OK, I'm having a bit of a quandary, which is probably obviously simple to
everyone else.
I start up an H2 server from the command line, thus: java -cp h2-latest.jar
org.h2.tools.Server -tcp -tcpPort 9091 -tcpAllowOthers
In my application (currently being debugged in Eclipse, but it shouldn't
matter), I connect to the server thus:
URL="jdbc:h2:tcp://192.168.0.102:9091/file://C:\Development\VARisk Related
Files\workspace\TC_VARisk\VARiskDB"; (It's not actually hard-coded in the
app, this is a sample of a generated URL to make it clear.)
Connection conn=conn = DriverManager.getConnection(URL, "sa", "");
This has been working fine for a long time now.
I created a very basic stub class that implemented DatabaseEventListener,
with a few printlns to show that it was working, etc.
The first thing I tried was changing my code for the URL to include
";DATABASE_EVENT_LISTENER='"+H2DBListener.class.getName()+"'"
This threw "class not found" exceptions. I tried a lot of variants on this
theme before the caffeine hit and I figured it out. Once I was done bashing
my head on the desk, I built a .jar containing my H2DBListener class, and
added it to the classpath for the H2Server startup.
This stopped the "class not found" errors. Unfortunately, the Listener is
outputting information to the server console, not the Eclipse console. I
need it tied to the connection I create internally to my app.
Further, I really need to be able to create an object of the H2DBListener
class, attach it during particular processes I care about listening to, and
then detach it. Is there a way to do something like:
H2DBListener h=new H2DBListener();
SetDatabaseEventListener(h);
I noticed that there is a SQL command to set the DBEvent listener, but it
also sets it to a class, not an instance.
To be clear as to my long term goals, what I mostly want/need is to be able
to do something like this:
class someLongProcess implements DatabaseEventListener
{
ProgressBar pb=new ProgressBar();
...
public void DoSomething()
{
//here's where I'd like to attach the listener
query="Select * from HugeDatabase";
executeQuery();
//here's where I detach the listener
}
public void setProgress(int state, String name, int x, int max)
{
if(state==valueICareAbout)
{
pb.update(x,max);
}
}
}
To make matters more interesting, my app runs (when doing real work) in
multiple VMs. It's a very simple work splitting model, using Cajo to
coordinate the small amount of state I need to share -- and of course part
of that state is "how far long are we?". Currently, I probably don't need
to use DatabaseEventListener, because progress on the main function of the
application is already being tracked and shared, but I see a future time
when I might need to implement it, so I wanted to bring it up. What happens
if/when multiple connections to the same server set or unset the Listener
class? If it's tied to the connection, that's likely no issue; each class
that creates a connection and needs a listener ought to be fairly atomic in
what it's doing and what it's listening for. I want to be sure that if
class foo calls SET DATABASE_EVENT_LISTENER, it won't be affected by what
class bar, running in a different thread in the same VM, or in another VM
entirely, does.
Thank you for your patience with what are probably self-evident questions.
Also, I normally only edit in plain text in gmail, but to make the code
more readable, I had to switch to rich formatting. I hope it actually is
formatted clearly on other people's systems.
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