ThreadLocal记录日志

import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import trace.visitor.Visitor;

public class Trace {
	private static ThreadLocal<ConcurrentHashMap<Class<? extends ITracer>, ITracer>> tracer = new ThreadLocal<ConcurrentHashMap<Class<? extends ITracer>, ITracer>>() {
		@Override
		protected ConcurrentHashMap<Class<? extends ITracer>, ITracer> initialValue() {
			return new ConcurrentHashMap<Class<? extends ITracer>, ITracer>();
		}
	};
	private static ThreadLocal<Boolean> lock = new ThreadLocal<Boolean>() {
		@Override
		protected Boolean initialValue() {
			return Boolean.FALSE;
		}
	};

	public static boolean isStart() {
		return lock.get();
	}

	public static void start() {
		lock.set(true);
	}

	public static void stop() {
		lock.set(false);
	}

	public static void trace(Visitor visitor, ITraceFilter filter) {

		if (visitor == null) {
			throw new NullPointerException("需要先指定访问者");
		}
		ConcurrentHashMap<Class<? extends ITracer>, ITracer> map = tracer.get();
		for (Map.Entry<Class<? extends ITracer>, ITracer> entry : map
				.entrySet()) {
			ITracer tracer = entry.getValue();
			List<? extends AbstractEntry> entrys = tracer.getEntrySet();
			for (AbstractEntry e : entrys) {
				if (filter == null || filter.accept(e)) {
					e.accept(visitor);
				}
			}
		}

	}

	public static void trace(Visitor visitor) {
		trace(visitor, null);
	}

	public static void reset() {
		ConcurrentHashMap<Class<? extends ITracer>, ITracer> map = tracer.get();
		for (Map.Entry<Class<? extends ITracer>, ITracer> entry : map
				.entrySet()) {
			ITracer tracer = entry.getValue();
			tracer.reset();
		}
	}

	@SuppressWarnings("unchecked")
	public static <T extends ITracer> T getTracer(Class<T> clazz) {
		ConcurrentHashMap<Class<? extends ITracer>, ITracer> map = tracer.get();
		try {
			map.putIfAbsent(clazz, (T) clazz.newInstance());
			return (T) map.get(clazz);
		} catch (Exception e) {
			throw new RuntimeException("无法获取" + clazz.getName() + "的记录器");
		}
	}
}

 

获取一个tracer，调用tracer.debug（×××），记录的东西都保存在ThreadLocal中，最后通过访问者模式暴露给外部使用。可以用来统计方法运行过程中产生的各种日志，以及方法执行的时间，结果等等