! fix bug: WeakHashMap in Snapshot led to captured values GCed before replay unexpectedly

src/main/java/com/alibaba/ttl/TransmittableThreadLocal.java

@@ -3,6 +3,7 @@ package com.alibaba.ttl;
 import edu.umd.cs.findbugs.annotations.NonNull;
 import edu.umd.cs.findbugs.annotations.Nullable;
 
+import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.WeakHashMap;
@@ -371,16 +372,16 @@ public class TransmittableThreadLocal<T> extends InheritableThreadLocal<T> imple
             return new Snapshot(captureTtlValues(), captureThreadLocalValues());
         }
 
-        private static WeakHashMap<TransmittableThreadLocal<Object>, Object> captureTtlValues() {
-            WeakHashMap<TransmittableThreadLocal<Object>, Object> ttl2Value = new WeakHashMap<TransmittableThreadLocal<Object>, Object>();
+        private static HashMap<TransmittableThreadLocal<Object>, Object> captureTtlValues() {
+            HashMap<TransmittableThreadLocal<Object>, Object> ttl2Value = new HashMap<TransmittableThreadLocal<Object>, Object>();
             for (TransmittableThreadLocal<Object> threadLocal : holder.get().keySet()) {
                 ttl2Value.put(threadLocal, threadLocal.copyValue());
             }
             return ttl2Value;
         }
 
-        private static WeakHashMap<ThreadLocal<Object>, Object> captureThreadLocalValues() {
-            final WeakHashMap<ThreadLocal<Object>, Object> threadLocal2Value = new WeakHashMap<ThreadLocal<Object>, Object>();
+        private static HashMap<ThreadLocal<Object>, Object> captureThreadLocalValues() {
+            final HashMap<ThreadLocal<Object>, Object> threadLocal2Value = new HashMap<ThreadLocal<Object>, Object>();
             for (Map.Entry<ThreadLocal<Object>, TtlCopier<Object>> entry : threadLocalHolder.entrySet()) {
                 final ThreadLocal<Object> threadLocal = entry.getKey();
                 final TtlCopier<Object> copier = entry.getValue();
@@ -406,8 +407,8 @@ public class TransmittableThreadLocal<T> extends InheritableThreadLocal<T> imple
         }
 
         @NonNull
-        private static WeakHashMap<TransmittableThreadLocal<Object>, Object> replayTtlValues(@NonNull WeakHashMap<TransmittableThreadLocal<Object>, Object> captured) {
-            WeakHashMap<TransmittableThreadLocal<Object>, Object> backup = new WeakHashMap<TransmittableThreadLocal<Object>, Object>();
+        private static HashMap<TransmittableThreadLocal<Object>, Object> replayTtlValues(@NonNull HashMap<TransmittableThreadLocal<Object>, Object> captured) {
+            HashMap<TransmittableThreadLocal<Object>, Object> backup = new HashMap<TransmittableThreadLocal<Object>, Object>();
 
             for (final Iterator<TransmittableThreadLocal<Object>> iterator = holder.get().keySet().iterator(); iterator.hasNext(); ) {
                 TransmittableThreadLocal<Object> threadLocal = iterator.next();
@@ -432,8 +433,8 @@ public class TransmittableThreadLocal<T> extends InheritableThreadLocal<T> imple
             return backup;
         }
 
-        private static WeakHashMap<ThreadLocal<Object>, Object> replayThreadLocalValues(@NonNull WeakHashMap<ThreadLocal<Object>, Object> captured) {
-            final WeakHashMap<ThreadLocal<Object>, Object> backup = new WeakHashMap<ThreadLocal<Object>, Object>();
+        private static HashMap<ThreadLocal<Object>, Object> replayThreadLocalValues(@NonNull HashMap<ThreadLocal<Object>, Object> captured) {
+            final HashMap<ThreadLocal<Object>, Object> backup = new HashMap<ThreadLocal<Object>, Object>();
 
             for (Map.Entry<ThreadLocal<Object>, Object> entry : captured.entrySet()) {
                 final ThreadLocal<Object> threadLocal = entry.getKey();
@@ -456,9 +457,9 @@ public class TransmittableThreadLocal<T> extends InheritableThreadLocal<T> imple
          */
         @NonNull
         public static Object clear() {
-            final WeakHashMap<TransmittableThreadLocal<Object>, Object> ttl2Value = new WeakHashMap<TransmittableThreadLocal<Object>, Object>();
+            final HashMap<TransmittableThreadLocal<Object>, Object> ttl2Value = new HashMap<TransmittableThreadLocal<Object>, Object>();
 
-            final WeakHashMap<ThreadLocal<Object>, Object> threadLocal2Value = new WeakHashMap<ThreadLocal<Object>, Object>();
+            final HashMap<ThreadLocal<Object>, Object> threadLocal2Value = new HashMap<ThreadLocal<Object>, Object>();
             for (Map.Entry<ThreadLocal<Object>, TtlCopier<Object>> entry : threadLocalHolder.entrySet()) {
                 final ThreadLocal<Object> threadLocal = entry.getKey();
                 threadLocal2Value.put(threadLocal, threadLocalClearMark);
@@ -482,7 +483,7 @@ public class TransmittableThreadLocal<T> extends InheritableThreadLocal<T> imple
             restoreThreadLocalValues(backupSnapshot.threadLocal2Value);
         }
 
-        private static void restoreTtlValues(@NonNull WeakHashMap<TransmittableThreadLocal<Object>, Object> backup) {
+        private static void restoreTtlValues(@NonNull HashMap<TransmittableThreadLocal<Object>, Object> backup) {
             // call afterExecute callback
             doExecuteCallback(false);
 
@@ -501,14 +502,14 @@ public class TransmittableThreadLocal<T> extends InheritableThreadLocal<T> imple
             setTtlValuesTo(backup);
         }
 
-        private static void setTtlValuesTo(@NonNull WeakHashMap<TransmittableThreadLocal<Object>, Object> ttlValues) {
+        private static void setTtlValuesTo(@NonNull HashMap<TransmittableThreadLocal<Object>, Object> ttlValues) {
             for (Map.Entry<TransmittableThreadLocal<Object>, Object> entry : ttlValues.entrySet()) {
                 TransmittableThreadLocal<Object> threadLocal = entry.getKey();
                 threadLocal.set(entry.getValue());
             }
         }
 
-        private static void restoreThreadLocalValues(@NonNull WeakHashMap<ThreadLocal<Object>, Object> backup) {
+        private static void restoreThreadLocalValues(@NonNull HashMap<ThreadLocal<Object>, Object> backup) {
             for (Map.Entry<ThreadLocal<Object>, Object> entry : backup.entrySet()) {
                 final ThreadLocal<Object> threadLocal = entry.getKey();
                 threadLocal.set(entry.getValue());
@@ -516,10 +517,10 @@ public class TransmittableThreadLocal<T> extends InheritableThreadLocal<T> imple
         }
 
         private static class Snapshot {
-            final WeakHashMap<TransmittableThreadLocal<Object>, Object> ttl2Value;
-            final WeakHashMap<ThreadLocal<Object>, Object> threadLocal2Value;
+            final HashMap<TransmittableThreadLocal<Object>, Object> ttl2Value;
+            final HashMap<ThreadLocal<Object>, Object> threadLocal2Value;
 
-            private Snapshot(WeakHashMap<TransmittableThreadLocal<Object>, Object> ttl2Value, WeakHashMap<ThreadLocal<Object>, Object> threadLocal2Value) {
+            private Snapshot(HashMap<TransmittableThreadLocal<Object>, Object> ttl2Value, HashMap<ThreadLocal<Object>, Object> threadLocal2Value) {
                 this.ttl2Value = ttl2Value;
                 this.threadLocal2Value = threadLocal2Value;
             }