修复MapUtil.computeIfAbsent可能存在的并发问题

hutool-core/src/main/java/cn/hutool/core/map/MapUtil.java

@@ -9,6 +9,7 @@ import cn.hutool.core.lang.Pair;
 import cn.hutool.core.lang.TypeReference;
 import cn.hutool.core.stream.CollectorUtil;
 import cn.hutool.core.util.ArrayUtil;
+import cn.hutool.core.util.JdkUtil;
 import cn.hutool.core.util.ReflectUtil;
 import cn.hutool.core.util.StrUtil;
 
@@ -1459,30 +1460,35 @@ public class MapUtil {
 	 */
 	public static <K, V> Map.Entry<K, V> entry(K key, V value, boolean isImmutable) {
 		return isImmutable ?
-				new AbstractMap.SimpleImmutableEntry<>(key, value) :
-				new AbstractMap.SimpleEntry<>(key, value);
+			new AbstractMap.SimpleImmutableEntry<>(key, value) :
+			new AbstractMap.SimpleEntry<>(key, value);
 	}
 
 	/**
 	 * 如果 key 对应的 value 不存在，则使用获取 mappingFunction 重新计算后的值，并保存为该 key 的 value，否则返回 value。<br>
 	 * 方法来自Dubbo，解决使用ConcurrentHashMap.computeIfAbsent导致的死循环问题。（issues#2349）<br>
 	 * A temporary workaround for Java 8 specific performance issue JDK-8161372 .<br>
-	 * This class should be removed once we drop Java 8 support.
+	 * This class should be removed once we drop Java 8 support.<br>
+	 * 参考：https://github.com/apache/dubbo/blob/3.2/dubbo-common/src/main/java/org/apache/dubbo/common/utils/ConcurrentHashMapUtils.java
 	 *
 	 * @param <K>             键类型
 	 * @param <V>             值类型
 	 * @param map             Map
 	 * @param key             键
 	 * @param mappingFunction 值不存在时值的生成函数
-	 * @see <a href="https://bugs.openjdk.java.net/browse/JDK-8161372">https://bugs.openjdk.java.net/browse/JDK-8161372</a>
 	 * @return 值
+	 * @see <a href="https://bugs.openjdk.java.net/browse/JDK-8161372">https://bugs.openjdk.java.net/browse/JDK-8161372</a>
 	 */
 	public static <K, V> V computeIfAbsent(Map<K, V> map, K key, Function<? super K, ? extends V> mappingFunction) {
-		V value = map.get(key);
-		if (null == value) {
-			map.putIfAbsent(key, mappingFunction.apply(key));
-			value = map.get(key);
+		if (JdkUtil.IS_JDK8) {
+			V value = map.get(key);
+			if (null == value) {
+				//map.putIfAbsent(key, mappingFunction.apply(key));
+				value = map.computeIfAbsent(key, mappingFunction);
+			}
+			return value;
+		} else {
+			return map.computeIfAbsent(key, mappingFunction);
 		}
-		return value;
 	}
 }

hutool-core/src/main/java/cn/hutool/core/util/JdkUtil.java

@@ -0,0 +1,86 @@
+/*
+ * Copyright (c) 2023 looly(loolly@aliyun.com)
+ * Hutool is licensed under Mulan PSL v2.
+ * You can use this software according to the terms and conditions of the Mulan PSL v2.
+ * You may obtain a copy of Mulan PSL v2 at:
+ *          http://license.coscl.org.cn/MulanPSL2
+ * THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
+ * EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
+ * MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
+ * See the Mulan PSL v2 for more details.
+ */
+
+package cn.hutool.core.util;
+
+/**
+ * JDK相关工具类，包括判断JDK版本等<br>
+ * 工具部分方法来自fastjson2的JDKUtils
+ *
+ * @author fastjson, looly
+ */
+public class JdkUtil {
+	/**
+	 * JDK版本
+	 */
+	public static final int JVM_VERSION;
+	/**
+	 * 是否JDK8<br>
+	 * 由于Hutool基于JDK8编译，当使用JDK版本低于8时，不支持。
+	 */
+	public static final boolean IS_JDK8;
+	/**
+	 * 是否大于等于JDK17
+	 */
+	public static final boolean IS_AT_LEAST_JDK17;
+
+	/**
+	 * 是否Android环境
+	 */
+	public static final boolean IS_ANDROID;
+
+	static {
+		// JVM版本
+		JVM_VERSION = _getJvmVersion();
+		IS_JDK8 = 8 == JVM_VERSION;
+		IS_AT_LEAST_JDK17 = JVM_VERSION >= 17;
+
+		// JVM名称
+		final String jvmName = _getJvmName();
+		IS_ANDROID = jvmName.equals("Dalvik");
+	}
+
+	/**
+	 * 获取JVM名称
+	 *
+	 * @return JVM名称
+	 */
+	private static String _getJvmName() {
+		return System.getProperty("java.vm.name");
+	}
+
+	/**
+	 * 根据{@code java.specification.version}属性值，获取版本号
+	 *
+	 * @return 版本号
+	 */
+	private static int _getJvmVersion() {
+		int jvmVersion = -1;
+
+		try{
+			String javaSpecVer = System.getProperty("java.specification.version");
+			if (StrUtil.isNotBlank(javaSpecVer)) {
+				if (javaSpecVer.startsWith("1.")) {
+					javaSpecVer = javaSpecVer.substring(2);
+				}
+				if (javaSpecVer.indexOf('.') == -1) {
+					jvmVersion = Integer.parseInt(javaSpecVer);
+				}
+			}
+		} catch (Throwable ignore){
+			// 默认JDK8
+			jvmVersion = 8;
+		}
+
+		return jvmVersion;
+	}
+}