reverts commit 4d7929cf

mybatis-plus-core/src/main/java/com/baomidou/mybatisplus/core/toolkit/ReflectionKit.java

@@ -214,7 +214,14 @@ public final class ReflectionKit {
         if (Objects.isNull(clazz)) {
             return Collections.emptyList();
         }
-        return CLASS_FIELD_CACHE.computeIfAbsent(clazz, ReflectionKit::doGetFieldList);
+        List<Field> fields = CLASS_FIELD_CACHE.get(clazz);
+        if (CollectionUtils.isEmpty(fields)) {
+            synchronized (CLASS_FIELD_CACHE) {
+                fields = doGetFieldList(clazz);
+                CLASS_FIELD_CACHE.put(clazz, fields);
+            }
+        }
+        return fields;
     }
 
     /**