Re: Strange crashes in JDBC code in multithreaded application.

On Sun, 5 Aug 2007, L. Rahyen wrote:

> Exception in thread "Thread-108" java.lang.NullPointerException
> at
> org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:182)
> at ...
> at java.lang.Thread.run(libgcj.so.70)
>

This area of code reads:

175 if (parameters == null)
176 parameters = SimpleQuery.NO_PARAMETERS;
177
178 boolean describeOnly = (QUERY_DESCRIBE_ONLY & flags) != 0;
179
180 // Check parameters are all set..
181 if (!describeOnly)
182 ((V3ParameterList)parameters).checkAllParametersSet();

So it's complaining that parameters is null, but the code on line 175
should take care of that case. I note that you're using GCJ, does this
problem occur when using a Sun JVM?

> 1) This is a bug in JDBC. Is JDBC thread-safe? Is it supposed to be
> thread-safe by design? Obviously if not then initializing conn
> every time will be inefficient and I need to write a separate server to
> execute PSQL queries because I want to connect only once to the DB.

JDBC is thread safe. While PG's driver can only execute one query at a
time, it should block, not die like this.

Kris Jurka