问题
It seems that log4j has some class loading issues (among others) and it seems to me the trend is to move out of log4j toward slf4j. (Hibernate stopped using the first in favor of the latter)
- Is it true?
- What are the main issues in log4j that slf4j solves?
- Is slf4j the final word or is there even a better "the next next log4j" industry standard?
Update:
- So this answer by delfuego confuses me, can you accept / object it?:
You appear to have stumbled upon the major problem with log4j (and the Apache Commons Logging library), namely that they have a ridiculously hard time discovering and interacting with the right classloaders as they're being used. There's a very dense explanation, complete with examples, here; the take-home message is that one of the primary driving forces for the new logging framework SLF4J was to eliminate these issues entirely. You might want to swap it in and see if your life is made any easier.
- More classloading issues by log4j: http://articles.qos.ch/classloader.html
回答1:
Slf4j is indeed just a logging facade. However, Log4j is intended to be succeeded by Logback, from the very same authors.
Update: if you'd like to know about another benefit of Slf4j, it's the fact that following (ugly) constructs aren't needed anymore to avoid the toString() unnecessarily been called:
if (logger.isDebugEnabled()) {
logger.debug("Message: " + bigObject + ", " + anotherBigObject);
}
You can instead make use of parameterized messages:
logger.debug("Message: {}, {}", bigObject, anotherBigObject);
Also see What is the fastest way of (not) logging?
回答2:
Slf4J is not an alternative for Log4j, but rather provides a Façade for logging, so one can you can plug in your own logging framework. It's mainly useful for libraries. from slf4j.org:
The Simple Logging Facade for Java or (SLF4J) serves as a simple facade or abstraction for various logging frameworks, e.g. java.util.logging, log4j and logback, allowing the end user to plug in the desired logging framework at deployment time.
To answer your question: Slf4j is being adopted by frameworks now, but in your projects, you can keep on using Log4J (or any other)
回答3:
First: an important point: Slf4j is the frontend logging (the API), which can use below most of the main loggin systems: log4j or java.util.logging for instance. So it is better to compared sfl4j to commons-logging.
About the state of Log4j, quotes from The state of java logging (one year ago)
One thing that I hadn't realized is that log4j development is essentially dead. It's currently at version 1.2, and plans for version 1.3 were abandoned in favour of developing log4j 2.0. However, it doesn't appear that 2.0 is in active development. It is worth noting that Ceki Gülcü, the original founder of the log4j project, has moved on to slf4j (see below).
回答4:
Looking at the slf4j page it doesn't look like it would replace log4j - it would just allow you to use the same underlying logging framework (e.g. log4j) for your whole application, allowing libraries to hook into that automatically.
It looks more like a replacement for Apache Commons Logging than log4j.
回答5:
SLF4J has, in my opinion, the huge advantage that you can unify the logging of all the libraries that you use through the bridges that it provides. Neither of the other logging frameworks allows this. This allows projects to smoothly move to SLF4J and ignore the logging framework choices that dependencies have made.
回答6:
Slf4j is not a real logging facade. Slf4j does not support many features of its implementors. For short, I mention log4j examples below.
- Slf4j cannot specify a user selected configuration file, but forces user to use default (log4j.properties or log4j.xml) at one of so many Java roots (each Jar has one root plus JVM root and classes or bin). If two JAR files have it, it is hard to control which one to use safely.
- Slf4j cannot support all Log4j levels, such as 'fatal'. When switch big code from Log4j to Slf4j, huge code change effort is needed (e.g. deciding how to rearrange levels).
- Two key Jar files (log4j-over-slf4j.jar or slf4j-log4j12.jar) must be chosen. If classpath both, won't work. If choose one randomly, lose unexpected features (e.g. log4j-over-slf4j.jar does not support multiple log files for same classes; e.g. one for events log and one for raw data log).
来源：https://stackoverflow.com/questions/2063883/is-log4j-being-abandoned-in-favor-of-slf4j