Chapter 12 Creating CORBA-Java Components

Debug Java components

You can debug Java components that are executing in the Jaguar server.

Before you start

Debugging Java components requires the following:

Java debugging must be enabled for your Jaguar server. Display the properties window for the server (right-click and select Server Properties from the pop-up window), display the Debug tab, and select the Enable Java Debugging option. The change takes effect the next time you start the debug version of the Jaguar server.
The debug version of the Jaguar server must be running. On NT, use either of the following to start a debuggable server:
- Launch the Jaguar Server (dev) icon
- Run the script %JAGUAR%/bin/serverstart_dev.bat.
On UNIX, run the script $JAGUAR/devbin/srvstart_dev.
You need a JDK-1.1-compatible Java debugger that supports remote debugging, such as PowerJ or the JDK 1.1 jdb tool.
Component class files must include symbol information for fields and local variables. If you are compiling with javac, components must be compiled with the -g option. If you use a Java IDE, set the equivalent option to build debuggable class files.
Source files must be available to the debugger. The required location for source files depends on your debugging tool:
- For jdb, source files must be on the Jaguar server host, in the directory from which the corresponding class file is loaded.
- PowerJ uses local source files from the project directory.
- For other IDE debuggers, consult the IDE documentation for source file requirements when you are debugging remotely.

Steps to debug an executing component

Follow the steps below to debug Java components.

The included examples use jdb and the Sybase Virtual University Enrollment_Java component.

Make sure that you have enabled Java debugging in the Jaguar server and that you are running the debug version of the server (see "Before you start"). Make sure no one else is debugging components using the same server (the server-side debugger supports only one remote-debugger connection at a time).
Find the remote-debugger password in the server's console window. For example, the password is k53js in the output reproduced below:
```
Agent Password=k53js
```
You will need this password to connect to Jaguar with your debugger.
Start your debugger and connect to Jaguar. For example, with jdb:
```
jdb -host localhost -password k53js
```
Once connected, you can specify breakpoints for the debugger to stop at in your component implementation. Set the breakpoint before running any client applications that will exercise the target line of code. For example (the following must be entered on one line):
```
stop at Sample.SVU.javaComp.
Enrollment_Java.Enrollment_JavaImpl:74
```
(This breakpoint corresponds to the CreateStudentRecord method in the Enrollment_Java component.)
Run a client application that will invoke the target component code. For example, to debug the CreateStudentRecord method in the Java_Enrollment component, run the SVU Java example client in your Web browser and create a new student record on the login screen. In the debugger, you should see some indication that the breakpoint has been reached.

You may need to change the debugger's active thread before the component breakpoint is indicated. Jaguar runs each Java component instance in a separate Java thread. The component thread must be the active debugger thread in order to step through the component's code. In jdb, use the threads command to list the executing threads. You can then use the thread command to switch to the thread that is running the component.

Once the breakpoint is tripped, you can step through the code, inspect fields and variables, and so forth. For example, in jdb:

Thread-21[1] where 6

  [1] Sample.SVU.javaComp.Enrollment_Java.Enrollment_JavaImpl.
createStudentRecord (Enrollment_JavaImpl:74)

Thread-21[1] print student_id

student_id = 333-33-3333

Thread-21[1] cont

Debugging class loading and unloading problems

Jaguar Manager provides the following server properties to log information about Java class loading and unloading.You can set these properties on the All Properties tab in the Server Properties dialog box:

Property	Description
com.sybase.jaguar.server.jvm.verbose	When this property is set to `true` , the server logs all Java classes that are loaded and the location where each class file was read.
com.sybase.jaguar.server.jvm.verboseGC	When this property is set to `true` , the Jaguar server logs information when memory is freed by the Java garbage collector.

The default for both properties is false .