Using hotswapAgent with Tomcat

[Mark Gordon]

I am using Tomcat 8 with jdk 1.8.0_112.

I am using the latest hotswapAgent.  Patched my JDK.

I see the hotswap messages in the log files.

I make a small change to a class.  Recompile but don't see the change when I use the class from a JSP page.  Real simple test case.

I am a user of JRebel and I am using hotswap agent as I did in jrebel with the same setup.  Am I missing something? 

Thanks

Mark

HOTSWAP AGENT: 13:38:16.862 INFO (org.hotswap.agent.config.PluginRegistry) - Plugin 'org.hotswap.agent.plugin.tomcat.TomcatPlugin' initialized in ClassLoader 'ParallelWebappClassLoader

  context: solr

  delegate: false

----------> Parent Classloader:

java.net.URLClassLoader@1f28c152

'.

HOTSWAP AGENT: 13:38:16.862 INFO (org.hotswap.agent.plugin.tomcat.TomcatPlugin) - Tomcat plugin initialized - Tomcat version '8.5.9.0'

[vladimir dvorak]

Check if our class was depoyed to Tomcat, then look at messages related to JSP here and issues on HA's github repo.

[Mark Gordon]

The class file was deployed to my webapp's WEB-INF/classes folder  It does not seem to see the change and is not reloading.

Does this not work with JSP pages?  Tomcat is attempting to recompile the jsp and it is not seeing the new method added to the class.

I must have something not set up correctly.  This is about as simple of a test as you could have with tomcat.

I read something about debug mode?  Is the reload service turned off by default.  Do I need to somehow turn it on?

Thanks,

-Mark

[vladimir dvorak]

If the class is not redefined in JVM then you are either not using debugger or you missed configure Auto Hotswap. We have solved a similar problem with JSP recently. I would recommend you to look at the sample project from this issue.

[Mark Gordon]

So you have to start tomcat with debug?  I have never done this.  So yeah I am not using the debugger.

When I try to start tomcat with debug I get this error (catalina.sh debug) :

invalid option: -javaagent:/u/mark/Downloads/hotswap-agent-1.1.0-SNAPSHOT.jar

That option works when using catalina.sh run

[vladimir dvorak]

-javaagent:/u/mark/Downloads/hotswap-agent-1.1.0-SNAPSHOT.jar  is JVM option. But you can use HA without debugger using autoHotswap=true - look at the project I've sent.

[Mark Gordon]

Thanks Vladimir,

I am making some progress!!!  I added autoHotSwap=true.

I made a small change to a method.  I changed the output in a System.out.println statement.

Now if I change a class and recompile the class I get this:

HOTSWAP AGENT: 14:31:31.969 RELOAD (org.hotswap.agent.config.PluginManager) - Reloading classes [com.sunbeltdcs.rules.ItemValue] (autoHotswap)

Exception in thread "Thread-1309" java.lang.IllegalStateException: Unable to redefine classes

at org.hotswap.agent.config.PluginManager.hotswap(PluginManager.java:272)

at org.hotswap.agent.plugin.hotswapper.HotswapperPlugin$1.executeCommand(HotswapperPlugin.java:94)

at org.hotswap.agent.command.impl.CommandExecutor.run(CommandExecutor.java:25)

Caused by: java.lang.UnsupportedOperationException: class redefinition failed: attempted to add a method

at sun.instrument.InstrumentationImpl.redefineClasses0(Native Method)

at sun.instrument.InstrumentationImpl.redefineClasses(InstrumentationImpl.java:170)

at org.hotswap.agent.config.PluginManager.hotswap(PluginManager.java:269)

[Mark Gordon]

I was able to get it to load a change to an existing method in a class.  It had to be a really simple class.  I had a class that extended another class and it could not reload that class, not sure if that was why.  It was a bigger class.

The real simple case of having a base class with one method.  I made a small change and it reloaded the change.  I added a new method and got the same error that adding a new method was unsupported.

Exception in thread "Thread-1365" java.lang.IllegalStateException: Unable to redefine classes

at org.hotswap.agent.config.PluginManager.hotswap(PluginManager.java:272)

at org.hotswap.agent.plugin.hotswapper.HotswapperPlugin$1.executeCommand(HotswapperPlugin.java:94)

at org.hotswap.agent.command.impl.CommandExecutor.run(CommandExecutor.java:25)

Caused by: java.lang.UnsupportedOperationException: class redefinition failed: attempted to add a method

at sun.instrument.InstrumentationImpl.redefineClasses0(Native Method)

Exception in thread "Thread-1364" at sun.instrument.InstrumentationImpl.redefineClasses(InstrumentationImpl.java:170)

at org.hotswap.agent.config.PluginManager.hotswap(PluginManager.java:269)

... 2 more

Exception in thread "Thread-1363" java.lang.IllegalStateException: Unable to redefine classes

at org.hotswap.agent.config.PluginManager.hotswap(PluginManager.java:272)

at org.hotswap.agent.plugin.hotswapper.HotswapperPlugin$1.executeCommand(HotswapperPlugin.java:94)

at org.hotswap.agent.command.impl.CommandExecutor.run(CommandExecutor.java:25)

Caused by: java.lang.UnsupportedOperationException: class redefinition failed: attempted to add a method

at sun.instrument.InstrumentationImpl.redefineClasses0(Native Method)

at sun.instrument.InstrumentationImpl.redefineClasses(InstrumentationImpl.java:170)

at org.hotswap.agent.config.PluginManager.hotswap(PluginManager.java:269)

... 2 more

java.lang.IllegalStateException: Unable to redefine classes

at org.hotswap.agent.config.PluginManager.hotswap(PluginManager.java:272)

at org.hotswap.agent.plugin.hotswapper.HotswapperPlugin$1.executeCommand(HotswapperPlugin.java:94)

at org.hotswap.agent.command.impl.CommandExecutor.run(CommandExecutor.java:25)

Caused by: java.lang.UnsupportedOperationException: class redefinition failed: attempted to add a method

at sun.instrument.InstrumentationImpl.redefineClasses0(Native Method)

at sun.instrument.InstrumentationImpl.redefineClasses(InstrumentationImpl.java:170)

at org.hotswap.agent.config.PluginManager.hotswap(PluginManager.java:269)

... 2 more

[Jiří Bubník]

Hi,

 

Caused by: java.lang.UnsupportedOperationException: class redefinition failed: attempted to add a method

 

You did not use DCEVM JVM (either patched java, or –altjvm switch).

 

Jiri

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