Added a unit test for issue 81.

src/test/java/com/fasterxml/jackson/dataformat/xml/types/TestPolymorphic.java

@@ -1,6 +1,11 @@
 package com.fasterxml.jackson.dataformat.xml.types;
 
+import java.util.ArrayList;
+import java.util.List;
+
+import com.fasterxml.jackson.annotation.JsonIdentityInfo;
 import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.fasterxml.jackson.annotation.ObjectIdGenerators;
 import com.fasterxml.jackson.dataformat.xml.XmlMapper;
 import com.fasterxml.jackson.dataformat.xml.XmlTestBase;
 
@@ -36,6 +41,20 @@ public SubTypeWithClassObject() { }
         public SubTypeWithClassObject(String s) { name = s; }
     }
 
+    @JsonTypeInfo(use = JsonTypeInfo.Id.CLASS, include = JsonTypeInfo.As.PROPERTY)
+    @JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "id")
+    protected static class TypeWithClassPropertyAndObjectId {
+        public String id;
+
+        public TypeWithClassPropertyAndObjectId(String id) { this.id = id; }
+    }
+
+    protected static class Wrapper {
+        public List<TypeWithClassPropertyAndObjectId> data;
+
+        public Wrapper(List<TypeWithClassPropertyAndObjectId> data) { this.data = data; }
+    }
+
     /*
     /**********************************************************
     /* Set up
@@ -86,5 +105,21 @@ public void testAsClassObject() throws Exception
         assertEquals(SubTypeWithClassObject.class, result.getClass());
         assertEquals("Foobar", ((SubTypeWithClassObject) result).name);
     }
+
+    /**
+     * Test for issue 81
+     */
+    public void testAsPropertyWithObjectId() throws Exception {
+        List<TypeWithClassPropertyAndObjectId> data = new ArrayList<TestPolymorphic.TypeWithClassPropertyAndObjectId>();
+        TypeWithClassPropertyAndObjectId object = new TypeWithClassPropertyAndObjectId("Foobar");
+        data.add(object);
+        // This will be written as an id reference instead of object; as such, no type info will be written.
+        data.add(object);
+        String xml = _xmlMapper.writeValueAsString(new Wrapper(data));
+        Wrapper result = _xmlMapper.readValue(xml, Wrapper.class);
+        assertNotNull(result);
+        assertSame(result.data.get(0), result.data.get(1));
+        assertEquals("Foobar", result.data.get(0).id);
+    }
 }