CODEWITHSUNDEEP
javadebuggingbtrace
Jayan
Jayan

Reputation: 18468

JVM process - print every method argument

We use InstallAnywhere to create installers. Recently an installer created using it started failing with StackOverFlow error (in silent installation).. Error stack has thousands of lines like below.

java.lang.StackOverflowError
at com.zerog.ia.installer.util.VariableManager.substitute(Unknown Source)
at com.zerog.ia.installer.util.VariableFacade.substitute(Unknown Source)
at com.zerog.ia.installer.util.VariableFacade.substitute(Unknown Source)
at com.zerog.ia.installer.util.magicfolders.MagicFolder.getPath(Unknown Source)
at com.zerog.ia.installer.util.magicfolders.MagicFolder.toString(Unknown Source)
at com.zerog.ia.installer.util.VariableManager.getValueOfVariable(Unknown Source)
at com.zerog.ia.installer.util.IAVariableStringResolver.getValueOfVariable(Unknown Source)
at com.zerog.ia.installer.util.VariableManager.substitute(Unknown Source)

VariableManager.substitute is very common API, it takes a string argument and return substituted(evaluted) value. How can I see the argument passed to it in the real JVM process?

Upvotes: 1

Views: 749

Answers (1)

Jayan
Jayan

Reputation: 18468

The solution was to use a btrace script.

The installer process is Java process that can be queried by JVM tools like (jps, jstack)

  1. Install JDK (JVisualVM comes with it)
  2. Start VisualVM and Install btrace plugin

enter image description here

  1. Right click on process (LAX) Start 'btrace'

enter image description here

Copy following btrace script to btrace console

package com.sun.btrace.samples;

import com.sun.btrace.BTraceUtils;
import com.sun.btrace.Profiler;
import com.sun.btrace.annotations.*;
import com.sun.btrace.*;

@BTrace class Profiling {
@Property
Profiler swingProfiler = BTraceUtils.Profiling.newProfiler();

@OnMethod(
    clazz="com.zerog.ia.installer.util.VariableFacade", 
    method="/.*substitute.*/")
    void entry( String probeMethod) {
        BTraceUtils.print("Entry" );
        BTraceUtils.println(BTraceUtils.timestamp() );
        BTraceUtils.println(probeMethod);
    }

@OnMethod(
    clazz="com.zerog.ia.installer.*", 
    method="/.*/")
    void entry2( @ProbeMethodName(fqn=true) String probeMethod ) {
        BTraceUtils.print("Entry" );
        BTraceUtils.println(BTraceUtils.timestamp() );
        BTraceUtils.println(probeMethod);
    }

@OnMethod(clazz = "com.zerog.ia.installer.*", method = "/.*/", location = @Location(Kind.RETURN))
     void onPrepareReturn(AnyType arg) {
        if (arg != null) {
             BTraceUtils.println(arg);
        }
    }

}

Start btrace by clicking "start" icon. enter image description here

Watch output for logs.

Btrace is extremely powerful tool to quickly check inside the JVM. Checkout more at Btrace Kenai project

Edit-comment from @J.B Btrace is now at github

Upvotes: 2

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