Getting JDB to work with my own JPDA connector
Ok, I am now officially confused...
I read http://java.sun.com/j2se/1.5.0/docs/guide/jpda/jpda_spis.html,
and deployed my connector (for now, just to see that it works,
Sun's sample one) as they specified (created a jar with
META-INF/services/com.sun.jdi.connect.Connector file, and
placed it in jre/lib/ext -- I then also tried placing it in other folders,
nothing worked).
I then tried to do connect to it with JPDA (as specified in
http://java.sun.com/j2se/1.5.0/docs/guide/jpda/conninv.html#JDB).
I tried using -connect option, but it said
invalid option: -connect=org.hrum.dbdb.DbdbLaunchingConnector
(and gave me a usage screen which included -connect).
I then tried to just do jdb -listconnectors, and,
I got
java.lang.NoClassDefFoundError: com/sun/jdi/connect/LaunchingConnector (even though I
specified tools.jar in -classpath option)
and then a list of connectors (which didn't include mine).
Now, when I reread "Connecting with JDB" paragraph, the phrase
"The example implementation of JDB provided with the JPDA"
caught my eye. I then thought that I need another JDB, the
reference one that comes with JPDA download, not the one included
with JDK. But then, http://java.sun.com/products/jpda/download.html
claims JPDA is already included with the download. So what's up?
[1441 byte] By [
juntaa] at [2007-10-2 0:52:55]
Im only learning the JPDA myself so im not going to be much help to you other than to suggest you read http://java.sys-con.com/read/36221.htm which has been of some help to myself.
Taking your last question first, for anything newer than 1.2.2, the
most recent jdb is included in your JDK download. The
executable code is baked in (via the jdb launcher and the classes in
tools.jar). If you want to take a look at the source code, that is
also available in $JAVA_HOME/demo/jpda/examples.jar. Unpack
this .jar file to see the sources:
jar -xvf $JAVA_HOME/demo/jpda/examples.jar
In a 5.0/Tiger (or later) environment, a jdb -listconnectors
command should enumerate the connectors available:
Try this:
% jdb -J-showversion -listconnectors
java version "1.5.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0-b64)
Java HotSpot(TM) Client VM (build 1.5.0-b64, mixed mode)
Available connectors are:
Connector: com.sun.jdi.CommandLineLaunch Transport: dt_socket
description: Launches target using Sun Java VM command line and attaches to it
Argument: home Default value: /export/u4/opt/jdk-1_5_0-fcs-b64/jre
description: Home directory of the SDK or runtime environment used to launch the application
Argument: options (no default)
description: Launched VM options
Required Argument: main (no default)
description: Main class and arguments, or if -jar is an option, the main jar file and arguments
Argument: suspend Default value: true
description: All threads will be suspended before execution of main
Required Argument: quote Default value: "
description: Character used to combine space-delimited text into a single command line argument
Required Argument: vmexec Default value: java
description: Name of the Java VM launcher
Connector: com.sun.jdi.RawCommandLineLaunch Transport: dt_socket
description: Launches target using user-specified command line and attaches to it
Required Argument: command (no default)
description: Raw command to start the debugged application VM
...
I added -J-showversion to the jdb command line to make sure I
was running the environment I was expecting.
What is the output of java -version and jdb -J-showversion
-listconnectors in your environment?
Forgive me for starting with these first principles - but anything
else is wasted time unless the basic environment is OK.
Ah, I think the problem is on this page:
thttp://java.sun.com/j2se/1.5.0/docs/guide/jpda/jpda_spis.html
It suggests copying the JAR file to the extensions directory. As the JDI classes are in tools.jar it means they are on the system class path. This is why you get the "java.lang.NoClassDefFoundError: com/sun/jdi/connect/LaunchingConnector" error.
To fix the problem I suggest doing:
1. Remove your JAR file from the extensions directory.
2. Try this:
jdb -classpath <YOUR-JAR-FILE> -listconnectors
If this lists your Connector then you are in business. Then you can use "jdb -connect <connector>...". I see in your post that you have "-connect=<connector>" but that is not the right syntax.
The syntax is "jdb -connect <connector>:<name=value>...." . It looks like you have "jdb -connect=<connector>"
Ok, I've figured out what's going on for now...
1. I had to put tools.jar from the JRE's home (as different from
JAVA_HOME, which, apparently, is assumed to be JRE's home -- to wit,
if you have JDK installed, it's, e.g., D:\jdk1.5.0\jre rather than
D:\jdk1.5.0). In other words, dropping the tools.jar into the jre/lib/ext
folder in addition to it's righteous place in <JDK_INSTALL_DIR>lib did
the trick of getting rid of that pesky ClassDefFoundError. .
2. You should properly override name() of the Connector you're
implementing correctly for diagnostic (so that you're not confused by
the output of jdb -listconnectors) but that's a minor thing...
And to follow up:
1. javakicksass: Nice link, btw...
2. timbell: thanks for the -J-showversion tip
3. alan.bateman: See above (I tried the -classpath thingie, didn't
seem to work...)
juntaa at 2007-7-15 18:12:37 >
The reason it is working for your now is that tools.jar and your Connector are in the extensions directory and hence loaded by the extensions class loader. You don't need to do this. The error in the jpda_spis page is that it suggests copying the Connector to the extensions directory - that is an error. So if you remove these from the extensions directory and just put tools.jar and your Connector on the classpath then it should just work.
Well, actually, no...What do you mean by "on classpath"? the -classpath optionto JDB is not for JDB, it's for whatever JDB is debugging. It hasno effect as far as JDB finding connector. If you mean justputting it in JAVA_HOME/lib, that has no effect either...
juntaa at 2007-7-15 18:12:37 >
jdb is just a native wrapper that executes com.sun.tools.examples.debug.TTY. The native wrapper is compiled with the classpath set to tools.jar (plus sa-jdi.jar Solaris/Linux).
For you to have your Connector visible to jdb then you need to put it on jdb's classpath which you can do with:
jdb -J-classpath -J$JAVA_HOME/lib/tools.jar:MyConnector.jar -listconnectors
(if you are on Windows then it will be something like "jdb -J-classpath -J%JAVA_HOME%\lib\tools.jar;MyConnector.jar -listconnectors")
Alternatively, this should do it too:
java -classpath $JAVA_HOME/lib/tools.jar:MyConnector.jar com.sun.tools.examples.debug.TTY -listconnectors
> 1. javakicksass: Nice link, btw...No problem, glad it was useful, it certainly helped me get started on my project.
