Struts to Groovy – Migrating a Struts/JSP Application

grailsgroovyjspstruts

I have taken over development of a JSP/Struts application. Right now it's a bit of a mess, and I'm finding the JSP pages with Struts tags to be insanely verbose. Has anyone migrated a Struts application to Groovy/Grails? Can it be done incrementally, page by page?

@4bu3li: I was thinking of replacing the JSPs one by one with Groovy HTML builder code. IMO struts tags are a masterpiece of verbosity and obfuscation, and I'm tired of matching open and close tags. Right now the team is just me and one other guy, and I know Groovy better than I know JSPs and Struts. We are reworking the entire site, so it's all going to be rewritten somehow. But I can't stop maintenance, so I need to incrementally rewrite it page by page. Could I just start reworking Struts action methods to return Groovy-generated content?

Best Answer

I haven't used Struts for ages, but Struts by default can render Velocity markup, FreeMarker, as well as JSP (maybe other formats too).

For example, to render FreeMarker pages, your action definitions would look like this:

<action name="test" class="com.acme.TestAction">
    <result name="success" type="freemarker">test-success.ftl</result>
</action>

I assume you should be able to use a custom type to render GSP or builder code.

UPDATE:

Here it is explained how to create Struts 2 actions using Groovy.

Related Solutions

Java – How to debug a JSP

There are several options that can help you:

This answer actually explains how to debug JSPs specifically: https://stackoverflow.com/questions/33739/jsp-debugging-in-intellij-idea. I haven't ever tried this so I followed the next three suggestions when I was using JSP, JBoss, and IntelliJ...
Remember that JSPs are compiled to classes. When it says line 702, it means in the compiled class. If you have test.jsp, the class name is probably test_jsp, so open your JBoss work directory and search for test_jsp.java (once you find the right directory, you'll see that the directory structure matches your JSP directory structure). Whenever I had a JSP exception I could find the line quite easily and usually match it up to the corresponding line in the JSP.
Breakpoints work just fine in Java classes called from a JSP. So, maybe you can move the Java script code that you have in your JSP into a class and debug from the entry point. In the future you can also make a habit of rearranging your logic so that the majority of it is in a class that is being called from the JSP, and the JSP is simple, straightforward and hopefully not throwing any exceptions. This is good practice anyway.
Better yet, remove all (or virtually all) Java logic into Java classes, leaving JSPs for HTML and JSP tags. I know this isn't feasible right away, but again, it's a good idea long term to avoid problems like this.

Hibernate Sessions – Best Way to Manage Hibernate Sessions in a Struts-1 Application

I don't think struts 1 ships with an OpenSessionInView filter, but one way to manage sessions is opening sessions on a per-request basis, which are then accessed via the thread local pattern.

This will keep the session open until the request is done rendering, meaning you can use lazily instantiated collections in your views safely.

Spring ships with an opensessioninview filter, here is an article on how to use it, or, it's relatively straightforward to write your own as a standard servlet filter.

to write your own, you would write ServletFilter that implements Filter, and implement a doFilter method. it would look something like:

void doFilter(ServletRequest req,ServletResponse res,FilterChain chain) {
   Session session;
   try {
      session = // get my hibernate session here
      // do the request
      chain.doFilter(req, res);
   } catch (Whatever) {
   } finally {
     // close my session here
   }

you would need to register this filter in your web.xml, and apply it to the URLs that you need sessions with. This is not the most elegant solution in the world, but it does work just fine.