    You just need to create a new .tag file (or .tagx if you want to use XML syntax) in the WEB-INF/tags directory of your Web application; or META-INF/tags if you want to package the Tags in Jar file. So creating a .tag file is easy, using the attribute directive. The following example is a new tag named mytag.tag that prints a title set using the attribute title, in the color specified in the attribute textColor.
    <%@ attribute name="title" required="true" description="Title of the document"%>
    <%@ attribute name="textColor" required="true" description="Color of the Title"%>
    <h1 style="color:${textColor}">${title}</h1>
    Here is the JSP that uses this new Tag:
    <%@ taglib tagdir="/WEB-INF/tags/" prefix="tags"%>
          <tags:mytag title="My new JSP" textColor="blue"/>
          Hello World${}
  • Easy header and footer template using the prelude and coda includes:
    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:
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.

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