Issue #231: Possible infinite loop when initializing the ObjectDataType class

h2/src/docsrc/html/changelog.html

@@ -21,7 +21,8 @@ Change Log
 
 <h2>Next Version (unreleased)</h2>
 <ul>
-<li>-
+<li>Issue #231: Possible infinite loop when initializing the ObjectDataType class
+    when concurrently writing into MVStore.
 </li>
 </ul>
 

h2/src/main/org/h2/mvstore/type/ObjectDataType.java

@@ -332,8 +332,13 @@ public class ObjectDataType implements DataType {
         HashMap<Class<?>, Integer> map = COMMON_CLASSES_MAP;
         if (map.size() == 0) {
             // lazy initialization
+            // synchronized, because the COMMON_CLASSES_MAP is not
+            synchronized (map) {
+                if (map.size() == 0) {
                     for (int i = 0, size = COMMON_CLASSES.length; i < size; i++) {
-                COMMON_CLASSES_MAP.put(COMMON_CLASSES[i], i);
+                        map.put(COMMON_CLASSES[i], i);
+                    }
+                }
             }
         }
         return map.get(clazz);