The Problems with JSP (JavaServer Pages)

Page II

Enter Template Engines

But why suffer the complexity of JSP just to do templating? Might it not be better to use a dedicated template engine? By using a template engine intended for this exact use instead of the general-purpose JSP, the underlying design can be cleaner, the syntax clearer, the error messages more meaningful, and the tool more customizable. Several companies have built such engines, the most popular probably being WebMacro (http://webmacro.org, from Semiotek) whose engine is free.

Using a dedicated template engine instead of JSP offers several technical advantages that developers should be aware of:

Problem #1: Java Code Too Tempting

JSP makes it tempting to put Java code in the Web page, even though that's considered bad design. Just as Java improves on C++ by removing the ability to use global variables and multiple inheritance, so do template engines improve on JSP by removing the ability to put raw code in the page. Template engines enforce good design.

Problem #2: Java Code Required

Doing mundane things in JSP can actually demand putting Java code in the page. For example, assume the page needs to determine the context root of the current Web application to create a link to the Web app home page:

In JSP this is best done using Java code:

<ahref="<%=request.getContextPath() %>/index.html">Home page</a>

You can try to avoid Java code using the <jsp:getProperty> tag but that leaves you with the following hard-to-read string:

<a href="<jsp:getProperty name="request"
property="contextPath"/>/index.html">HomePage</a>

Using a template engine there's no Java code and no ugly syntax. Here's the same command written in WebMacro:

<a href="$Request.ContextPath;/index.html">Home page</a>

In WebMacro, ContextPath is seen as a property of the $Request variable, accessed using a Perl-like syntax. Other template engines use other syntax styles.

As another example where JSP requires Java code in the page, assume an advanced "view" needs to set a cookie to record the user's default color scheme. a task that presumably should be done by the view and not the servlet controller. In JSP it requires Java code:

<% Cookie c = new Cookie ("colorscheme", "blue"); response.addCookie;%>

In WebMacro there's no Java code:

#set $Cookie.colorscheme = "blue"

As a last example, assume it's time to retrieve the color scheme cookie. For the benefit of JSP, we can presume also there's a utility class available to help since doing this raw with getCookies() is ridiculously difficult. In JSP:

<% String colorscheme = ServletUtils.getCookie (request, "colorscheme");%>

In WebMacro there's no need for a utility class and it's always:

$Cookie.colorscheme.Value

For graphics artists writing JSP pages, which syntax would be simpler to learn?

JSP 1.1 introduced custom tags (allowing arbitrary HTML-like tags to appear in JSP pages executing Java code on the back end) which may help with tasks like this, assuming there becomes a widely known, fully featured, freely available, standardized tag library. So far that has yet to occur.

Problem #3:Simple Tasks are Hard

Doing even a simple task such as header and footer includes is overly difficult with JSP. Assume there's a "header" template and a "footer" template to be included on all pages, and each template includes in its content the current page title.

In JSP the best way to do this is as follows:

<% String title = "The Page Title"; %>
<%@ include file="/header.jsp" %>
Your content here
<%@ include file="/footer.jsp" %>

Page creators must not forget the semicolon in the first line and must make sure to declare title as a Java String. Plus, the /header.jsp and /footer.jsp must be made publicly accessible somewhere under the document root even though they aren't full pages themselves.

In WebMacro including headers and footers is done easily:

#set $title = "The Page Title"
#parse "header.wm"
Your content here
#parse "footer.wm"

There are no semicolons or String types for designers to remember, and the .wm files are found in a customizable search path, not under the document root.

About the Author

Jason Hunter works as the Chief Technology Officer of K&A Software, where he specializes in Java training and consulting. He is author of Java Servlet Programming (O'Reilly) and publisher of the Web site http://www.servlets.com. He belongs to the working group responsible for Java Servlet API development and has made significant contributions to the Servlet API and reference implementation. He also writes columns for JavaWorld and speaks at conferences such as JavaOne, Software Development, Web Design & Development, and the SIGS JavaExpo.

Jason graduated summa cum laude from Willamette University (Salem, Oregon) in 1995 with a degree in Computer Science. After graduation, he worked at Silicon Graphics in Mountain View, CA, for several years, where he was responsible for developing (and breaking) all sorts of Web technologies.

TechMetrix Research is a technically focused analyst firm focused on e-business application development needs. Based in Boston, Mass., the firm publishes comparison reports and product reviews designed to aid enterprises with decision making and to keep pace with the fast-moving e-business market.

TechMetrix is a U.S.-based subsidiary of SQLI, a European company that offers on-site development services to international organizations. SQLI specializes in e-business project development.