what's the purpose to generate HikariProxyConnection by javaassist since you already write ProxyConnection ?

[dumbdonkey]

according to the source code, I found ProxyConnection already do a lot of things, HikariProxyConnection only add a try catch block to every method.
I was so confused. it would be nice if anyone can give an explanation. thanks in advance!

[brettwooldridge]

The proxies delegate to the real driver classes. Some proxies, like the one for ResultSet, only intercept a few methods. Without the code generation, the proxy would have to implement all 50+ methods which simply delegate to the wrapped instance.

Code generation, based on reflection, also means that nothing needs to be done when a new JDK version introduces new JDBC methods to existing interfaces.

[dumbdonkey]

@brettwooldridge thanks a lot

[fengchangsheng]

Although the ProxyConnection is a abstract class, as a connection-pooling, must impl this method in fact. Generate these class just for compatible with high version JDK?

[brettwooldridge]

A concrete class is generated from the abstract ProxyConnection class. Any methods that are not "overridden" by the abstract class, and that throw SQLException have delegates generated with the following code:

{
  try {
    return delegate.method($$);
  } catch (SQLException e) {
    throw checkException(e);
  }
}

... which allows us to inspect the exception to see if it represents a disconnection error.

A side-effect is that, yes, the code ends of being flexible with respect to JDBC API changes -- at least all that we have encountered so far.

[fengchangsheng]

@brettwooldridge thanks for the "official" response!