修复ReentrantCache的clear存在的外部资源泄露问题

hutool-cache/src/main/java/cn/hutool/cache/impl/ReentrantCache.java

@@ -1,8 +1,11 @@
 package cn.hutool.cache.impl;
 
 import cn.hutool.core.collection.CopiedIter;
+import cn.hutool.core.lang.mutable.Mutable;
 
+import java.util.HashSet;
 import java.util.Iterator;
+import java.util.Set;
 import java.util.concurrent.locks.ReentrantLock;
 
 /**
@@ -81,7 +84,14 @@ public abstract class ReentrantCache<K, V> extends AbstractCache<K, V> {
 	public void clear() {
 		lock.lock();
 		try {
-			cacheMap.clear();
+			// 获取所有键的副本
+			Set<Mutable<K>> keys = new HashSet<>(cacheMap.keySet());
+			for (Mutable<K> key : keys) {
+				CacheObj<K, V> co = removeWithoutLock(key.get());
+				if (co != null) {
+					onRemove(co.key, co.obj); // 触发资源释放
+				}
+			}
 		} finally {
 			lock.unlock();
 		}

hutool-cache/src/test/java/cn/hutool/cache/CacheTest.java

@@ -148,4 +148,26 @@ public class CacheTest {
 		assertFalse(ALARM_CACHE.containsKey(1));
 		assertEquals(1, counter.get());
 	}
+
+	/**
+	 * ReentrantCache类clear()方法、AbstractCache.putWithoutLock方法可能导致资源泄露
+	 * https://github.com/chinabugotech/hutool/issues/3957
+	 */
+	@Test
+	public void reentrantCache_clear_Method_Test() {
+		Cache<String, String> lruCache = CacheUtil.newLRUCache(4);
+		lruCache.setListener(new CacheListener<String, String>() {
+			@Override
+			public void onRemove(String key, String cachedObject) {
+				System.out.println(" listener key= "+ key+" value = "+cachedObject.toString()+" cachedObject资源释放操作...");
+			}
+		}  );
+		lruCache.put("key1","String1");
+		lruCache.put("key2","String2");
+		lruCache.put("key3","String3");
+		lruCache.put("key1","String4");//key已经存在，原始putWithoutLock方法存在资源泄露
+		lruCache.put("key4","String5");
+		lruCache.clear();//ReentrantCache类clear()方法存在资源泄露
+
+	}
 }