Configure Eclipse for remote debugging an applet. The applet will be running on an internet browser. When a breakpoint is reached, Eclipse should suspend allowing the code to be debugged.
Monday, December 02, 2013
My Tech Experiences: Remote debugging Applet with Eclipse
My Tech Experiences: Remote debugging Applet with Eclipse:
Assignment:
Configure Eclipse for remote debugging an applet. The applet will be running on an internet browser. When a breakpoint is reached, Eclipse should suspend allowing the code to be debugged.
Configure Eclipse for remote debugging an applet. The applet will be running on an internet browser. When a breakpoint is reached, Eclipse should suspend allowing the code to be debugged.
Solutions:
Java provides a protocol to achieve this. You can look
for JDWP in Java documentation for more information. This protocol allows debugging
even a simple class. It works with a server-client mechanism. Either eclipse or
the browser can be set as server.
Steps:
1.
First,
I need to configure the server. I will use eclipse as server, and the applet
will be the client.
From the eclipse menu
choose the option: Remote Java Application.
I used the following
values:
Connection Type: Socket Listen
Port: 9100 - You can use
any value, just make sure the port is not busy.
Go to: Control Panel -> Java -> (Go to Java Tab) ->
Java Runtime Environment.
And add the following line to the Runtime Parameters:
-agentlib:jdwp=transport=dt_socket,server=n,suspend=y,address=9100
The port must match the one you configured in eclipse and the option server must be set to 'n'. You also need to make sure to add the parameters to the correct JRE.
* Like I said, you can debug even a single class. To debug a
standalone class or jar use the line like this:
java –jar -agentlib:jdwp=transport=dt_socket,server=n,suspend=y,address=9100
<class or jar>
3. Add some breakpoint to your code. Run the applet from your browser and the breakpoint should be hit.
Tips:
This is a very simple task. However, it does not always
work as expected (what software does?) I hope this tips can help you to save
some time.
1.
If it does not work try again with a different
version of Java. The newest versions seem to have some security features that
block the remote debugging. I was able to make it work with JRE. 1.7.0_17.
2.
Verify that your JRE is receiving the values. You
can see them in the console.
4.
Signing
the JAR does not seem to be necessary.
5.
You can specify the JRE to use in the applet tag to
be sure that you are using the correct JRE. Add the following line to your
applet tag.
<param
name="java_version" value="1.7.0_17"/>
6. The jar does not need
to be deployed on a server in order to debug it. For this test I created an applet and put it in a jar. Then I created a simple html file with the applet tag. I open my html in a browser, and it worked fine.
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