[FIXED HUDSON-8006] fix serialization of array containing null elements,

based on patch from alexlehm


git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@36992 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/util/XStream2.java

@@ -113,7 +113,7 @@ public class XStream2 extends XStream {
         Mapper m = new CompatibilityMapper(new MapperWrapper(next) {
             @Override
             public String serializedClass(Class type) {
-                if (ImmutableMap.class.isAssignableFrom(type))
+                if (type != null && ImmutableMap.class.isAssignableFrom(type))
                     return super.serializedClass(ImmutableMap.class);
                 else
                     return super.serializedClass(type);

core/src/test/java/hudson/util/XStream2Test.java

@@ -164,4 +164,10 @@ public class XStream2Test extends TestCase {
         assertSame(m.getClass(),a.m.getClass());    // should get back the exact same type, not just a random map
         assertEquals(m,a.m);
     }
+
+    // @Bug(8006) -- Previously a null entry in an array caused NPE
+    public void testEmptyStack() {
+        assertEquals("<object-array><null/><null/></object-array>",
+                     Run.XSTREAM.toXML(new Object[2]).replaceAll("[ \n\r\t]+", ""));
+    }
 }