How can I use "for ,while and if " in the script file?

[89332874]

Dear all,

I want to inject some "for,while and if" instructions into myapp  . Could anyone tell  me how I can do it ?

Thank all!

[adinn]

Hi Wang Shuai,

I want to inject some "for,while and if" instructions into myapp  . Could anyone tell  me how I can do it ?

You cannot use for, while and if in the IF or DO clauses of a Byteman rule. This is a deliberate choice. If you want to use complex control flow then you need to implement a helper class and call a method of the helper class from your rule. For example, here is a rule which uses a helper class to print all elements of a list

RULE dump list data
CLASS org.my.app.MyClass
METHODmyMethod(List)
HELPER org.my.helper.MyHelper
AT ENTRY
IF TRUE
DO dumpList($1)
ENDRULE

The helper class extends the default helper provided by Byteman and provides one extra public method which can be called from the rule. Notice that the new method uses the existing builtin methods trace() and traceln().

package org.my.helper;
import org.jboss.byteman.rule.helper.Helper;

class MyHelper extends Helper
{
  public void dumpList(List<?> list)
  {
    String prefix = "{";
    for (int i = 0; i < list.size(); i++) {
      trace(prefix);
      trace(list.get(i).toString());
      prefix = ", "
    }
   traceln("}";
  }
}

[89332874]

Thanks! I will create the helper class.  Meanwhile could you public some material about the fundamental and architecture of ByteMan. Thanks again!

[adinn]

Hi Wang Shuai89332874

Meanwhile could you public some material about the fundamental and architecture of ByteMan

The User's Guide explains all that there is to know about using Byteman.

There is not a lot of material about how Byteman is architected/designed.

I suggest you look at the FOSDEM 2012 tutorial (video and slides are available on the Byteman documentation page) which explains a little bit about the JVMTI Java Agent API that Byteman relies on and how Byteman uses that API to change method code at runtime. The JavaSE documentation provides full details of this API (in particular look under Instrumentation at package java.lang.instrument).

The AOSD paper (also on the documentation page) also provides some details of Byteman's architecture.

After that you probably need to study the source code :-)

[89332874]

Got it! Thanks very much!