How does one tell JRuby to reload/refresh a Java Class?

开发者_开发技巧

I am scripting Java using JRuby. By using JRebel, I can the automatically reload changed Java classes into the JRuby JVM without restarting. When I add a new Java method JRebel automatically reloads the class. My problem is that I cannot call this new method directly. Can I ask JRuby to refresh its method cache for the newly reloaded Java class? My only workaround is to call the new method reflectively using java_send.

Example:

step 1. Start irb session and java_import a Java class (say Person).

step 2. Add a getName method to Person and compile.

step 3. Create an instance of Person (p = Person.new). JRebel will show that it reloaded the java class.

step 4. Calling p.get_name results in a NoMethodError but p.java_send('getName') invokes the newly implemented getName method

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I found a way to run JRuby with JRebel!

The trick is to start JRuby with Nailgun server which is using the JRebel like this:

jruby --ng-server -J-javaagent:/Applications/ZeroTurnaround/JRebel/jrebel.jar -J-noverify

Now rails application can be started with Nailgun:

jruby --ng -S rails server

If rails uses Java classes from somewhere and it can find proper rebel.xml, the JRebel will pickup the changes and you don't need to restart the rails anymore.

$CLASSPATH << "#{RAILS_ROOT}/java/target/classes"

JRuby/JRebel still needs more work as the JRuby is not picking up the changes to the class declarations, only the contents of the known methods.

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Did you manage to pass the -javaagent option so that it gets recognized by JIRB and start jrebel agent?

jruby -J-noverify -J-javaagent:/path/to/jrebel.jar -S jirb

I've tried this, but don't see it working, also with java_send