How to script scala directly in JSP pages?

Question

Is there any scala JSP engine, or is there going to be any? i know about the scala web framework lift, but it seems more like tags. i am looking for a way to script like PHP.

thanks.

Answer 1

Edit: check http://scalate.fusesource.org/index.html: Scala Template Engine: like JSP without the crap but with added Scala coolness. I just stumbled upon this while checking the #scala twitter feed.

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You can have a look at http://github.com/alandipert/step. It looks like an active project with just enough to let you write Scala code mixed with xhtml code. Whether you can script like PHP, I don't know. One of the difference is that with JSP/PHP, you include a program inside an HTML page where as with step you include some xml into a Scala file.

There is going to be a bit of a learning curve with Scala and sbt but I think it's worth it to take advantage of Scala.

The other thing you can do is to write a custom JSP tag that lets you run some Scala code through the interpreter. I did a proof of concept and this seems to work:

/**
 * Proof of concept, you can run Scala code in a JSP tag.
 * Works with jetty and sbt.
 */
class ScalaScriptTag extends BodyTagSupport {

  override def doAfterBody():Int = {
    try { 
      val settings = new Settings(str => println(str))
      // interpreter classloader does not seem to pick up classes from the parent
      settings.classpath.value = 
        "lib_managed/compile/jsp-api-2.1-6.1.14.jar;" + 
        "lib_managed/compile/servlet-api-2.5-6.1.14.jar"
      var i = new Interpreter(settings) {
        override def parentClassLoader():ClassLoader = {
          return Thread.currentThread().getContextClassLoader();
        }
      }
      i.bind("pageContext", "javax.servlet.jsp.PageContext", pageContext)
      val source = Source.fromString(getBodyContent.getString)
      for (line <- source.getLines) { i.interpret(line) }
    } catch {
      case ioe: IOException => 
        throw new JspException(ioe.getMessage())
    }
    Tag.SKIP_BODY
  }

}                       

Answer 2

http://www.playframework.org/ has a scala mode. Play is very rails-ish. Might suit your needs.

Answer 3

Scalate is a Scala based template engine which allows you to use powerful Scala expressions instead of the limited JSP/JSF/JSTL EL expression language - while being completely statically typed so that templates are checked at edit/compile time for errors.

The Scaml templates in Scalate let you write really DRY emplates which are particularly good for XML/HTML (Rails fans tend to love Haml and Scaml is the Scala port of Haml).

Though if you like the JSP style of templates then you'd probably be better off starting with Ssp templates in Scalate which are JSP-like.