fix the concurrent issue in SpringValueRegistry.scanAndClean

Author: nobodyiam

CHANGES.md

@@ -12,6 +12,7 @@ Apollo Java 2.4.0
 * [Feature Support Kubernetes ConfigMap cache for Apollo java, golang client](https://github.com/apolloconfig/apollo-java/pull/79)
 * [Feature support pulling configuration information from multiple AppIds](https://github.com/apolloconfig/apollo-java/pull/70)
 * [Fix monitor arg cause npe](https://github.com/apolloconfig/apollo-java/pull/86)
+* [Fix the concurrent issue in SpringValueRegistry.scanAndClean](https://github.com/apolloconfig/apollo-java/pull/95)
 
 ------------------
 All issues and pull requests are [here](https://github.com/apolloconfig/apollo-java/milestone/4?closed=1)

apollo-client/src/main/java/com/ctrip/framework/apollo/spring/property/SpringValueRegistry.java

@@ -84,12 +84,15 @@ private void scanAndClean() {
     Iterator<Multimap<String, SpringValue>> iterator = registry.values().iterator();
     while (!Thread.currentThread().isInterrupted() && iterator.hasNext()) {
       Multimap<String, SpringValue> springValues = iterator.next();
-      Iterator<Entry<String, SpringValue>> springValueIterator = springValues.entries().iterator();
-      while (springValueIterator.hasNext()) {
-        Entry<String, SpringValue> springValue = springValueIterator.next();
-        if (!springValue.getValue().isTargetBeanValid()) {
-          // clear unused spring values
-          springValueIterator.remove();
+      synchronized (springValues) {
+        Iterator<Entry<String, SpringValue>> springValueIterator = springValues.entries()
+            .iterator();
+        while (springValueIterator.hasNext()) {
+          Entry<String, SpringValue> springValue = springValueIterator.next();
+          if (!springValue.getValue().isTargetBeanValid()) {
+            // clear unused spring values
+            springValueIterator.remove();
+          }
         }
       }
     }