Home » Java » Enterprise Java » Change Without Redeploying With Eclipse And Tomcat

About Bozhidar Bozhanov

Bozhidar Bozhanov
Senior Java developer, one of the top stackoverflow users, fluent with Java and Java technology stacks - Spring, JPA, JavaEE, as well as Android, Scala and any framework you throw at him. creator of Computoser - an algorithmic music composer. Worked on telecom projects, e-government and large-scale online recruitment and navigation platforms.

Change Without Redeploying With Eclipse And Tomcat

They say developing Java is slow because of the bloated application servers – you have to redeploy the application to see your changes. While PHP, Python, etc. scripting languages, allow you to “save & refresh”. This quora question summarizes that “myth”.

Yup, it’s a myth. You can use “save & refresh” in java web applications as well. The JVM has the so-called HotSwap – replacing classes at runtime. So you just have to start the server in debug mode (the hotswap feature is available in debug mode) and copy the class files. With eclipse that can be done in (at least) two ways:

  • WTP – configure the “Deployment Assembly” to send compiled classes to WEB-INF/classes
  • FileSync plugin for eclipse – configure it to send your compiled classes to an absolute path (where your tomcat lives)

I’ve made a more extensive description of how to use them in this stackoverflow answer.

Now, of course, there’s a catch. You can’t swap structural changes. If you add a new class, new method, change the method arguments, add fields, add annotations, these can’t be swapped at runtime. But “save & refresh” usually involves simply changing a line within a method.

Structural changes are more rare, and in some cases mean the whole application has to be re-initialized anyway. You can’t hotswap configuration as well – your application is usually configured in some (.xml) file, so if you change it, you’d have to redeploy. But that, again, seems quite an ordinary scenario – your app can’t just load its bootstrapping configuration while running.

Even more common is the case with html & css changes. You just can’t live without “save & refresh” there. But that works perfectly fine – JSPs are refreshed by the servlet container (unless you are in production mode), and each view technology has an option for picking template files dynamically. And that has nothing to do with the JVM.

So you can develop web applications with Java almost as quickly as with any scripting language.

Finally, I must mention one product with a slogan “Stop redeploying in Java” – JRebel. They have created a very good product that is an improved HotSwap – it can swap structural changes as well. And has support for many frameworks. The feature list looks really good. While it’s a great product, I wouldn’t say it’s a must. You can be pretty productive without it.

But be it HotSwap or JRebel – you must make sure you don’t redeploy to reflect changes. That is a real productivity killer.

Reference: Change Without Redeploying With Eclipse And Tomcat from our JCG partner Bozho at the Bozho’s tech blog.

Related Articles :

Do you want to know how to develop your skillset to become a Java Rockstar?

Subscribe to our newsletter to start Rocking right now!

To get you started we give you our best selling eBooks for FREE!

1. JPA Mini Book

2. JVM Troubleshooting Guide

3. JUnit Tutorial for Unit Testing

4. Java Annotations Tutorial

5. Java Interview Questions

6. Spring Interview Questions

7. Android UI Design

and many more ....


Leave a Reply

Your email address will not be published. Required fields are marked *


Want to take your Java Skills to the next level?
Grab our programming books for FREE!
  • Save time by leveraging our field-tested solutions to common problems.
  • The books cover a wide range of topics, from JPA and JUnit, to JMeter and Android.
  • Each book comes as a standalone guide (with source code provided), so that you use it as reference.
Last Step ...

Where should we send the free eBooks?

Good Work!
To download the books, please verify your email address by following the instructions found on the email we just sent you.