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package org.macrocloud.kernel.toolkit.utils;

import org.springframework.lang.Nullable;

import java.util.HashMap;
import java.util.Map;
import java.util.function.Supplier;


/**
 * ThreadLocal 工具类,通过在ThreadLocal存储map信息,来实现在ThreadLocal中维护多个信息
 * 
e.g.
 * ThreadLocalUtils.put("key",value);

 * ThreadLocalUtils.get("key");

 * ThreadLocalUtils.remove("key");

 * ThreadLocalUtils.getAndRemove("key");

 * ThreadLocalUtils.get("key",()->defaultValue);

 * ThreadLocalUtils.clear();

 * 
 *
 * @author zhouhao
 * @since 2.0
 */
@SuppressWarnings("unchecked")
public class ThreadLocalUtil {
	
	/** The Constant LOCAL. */
	private static final ThreadLocal> LOCAL = ThreadLocal.withInitial(HashMap::new);

	/**
	 * Gets the all.
	 *
	 * @return threadLocal中的全部值
	 */
	public static Map getAll() {
		return new HashMap<>(LOCAL.get());
	}

	/**
	 * 设置一个值到ThreadLocal.
	 *
	 * @param    值的类型
	 * @param key   键
	 * @param value 值
	 * @return void
	 * @see Map#put(Object, Object)
	 */
	public static  T put(String key, T value) {
		LOCAL.get().put(key, value);
		return value;
	}

	/**
	 * 设置一个值到ThreadLocal.
	 *
	 * @param map map
	 * @see Map#putAll(Map)
	 */
	public static void put(Map map) {
		LOCAL.get().putAll(map);
	}

	/**
	 * 删除参数对应的值.
	 *
	 * @param key the key
	 * @see Map#remove(Object)
	 */
	public static void remove(String key) {
		LOCAL.get().remove(key);
	}

	/**
	 * 清空ThreadLocal.
	 *
	 * @see Map#clear()
	 */
	public static void clear() {
		LOCAL.remove();
	}

	/**
	 * 从ThreadLocal中获取值.
	 *
	 * @param  值泛型
	 * @param key 键
	 * @return T 值, 不存在则返回null, 如果类型与泛型不一致, 可能抛出{@link ClassCastException}
	 * @see Map#get(Object)
	 * @see ClassCastException
	 */
	@Nullable
	public static  T get(String key) {
		return ((T) LOCAL.get().get(key));
	}

	/**
	 * 从ThreadLocal中获取值,并指定一个当值不存在的提供者.
	 *
	 * @param  the generic type
	 * @param key the key
	 * @param supplierOnNull the supplier on null
	 * @return T the if absent
	 * @see Supplier
	 */
	@Nullable
	public static  T getIfAbsent(String key, Supplier supplierOnNull) {
		return ((T) LOCAL.get().computeIfAbsent(key, k -> supplierOnNull.get()));
	}

	/**
	 * 获取一个值后然后删除掉.
	 *
	 * @param  值类型
	 * @param key 键
	 * @return T
	 */
	public static  T getAndRemove(String key) {
		try {
			return get(key);
		} finally {
			remove(key);
		}
	}

}