Tomcat and Eclipse Zero Turnaround Deployment

Question

I want to be able to deploy code changes to Tomcat (near instantly), while I'm developing in Eclipse.

So far, I have my output from Eclipse placing the built classes in the WEB-INF/classes folder of my web application.

I also have a reloadable context, with the web.xml as a watched resource. Any edit / save to this file does reload my web app, taking just over one second - much quicker than building a new war file and deploying it in full.

However, what I'd like to do is trigger the redeploy when I edit any source file. As the .class files are being modified in Tomcat, it seems I just need to monitor any changes in the WEB-INF/classes folder and it's children.

I've read that I can add additional watched resources in Tomcat's context.xml but this doesn't seem to be quite what I need - unless it's possible to specify a directory that will be watched (including recursively monitoring sub folders and files)?

<Context>
  <WatchedResource>WEB-INF/web.xml</WatchedResource>
  <WatchedResource>WEB-INF/someother.file</WatchedResource>
  <Manager pathname=""/>
</Context>

So essentially, my question is can I watch the entire classes folder (without including each WatchedResource explicitly) to trigger a redeploy in Tomcat?

If not, can I configure Eclipse to touch the web.xml file, whenever I save a source file in that project? I'm developing on a Windows system. :(

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PS I'm not interested in the JRebel product. Any answer should be a free solution.

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Update

According to the Tomcat documentation, the classes folder should be monitored by setting the context to reloadable:

Set to true if you want Catalina to monitor classes in /WEB-INF/classes/ and /WEB-INF/lib for changes, and automatically reload the web application if a change is detected.

Only changes to the web.xml seem to trigger a reload. Is this a bug or is my setup incorrect?

Also, I've read about setting the docBase attribute for a given context:

docBase="webapps/someExample"

This appears to be close to what I need, as I could then republish in Eclipse quickly. My only problem is that I require several web apps / servlets to be running in Tomcat concurrently, on the same port etc.

Answer 1

For these cases I set the eclipse build output to WEB-INF/classes as you have done and create a context file with the docBase set to the webapp folder (parent of WEB-INF) in the project. This is manually placed in conf/Catalina/localhost (assuming default configs for some elements of server.xml). End result is tomcat ends up serving from the development directory. So, change a servlet or other class and it is updated to the classes folder. Save a jsp and it is immediately available.

If project structured like:

src
|-main
  |-webapp
    |-images
    |-js
    |-WEB-INF
      |-jsp
      |-classes

Then context would be like:

<?xml version="1.0" encoding="UTF-8"?>
<Context path="/path" reloadable="true" 
    docBase="<pathtoproject>/src/main/webapp" />

Answer 2

Maybe the Web Tools Project of Eclipse with auto-redeploy enabled will help you? Add a server, open properties and under Publishing you will see a radiobutton saying "Automatically publish when resources changes". This will result in a redeploy if classes changes otherwise just overwrites resources. You can install WTP via a built in update site (Eclipse only), so check out your software updates. It is free for most servers but it does not support certain Websphere features?

Answer 3

Try the Spring Loaded JVM agent I've described in the following answer: https://stackoverflow.com/a/37064672/1034436

While that has worked for my Spring web application, this should work with vanilla Eclipse + WTP + Tomcat + Dynamic Web Applications since Spring Loaded works on the JVM/classloading level.

You will still need to use the "Automatically publish when resources changes" as mentioned by @toomasr in his answer. However, you must also disable "Module auto reload by default" option as well. If you already added/published modules from Eclipse to Tomcat, then disable "Auto Reload" for each web module (via the Tomcat config page's Modules tab). That should prevent Tomcat from reloading the application when a single class file is updated, which I suspect is what all that reload/wait time is.