如何在枚举单例中实现日志记录？

Question

I'm using an enum singleton, but implementing logging is troublesome. This:

public enum Foo {
  INSTANCE;

  private final Logger log = Logger.getLogger(Foo.class.getName());

  ...
}

The logger is instantiated in the way that I would instantiate a logger for a normal Java class, but of course I get the following error:

Foo.java: illegal reference to static field from initializer 

Is there an equivalent way to log in enum singletons?

Answer 1

In answer to your question, just make the logger static...

BTW, I think its standard practice to use a static logger even for object instances. In other words, the logger is on the class; all objects use the static logger references.

See

http://logging.apache.org/log4j/1.2/manual.html

Most of the examples of using a logger in there have the logger as a static property...

Answer 2

动态记录：

Logger.getLogger(Foo.class.getName()).info("log info");

Answer 3

A bit shorter: use a method: logger().debug(...)

private static Logger logger()
{
    if(logger == null)
    {
        logger = Logger.getLogger(AnEnum.class);
    }

    return logger;
}

/** Logger **/
private static Logger logger;