Java SLF4J 线程安全吗？
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Is SLF4J thread-safe?
提问by
I might have a Dogclass that has a single instance shared across multiple threads. I plan on using SLF4J for all logging:
我可能有一个Dog类，它具有跨多个线程共享的单个实例。我计划使用 SLF4J 进行所有日志记录：
public class Dog {
private Logger logger = LoggerFactory.getLogger(Dog.class);
// ...etc.
}
Is my loggerinstance thread safe? Why/why not?
我的logger实例线程安全吗？为什么/为什么不？
采纳答案by Stephen C
In conclusion: LoggerFactory.getLogger(Class<?>)"caches" Loggerinstances based on class. So if I call LoggerFactory.getLogger(Dog.class)twice, I'll get 2 references to the same object in memory. This means that if 2+ threads instantiate a Dog, they'll both get the same (shared) Dog Loggerinstance.
总之：基于类LoggerFactory.getLogger(Class<?>)“缓存”Logger实例。所以如果我调用LoggerFactory.getLogger(Dog.class)两次，我会得到 2 个对内存中同一个对象的引用。这意味着如果 2+ 个线程实例化 a Dog，它们都将获得相同的（共享） DogLogger实例。
So the SLF4J API is notthread-safe.It's all up to the binding you choose. It looks like the common bindings (log4j, JUL and logback) are thread-safe, so even if multiple threads get access to the same Dog Logger, the log4j/JUL/logback logger binding is thread-safe, so you have no issues.
所以 SLF4J API不是线程安全的。这完全取决于您选择的绑定。看起来常见的绑定（log4j、JUL 和 logback）是线程安全的，所以即使多个线程访问同一个 Dog Logger，log4j/JUL/logback 记录器绑定也是线程安全的，所以你没有问题。
Case in point: if you are making your own SLF4J binding, make all your Loggerimpl methods synchronized, or address thread-safety in a different way (providing ThreadLocal, etc.).
举个例子：如果您要制作自己的 SLF4J 绑定，请制作所有Loggerimpl 方法synchronized，或者以不同的方式（提供ThreadLocal等）解决线程安全问题。
回答by Stephen C
Certainly, everyone assumesthat a Loggeris going to be thread-safe. But you would need to look at the code / javadocs of the implementation classes behind the facade to be absolutelysure.
当然，每个人都假设aLogger将是线程安全的。但是您需要查看外观背后的实现类的代码/javadoc 才能绝对确定。
For specific implementations:
具体实现：
- Log4j 1.2 is thread-safe
- java.util.logging.Logger is thread-safe(search for "multi-thread safe")
- Logback is thread-safe
(Obviously, these are statements that the respective code is designedto thread-safe. There can always be bugs. For example, there are currentlya couple of open thread-safety bugs in the Log4j 2 tracker, though it doesn't seem like those bugs would directly affect yourexample code.)
（显然，这些是相应代码被设计为线程安全的声明。总是有错误。例如，当前在Log4j 2 跟踪器中有几个开放的线程安全错误，尽管它看起来不像这些错误会直接影响您的示例代码。）
