How to use jdb for debugging a servlet?
I'm using Apache/JServ with jdk 1.4 (via Textpad on win2K SP 3).
The 'gospel' I'm trying to follow is:
'Start the server manually and record the password for remote debugging
(this is displayed on the console).'
'Start the Java debugger:'
'jdb -host your_host -password the_password'
'You should be able to debug your Java classes now using the jdb
command.'
My problem is that I can't find the password from Apache.
I normally start/restart apache as a windows Service.
If I start it from DOS I get:
'C:\orant9i\Apache\Apache>apache -k start'
'Oracle HTTP Server Powered by Apache/1.3.12 (Win32) ApacheJServ/1.1
mod_ssl/2.6.4 OpenSSL/0.9.5a mod_perl/1.24 running...'
I've searched the log, conf & property files but can't find any password.
I've also searched the Apache website for 'jdb' without luck.
I've printed out (and read!) the 'Using Apache with MS Windows' manual.
I did a Google:
--Someone suggested starting Apache using using the -X flag, but I don't
seem to have this option.
--Someone else suggested changing jvm12.conf, but I don't have one.
I have tried the following, just-in-case I don't really need a password,
but it doesn't tell me a lot, and I would appreciate some help:
JDB -sourcepath E:\javaPackages org.apache.jserv.JServServletManager
C:\orant9i\Apache\Apache>JDB org.apache.jserv.JServServletManager
Initializing jdb ...
> run
run org.apache.jserv.JServServletManager
Set uncaught java.lang.Throwable
Set deferred uncaught java.lang.Throwable
>
VM Started:
Exception occurred: java.lang.ClassNotFoundException (uncaught)"thread=main", java.net.URLClassLoader$1.run(), line=199 bci=72
main[1] list
Source file not found: URLClassLoader.java
main[1]
Thanks,
Peter.
Posted to alt.apache.configuration, comp.lang.java, http://groups.yahoo.com/group/win-apache and
comp.infosystems.www.servers.misc with no response
[2127 byte] By [
chattpa] at [2007-9-29 20:10:12]
You can attach to and debug any process running a modern Java[tm] VM
as long as it is started with valid debug flags such as "-Xdebug -Xrunjdwp:...."
By "modern" I mean 1.2.2 or newer (with a few exceptions noted on the
download page):
http://java.sun.com/products/jpda/download.html
You wrote:
>The 'gospel' I'm trying to follow is:
>'Start the server manually and record the password for remote debugging
>(this is displayed on the console).'
'>Start the Java debugger:'
>'jdb -host your_host -password the_password'
'>You should be able to debug your Java classes now using the jdb
>command.'
This recipie is out of date. That is the description for using the old
sun.tools.debug debugger, which pre-dates the JDI interface.
The old jdb was never compatable with any HotSpot VMs, so it
was removed completely in 1.4 or 1.4.1 (Bug-ID 4341203)
http://developer.java.sun.com/developer/bugParade/bugs/4341203.html
The jdb based on the Java Debug Interface (JDI) does not provide or
require a debug password.
You need to get the VM running your Servlet started with the appropriate
debug flags. Then you will be able to attach jdb to it.
I am not familiar with the specifics of the Apache/JServ configuration,
but there must be a place or config file where you specify the JVM
you want and the run flags you want to use. You need to add flags
like this:
-Xdebug -Xrunjdwp:transport=dt_socket,address=8000,suspend=n,server=y
(Make sure the socket address you select (8000 in this example) is not in use.)
Then, after apache has started and you see the JVM running in your process
display, you will be able to attach jdb to the socket address specified above:
jdb -connect com.sun.jdi.SocketAttach:hostname=localhost,port=8000
For more information, refer to "Connection and Invocation Details":
http://java.sun.com/j2se/1.4.2/docs/guide/jpda/conninv.html
Thanks for your help.
I added the following to jserv.properties:
wrapper.bin.parameters=-Xdebug
wrapper.bin.parameters=-Xrunjdwp:transport=dt_socket,address=2930,suspend=n,server=y
and it ran the servlet okay.
But I get the following when I try to start jdb:
jdb -connect com.sun.jdi.SocketAttach:hostname=localhost,port=2930 org.apache.jserv.JServServletManager
gives:
Cannot specify command line with connector:
com.sun.jdi.SocketAttach:hostname=localhost,port=2930,
and
jdb -attach localhost:2930 org.apache.jserv.JServServletManager
gives:
Cannot specify command line with connector: com.sun.jdi.SharedMemoryAttach:name=localhost:2930,
I'm going to keep working on it but thought I'd upload this as it's late and I'm not too optimistic.
BTW, am I using the right class?
Thanks again,
Peter.
[/code]
UPDATE
Well, I got lucky.
After re-reading the Connection and Invocation Details paper you recommended, (and remembering i'm using windows), I tried:
C:\orant9i\Apache\Apache>jdb -connect "com.sun.jdi.CommandLineLaunch:main=org.apache.jserv.JServServletManager
Initializing jdb ...
> run
run org.apache.jserv.JServServletManager
Set uncaught java.lang.Throwable
Set deferred uncaught java.lang.Throwable
>
VM Started:
Exception occurred: java.lang.ClassNotFoundException (uncaught)"thread=main", java.net.URLClassLoader$1.run(), line=199 bci=72
main[1]
This is obviously the right way to make contact, but with what?
It looks like I need a class with a 'main' to connect to, and that sure isn't my servlet, and doesn't seem to be JServServletManager.
Any ideas?
Thanks,
Peter.
[/code]
Hello
You wrote:
> I added the following to jserv.properties:
>wrapper.bin.parameters=-Xdebug
>wrapper.bin.parameters=-Xrunjdwp:transport=dt_socket,address=2930,suspend=n,server=y
> and it ran the servlet okay.
Fine so far. This means your debugee VM is started and running. The "suspend=n" means it
will start running without waiting for a debugger to attach... so you can attach later whenever you
decide to debug. Note that 'later' could be weeks later, or possibly never.
Now: Time to attach jdb to the victim/debugee process you started above.
You wrote:
> But I get the following when I try to start jdb:
>jdb -connect com.sun.jdi.SocketAttach:hostname=localhost,port=2930 org.apache.jserv.JServServletManager
> gives:
>Cannot specify command line with connector:
>com.sun.jdi.SocketAttach:hostname=localhost,port=2930,
>and
>jdb -attach localhost:2930 org.apache.jserv.JServServletManager
>gives:
>Cannot specify command line with connector: com.sun.jdi.SharedMemoryAttach:name=localhost:2930,
The problem here is that you are trying to supply too much information to jdb.
When you are using the attach connectors, all you need to supply is the
host name and socket (for the socket connectors), or the name of the shared memory
area (for the shared memory connector). The connectors you tried above are throwing
an error because you are trying to supply something extra (the class name).
When doing an attach, the debugee VM is already launched. The debugger will
attach to it and inspect the classes loaded.
If you are still running with the wrapper.bin.parameters you listed above,
then all you need to connect with jdb is:
jdb -connect com.sun.jdi.SocketAttach:hostname=localhost,port=2930
You should get a jdb prompt, and you will be able to inspect the debugee
VM by entering commands such as threads and classes. Typically
the next thing would be to set some breakpoints (stop in package.class.method,
or stop at package.class:line. Then restart the debugee with a resume.
