exception_exp.rb

require 'java'

class Error  < Java::JavaLang::RuntimeException; end
class Error1 < Error; end
class Error2 < Error; end
class Error3 < Error; end

def err1
  raise Error1.new("err")
end

def err2
  begin
    err1
  rescue Error1 => e
    raise Error2.new(e)
  end
end

def err3
  begin
    err2
  rescue Error2 => e
    raise Error3.new(e)
  end
end

def err
  begin
    err3
  rescue => e
    raise Error.new(e)
  end
end

begin
  err
rescue => e
  $stderr.puts "e: {class:#{e.class},msg:#{e}}"
  $stderr.puts "e.cause: {class:#{e.cause.class},msg:#{e.cause}}"
  $stderr.puts "e.cause.cause: {class:#{e.cause.cause.class},msg:#{e.cause.cause}}"
  $stderr.puts "e.cause.cause.cause: {class:#{e.cause.cause.cause.class},msg:#{e.cause.cause.cause}}"
end

log

e: {class:Error,msg:org.jruby.proxy.java.lang.RuntimeException$Proxy1: org.jruby.proxy.java.lang.RuntimeException$Proxy1: org.jruby.proxy.java.lang.RuntimeException$Proxy1: err}
e.cause: {class:Error3,msg:org.jruby.proxy.java.lang.RuntimeException$Proxy1: org.jruby.proxy.java.lang.RuntimeException$Proxy1: err}
e.cause.cause: {class:Error2,msg:org.jruby.proxy.java.lang.RuntimeException$Proxy1: err}
e.cause.cause.cause: {class:Error1,msg:err}