3 Debugging With NetBeans

3.1 Introduction

You can remotely debug a CDC application with most debuggers that support the Java Virtual Machine Tool Interface (JVMTI) described in http://download.oracle.com/javase/6/docs/platform/jvmti/jvmti.html. The most likely choices are the NetBeans, Oracle JDeveloper, and Eclipse integrated development environments, but you can also use the Java SE jdb command line debugger or another compatible debugger. You run the debugger on a development host, and the application plus CDC on the target device. CDC and the debugger communicate over a network.

CDC debugging has the following limitations:

• Only interpreted code can be debugged.

• CDC-debugger connections must use sockets. Shared memory connections are not supported.

3.2 Launching cvm in Debug Mode

Regardless of the debugger you choose, you launch cvm running the application in the same way.

CVM_HOME=/mnt/sda1/work/cvmCLASSPATH=/mnt/sda1/workCLASSNAME=helloworld.Helloworld

% cvm -agentlib:jdwp=transport=dt_socket,server=y,address=port -Xdebug \
-classpath $CLASSPATH $CLASSNAME

% cvm -agentlib:jdwp=transport=dt_socket,server=n,address=host:port -Xdebug \ -classpath $CLASSPATH $CLASSNAME

% cvm -agentlib:jdwp=transport=dt_socket,server=y,address=8000 -Xdebug -classpath /home/mydir/myclasses.zip HelloWorld
Listening for transport dt_socket at address: 8000

3.3 Attaching the NetBeans IDE Debugger to cvm

Although this section describes the NetBeans debugger, other IDE debuggers that are compatible with the Java Virtual Machine Tool Interface (JVMTI) can be used similarly. This section first describes the most common arrangement in which cvm acts as a server for the debugger, then the converse case.

1. Load the NetBeans project you want to debug and create a debugger operation, such as a breakpoint. Figure 3-1 shows an example.

   Ensure that the project's compiled class files are accessible to the target host and that the class files correspond to the source files loaded in the IDE.

   Figure 3-1 Breakpoint in HelloWorld.java

   
   Description of "Figure 3-1 Breakpoint in HelloWorld.java "
   
   

2. On the target host, launch cvm with server=y and, for this example, address=8000, similar to the example in Section 3.2.2, "cvm Debug Mode Example".

3. In NetBeans, choose Debug > Attach Debugger.

4. Set up the Attach Debugger dialog as shown in Figure 3-2.

   Substitute the target host name for (Target Host).

Figure 3-2 Attach Debugger Dialog (Debugger as Client)

Description of "Figure 3-2 Attach Debugger Dialog (Debugger as Client)"

The debugger connects and indicates that execution has stopped at the breakpoint as similar to Figure 3-3.

Figure 3-3 Debugger Connected and Stopped at Breakpoint

Description of "Figure 3-3 Debugger Connected and Stopped at Breakpoint"

If you want the debugger to be the server, complete the Attach Debugger dialog similar to Figure 3-4. After clicking OK, launch cvm on the target host with server=n and address= the debuggers' host and port.

Figure 3-4 Debugger as Server Attach Debugger Setup

Description of "Figure 3-4 Debugger as Server Attach Debugger Setup "

3.4 Attaching to cvm with jdb

After launching cvm as a debug server (see Section 3.2.2, "cvm Debug Mode Example") on the target host, you can connect to it with the jdb command line debugger using syntax similar to Example 3-4. The jdb command is in JavaSEinstall/bin/.

% jdb -connect com.sun.jdi.SocketAttach:hostname=hostname,port=8000
Set uncaught java.lang.Throwable
Set deferred uncaught java.lang.Throwable
Initializing jdb ...
> 
VM Started: No frames on the current call stack
main[1]