How can I enable logging in NVelocity? - nvelocity

Question

Any idea how to do what the title says? Only thing I found was on the original Velocity site, and I don't think
ve.setProperty( RuntimeConstants.RUNTIME_LOG_LOGSYSTEM_CLASS,
"org.apache.velocity.runtime.log.Log4JLogChute" );
ve.setProperty("runtime.log.logsystem.log4j.logger",
LOGGER_NAME);
will work wonderfully well on .NET. I am using log4net, which should make it quite easy, but the documentation on NVelocity is really a mess.

Answer 1

Implement NVelocity.Runtime.Log.ILogSystem (you could write a simple implementation that bridges to log4net) and set this impl type in the property RuntimeConstants.RUNTIME_LOG_LOGSYSTEM_CLASS
How I got this information:
Get the code.
Search for "log" in the codebase
Discover the classes in NVelocity.Runtime.Log.
Read those classes' source, they're very simple and thoroughly documented.

Answer 2

Update:
Currently, NVelocity does not support logging. The initializeLogger() and Log() methods in RuntimeInstance Class are commented out.
If you need to log, uncomment the two methods, add a private ILogSystem logSystem; property
Here's our on-the-fly implementation:
public class RuntimeInstance : IRuntimeServices
{
private ILogSystem logSystem;
...
...
private void initializeLogger()
{
logSystem = LogManager.CreateLogSystem(this);
}
...
...
private void Log(LogLevel level, Object message)
{
String output = message.ToString();
logSystem.LogVelocityMessage(level, output);
}
...
}
Then, we implemented ILogSystem for log4net
using log4net;
using NVelocity.Runtime;
using NVelocity.Runtime.Log;
namespace Services.Templates
{
public class Log4NetILogSystem : ILogSystem
{
private readonly ILog _log;
public Log4NetILogSystem(ILog log )
{
_log = log;
}
public void Init(IRuntimeServices rs)
{
}
public void LogVelocityMessage(LogLevel level, string message)
{
switch (level)
{
case LogLevel.Debug:
_log.Debug(message);
break;
case LogLevel.Info:
_log.Info(message);
break;
case LogLevel.Warn:
_log.Warn(message);
break;
case LogLevel.Error:
_log.Error(message);
break;
}
}
}
}
Then, when creating the engine:
var engine = new VelocityEngine();
var props = new ExtendedProperties();
props.SetProperty(RuntimeConstants.RUNTIME_LOG_LOGSYSTEM,
new Log4NetILogSystem(LogManager.GetLogger(typeof(NVelocityEngine))));
engine.Init(props);