How to use DCEVM/Hotswap Agent with jar file update?

Question

I am running a java spring boot application as jar file with DCEVM hot-swap agent. When i change some class files in my jar file the application is not reloading those changes. But If I extract my jar file and run my application as a simple java class file adding all dependencies to class path( like how IntelliJ Idea does) then replace any of the class file it reloads successfully.

Running extracted jar file:

java -XXaltjvm=dcevm -javaagent:path/hot-swap/hotswap-agent-1.3.1-SNAPSHOT.jar=autoHotswap=true -Dspring.profiles.active=local -Dserver.port=8082 -classpath path/jdk1.8.0_191.jdk/Contents/Home/jre/lib/charsets.jar:--jdk-lib-jars:./path/classes:..other-jar-file-path com.company.app.App

after running above command if I am making any changes and recompiling and then replacing updated class file then the changes are detected and my app reflects the changes.

HOTSWAP AGENT: 15:35:55.349 RELOAD (org.hotswap.agent.config.PluginManager) - Reloading classes [com.company.controller.HealthController] (autoHotswap)

I get above log which tells me that class is reloaded. everything works fine.

Running jar file:

java -XXaltjvm=dcevm -javaagent:path/hot-swap/hotswap-agent-1.3.1-SNAPSHOT.jar=autoHotswap=true -Dspring.profiles.active=local -Dserver.port=8081 -jar app.jar

After running If I update the jar file with following command:

jar uf app.jar path/HealthController.class

jar file gets updated but changes does not reflect and there is no log generated.

Answer 1

HotswapAgent does not detect class modification inside jar file. Instead of it you can use extraClasspath config param. Look at http://hotswapagent.org/mydoc_configuration.html how to setup it.