tweaks to PR #771 and merge

this change disables validation against the ID field when the field type is not "primitive like" and the idValue is an instance of DBObject suggesting that it's a complex key that has been converted to its DBObject form
(cherry picked from commit aef4b69)

morphia/src/main/java/org/mongodb/morphia/DatastoreImpl.java

@@ -51,6 +51,7 @@
 import org.mongodb.morphia.query.UpdateResults;
 import org.mongodb.morphia.utils.Assert;
 import org.mongodb.morphia.utils.IndexType;
+import org.mongodb.morphia.utils.ReflectionUtils;
 
 import java.lang.annotation.Annotation;
 import java.util.ArrayList;
@@ -1026,10 +1027,18 @@ protected <T> WriteResult tryVersionedUpdate(final DBCollection dbColl, final T
         mfVersion.setFieldValue(entity, newVersion);
 
         if (idValue != null && newVersion != 1) {
-            final UpdateResults res = update(
-                                                find(dbColl.getName(), entity.getClass()).filter(Mapper.ID_KEY, idValue)
-                                                                                         .filter(versionKeyName, oldVersion), dbObj,
-                                                false, false, wc);
+            final Query<?> query = find(dbColl.getName(), entity.getClass());
+            boolean compoundId = !ReflectionUtils.isPrimitiveLike(mc.getMappedIdField().getType())
+                                 && idValue instanceof DBObject;
+            if (compoundId) {
+                query.disableValidation();
+            }
+            query.filter(Mapper.ID_KEY, idValue);
+            if (compoundId) {
+                query.enableValidation();
+            }
+            query.filter(versionKeyName, oldVersion);
+            final UpdateResults res = update(query, dbObj, false, false, wc);
 
             wr = res.getWriteResult();
 

morphia/src/test/java/org/mongodb/morphia/mapping/CompoundIdTest.java

@@ -8,8 +8,11 @@
 import org.mongodb.morphia.AdvancedDatastore;
 import org.mongodb.morphia.TestBase;
 import org.mongodb.morphia.annotations.Embedded;
+import org.mongodb.morphia.annotations.Entity;
 import org.mongodb.morphia.annotations.Id;
 import org.mongodb.morphia.annotations.Reference;
+import org.mongodb.morphia.annotations.Version;
+import org.mongodb.morphia.dao.BasicDAO;
 
 import java.io.Serializable;
 
@@ -83,7 +86,108 @@ public int hashCode() {
         }
     }
 
+    public static class ConfigKey {
+        private String env;
+        private String subenv;
+        private String key;
 
+        public ConfigKey() {
+        }
+
+        public ConfigKey(final String env, final String key, final String subenv) {
+            this.env = env;
+            this.key = key;
+            this.subenv = subenv;
+        }
+
+        @Override
+        public boolean equals(final Object o) {
+            if (this == o) {
+                return true;
+            }
+            if (o == null || getClass() != o.getClass()) {
+                return false;
+            }
+
+            final ConfigKey configKey = (ConfigKey) o;
+
+            if (!env.equals(configKey.env)) {
+                return false;
+            }
+            if (!subenv.equals(configKey.subenv)) {
+                return false;
+            }
+            return key.equals(configKey.key);
+
+        }
+
+        @Override
+        public int hashCode() {
+            int result = env.hashCode();
+            result = 31 * result + subenv.hashCode();
+            result = 31 * result + key.hashCode();
+            return result;
+        }
+    }
+
+    @Entity(noClassnameStored = true)
+    public static class ConfigEntry {
+        @Id
+        private ConfigKey key;
+        private String value;
+        @Version
+        private long version;
+        private String lastModifiedUser;
+        private long lastModifiedMillis;
+
+        public ConfigEntry() {
+        }
+
+        public ConfigEntry(final ConfigKey key) {
+            this.key = key;
+        }
+
+        public ConfigKey getKey() {
+            return key;
+        }
+
+        public void setKey(final ConfigKey key) {
+            this.key = key;
+        }
+
+        public long getLastModifiedMillis() {
+            return lastModifiedMillis;
+        }
+
+        public void setLastModifiedMillis(final long lastModifiedMillis) {
+            this.lastModifiedMillis = lastModifiedMillis;
+        }
+
+        public String getLastModifiedUser() {
+            return lastModifiedUser;
+        }
+
+        public void setLastModifiedUser(final String lastModifiedUser) {
+            this.lastModifiedUser = lastModifiedUser;
+        }
+
+        public String getValue() {
+            return value;
+        }
+
+        public void setValue(final String value) {
+            this.value = value;
+        }
+
+        public long getVersion() {
+            return version;
+        }
+
+        public void setVersion(final long version) {
+            this.version = version;
+        }
+    }
+
     @Test
     public void testMapping() throws Exception {
         CompoundIdEntity entity = new CompoundIdEntity();
@@ -112,6 +216,15 @@ public void testOtherDelete() throws Exception {
         getDs().save(entity);
         ((AdvancedDatastore) getDs()).delete(getDs().getCollection(CompoundIdEntity.class).getName(), CompoundIdEntity.class, entity.id);
     }
+
+    @Test
+    public void testFetchKey() {
+        getDs().save(new ConfigEntry(new ConfigKey("env", "key", "subenv")));
+        BasicDAO<ConfigEntry, ConfigKey> innerDAO = new BasicDAO<ConfigEntry, ConfigKey>(ConfigEntry.class, getDs());
+        ConfigEntry entry = innerDAO.find().get();
+        entry.setValue("something");
+        innerDAO.save(entry);
+    }
 
     @Test
     @Ignore("https://github.com/mongodb/morphia/issues/675")