api: Implement findByXId in GenericDaoBase and EntityManagerImpl

Declare and define findByXId() in GenericDao and EntityManager.
This method would return a VO by UUID and EntityManager's interface would
take in the VO Interface.

Signed-off-by: Rohit Yadav <bhaisaab@apache.org>

api/src/com/cloud/dao/EntityManager.java

@@ -45,7 +45,7 @@ public interface EntityManager {
      * @param xid external id
      * @return T if found, null if not.
      */
-    public <T> T findByXid(Class<T> entityType, String xid);
+    public <T> T findByXId(Class<T> entityType, String xid);
 
     /**
      * Lists all entities.  Use this method at your own risk.

server/src/com/cloud/dao/EntityManagerImpl.java

@@ -45,8 +45,9 @@ public class EntityManagerImpl implements EntityManager, Manager {
     }
 
     @Override
-    public <T> T findByXid(Class<T> entityType, String xid) {
-        return null;
+    public <T> T findByXId(Class<T> entityType, String xid) {
+        GenericDao<? extends T, String> dao = (GenericDao<? extends T, String>)GenericDaoBase.getDao(entityType);
+        return dao.findByXId(xid);
     }
 
     @Override

utils/src/com/cloud/utils/db/GenericDao.java

@@ -54,6 +54,9 @@ public interface GenericDao<T, ID extends Serializable> {
     T findByIdIncludingRemoved(ID id);
     
     T findById(ID id, boolean fresh);
+
+    // Finds a VO object using uuid
+    T findByXId(ID uuid);
     
     /**
      * @return VO object ready to be used for update.  It won't have any fields filled in.

utils/src/com/cloud/utils/db/GenericDaoBase.java

@@ -913,6 +913,14 @@ public abstract class GenericDaoBase<T, ID extends Serializable> implements Gene
         }
     }
 
+    @Override @DB(txn=false)
+    @SuppressWarnings("unchecked")
+    public T findByXId(final ID uuid) {
+        SearchCriteria<T> sc = createSearchCriteria();
+        sc.addAnd("uuid", SearchCriteria.Op.EQ, uuid);
+        return findOneBy(sc);
+    }
+
     @Override @DB(txn=false)
     public T findByIdIncludingRemoved(ID id) {
         return findById(id, true, null);