Support for Generic entities

Update most of the entityManager methods to support receiving an extra
ParameterizedType in case the user need to persist a Generic entity.

The type lost by erasure will then be reified using the informations
from the Parameterized type and the fields will be introspected as
normal.

Previous behaviour is not impacted and no breaking change was needed.

src/main/java/com/jmethods/catatumbo/DatastoreBatch.java

@@ -16,6 +16,7 @@
 
 package com.jmethods.catatumbo;
 
+import java.lang.reflect.Type;
 import java.util.List;
 
 /**
@@ -31,7 +32,7 @@ public interface DatastoreBatch {
    * Adds the given entity to this batch for insertion. If the entity does not have an identifier
    * set, ID may be automatically generated. If the same entity was added to this batch for
    * deletion, the insert request is changed into an upsert request.
-   * 
+   *
    * @param entity
    *          the entity to insert.
    * @return the inserted entity. The inserted entity may not be same as the passed in entity. For
@@ -41,6 +42,22 @@ public interface DatastoreBatch {
    */
   <E> E insert(E entity);
 
+  /**
+   * Adds the given entity to this batch for insertion. If the entity does not have an identifier
+   * set, ID may be automatically generated. If the same entity was added to this batch for
+   * deletion, the insert request is changed into an upsert request.
+   *
+   * @param entity
+   *          the entity to insert.
+   * @param entityType
+   *          the entity type
+   * @return the inserted entity. The inserted entity may not be same as the passed in entity. For
+   *         example, the inserted entity may contain any generated ID, key, parent key, etc.
+   * @throws EntityManagerException
+   *           if any error occurs while inserting.
+   */
+  <E> E insert(E entity, Type entityType);
+
   /**
    * Adds the given entities to this batch for insertion. If any of the entities do not have an
    * identifier set, ID may be generated automatically. If any of entities were added to this batch
@@ -55,6 +72,22 @@ public interface DatastoreBatch {
    */
   <E> List<E> insert(List<E> entities);
 
+  /**
+   * Adds the given entities to this batch for insertion. If any of the entities do not have an
+   * identifier set, ID may be generated automatically. If any of entities were added to this batch
+   * for deletion, the insert request is changed to an upsert request.
+   *
+   * @param entities
+   *          the entities to insert.
+   * @param entityType
+   *          the entity type
+   * @return the inserted entities. The inserted entities may not be same as the passed in entities.
+   *         For example, the inserted entities may contain generated ID, key, parent key, etc.
+   * @throws EntityManagerException
+   *           if any error occurs while inserting.
+   */
+  <E> List<E> insert(List<E> entities, Type entityType);
+
   /**
    * Adds the given entity to this batch for insertion. The ID allocation is deferred to the submit
    * time of this batch. Generated keys can be retrieved using
@@ -70,6 +103,23 @@ public interface DatastoreBatch {
    */
   <E> void insertWithDeferredIdAllocation(E entity);
 
+  /**
+   * Adds the given entity to this batch for insertion. The ID allocation is deferred to the submit
+   * time of this batch. Generated keys can be retrieved using
+   * {@link DatastoreBatch.Response#getGeneratedKeys()}.This method throws
+   * {@link EntityManagerException} if the entity is using a String identifier. String identifiers
+   * are allocated at add time, instead of submit time. For entities with String identifiers, use
+   * the {@link DatastoreBatch#insert(Object)} method.
+   *
+   * @param entity
+   *          the entity to insert
+   * @param entityType
+   *          the entity type
+   * @throws EntityManagerException
+   *           if the entity has a String identifier or if any error occurs
+   */
+  <E> void insertWithDeferredIdAllocation(E entity, Type entityType);
+
   /**
    * Adds the given entities to this batch for insertion. The ID allocation is deferred to the
    * submit time of this batch. Generated keys can be retrieved using
@@ -85,6 +135,23 @@ public interface DatastoreBatch {
    */
   <E> void insertWithDeferredIdAllocation(List<E> entities);
 
+  /**
+   * Adds the given entities to this batch for insertion. The ID allocation is deferred to the
+   * submit time of this batch. Generated keys can be retrieved using
+   * {@link DatastoreBatch.Response#getGeneratedKeys()}.This method throws
+   * {@link EntityManagerException} if the entity is using a String identifier. String identifiers
+   * are allocated at add time, instead of submit time. For entities with String identifiers, use
+   * the {@link DatastoreBatch#insert(List)} method.
+   *
+   * @param entities
+   *          the entities to insert
+   * @param entityType
+   *          the entity type
+   * @throws EntityManagerException
+   *           if the entity have a String identifier any error occurs
+   */
+  <E> void insertWithDeferredIdAllocation(List<E> entities, Type entityType);
+
   /**
    * Adds the given entity to this batch for update. The operation will fail if the entity with the
    * same key does not exist in the underlying Datastore. This method does not use optimistic
@@ -98,6 +165,21 @@ public interface DatastoreBatch {
    */
   <E> E update(E entity);
 
+  /**
+   * Adds the given entity to this batch for update. The operation will fail if the entity with the
+   * same key does not exist in the underlying Datastore. This method does not use optimistic
+   * locking even if the given entity has a field with {@link Version} annotation.
+   *
+   * @param entity
+   *          the entity to update
+   * @param entityType
+   *          the entity type
+   * @return the updated entity.
+   * @throws EntityManagerException
+   *           if any error occurs while updating.
+   */
+  <E> E update(E entity, Type entityType);
+
   /**
    * Adds the given entities to this batch for update. The operation will fail if the entities with
    * the same key do not already exist in the underlying datastore. This method does not use
@@ -112,6 +194,22 @@ public interface DatastoreBatch {
    */
   <E> List<E> update(List<E> entities);
 
+  /**
+   * Adds the given entities to this batch for update. The operation will fail if the entities with
+   * the same key do not already exist in the underlying datastore. This method does not use
+   * optimistic locking even if the given entity has a field with {@link Version} annotation.
+   *
+   *
+   * @param entities
+   *          the entities to update.
+   * @param entityType
+   *          the entity type
+   * @return the updated entities
+   * @throws EntityManagerException
+   *           if any error occurs while inserting.
+   */
+  <E> List<E> update(List<E> entities, Type entityType);
+
   /**
    * Adds the given entity to this batch for update or insert. Any prior writes to this entity in
    * this batch will be removed from this batch. If the entity does not have an ID set, ID may be
@@ -125,6 +223,21 @@ public interface DatastoreBatch {
    */
   <E> E upsert(E entity);
 
+  /**
+   * Adds the given entity to this batch for update or insert. Any prior writes to this entity in
+   * this batch will be removed from this batch. If the entity does not have an ID set, ID may be
+   * generated automatically.
+   *
+   * @param entity
+   *          the entity to update or insert
+   * @param entityType
+   *          the entity type
+   * @return the updated/inserted entity.
+   * @throws EntityManagerException
+   *           if any error occurs while saving.
+   */
+  <E> E upsert(E entity, Type entityType);
+
   /**
    * Adds the given entities to this batch for update or insert. Any prior writes of any of the
    * entities will be removed from this batch. If any of the entities do not have their IDs set, IDs
@@ -138,6 +251,21 @@ public interface DatastoreBatch {
    */
   <E> List<E> upsert(List<E> entities);
 
+  /**
+   * Adds the given entities to this batch for update or insert. Any prior writes of any of the
+   * entities will be removed from this batch. If any of the entities do not have their IDs set, IDs
+   * may be generated automatically.
+   *
+   * @param entities
+   *          the entities to update/or insert.
+   * @param entityType
+   *          the entity type
+   * @return the updated or inserted entities
+   * @throws EntityManagerException
+   *           if any error occurs while saving.
+   */
+  <E> List<E> upsert(List<E> entities, Type entityType);
+
   /**
    * Adds the given entity to this batch for insert or update. The ID (for numeric ID) allocation
    * will be deferred to the submit time of this batch. This method throws an
@@ -152,6 +280,22 @@ public interface DatastoreBatch {
    */
   <E> void upsertWithDeferredIdAllocation(E entity);
 
+  /**
+   * Adds the given entity to this batch for insert or update. The ID (for numeric ID) allocation
+   * will be deferred to the submit time of this batch. This method throws an
+   * {@link EntityManagerException} if the entity is using a String ID. Entity with String ID should
+   * use {@link DatastoreBatch#upsert(Object)} method.
+   *
+   * @param entity
+   *          the entity to update or insert
+   * @param entityType
+   *          the entity type
+   * @throws EntityManagerException
+   *           if the entity has a String ID or any other error occurs while accessing the
+   *           underlying datastore.
+   */
+  <E> void upsertWithDeferredIdAllocation(E entity, Type entityType);
+
   /**
    * Adds the given entities to this batch for update or insert. The ID (for numeric ID) allocation
    * will be deferred to the submit time of this batch. This method throws an
@@ -166,6 +310,22 @@ public interface DatastoreBatch {
    */
   <E> void upsertWithDeferredIdAllocation(List<E> entities);
 
+  /**
+   * Adds the given entities to this batch for update or insert. The ID (for numeric ID) allocation
+   * will be deferred to the submit time of this batch. This method throws an
+   * {@link EntityManagerException} if the entities have String identifiers. Entities with String
+   * identifiers should use {@link DatastoreBatch#upsert(List)} method.
+   *
+   * @param entities
+   *          the entities to update or insert
+   * @param entityType
+   *          the entity type
+   * @throws EntityManagerException
+   *           if the entities have String identifiers or any other error occurs while accessing the
+   *           underlying datastore.
+   */
+  <E> void upsertWithDeferredIdAllocation(List<E> entities, Type entityType);
+
   /**
    * Adds the given entity to this batch for deletion.
    * 
@@ -176,6 +336,18 @@ public interface DatastoreBatch {
    */
   void delete(Object entity);
 
+  /**
+   * Adds the given entity to this batch for deletion.
+   *
+   * @param entity
+   *          the entity to delete.
+   * @param entityType
+   *          the entity type
+   * @throws EntityManagerException
+   *           if any error occurs while deleting.
+   */
+  void delete(Object entity, Type entityType);
+
   /**
    * Adds the given entities to this batch for deletion.
    * 
@@ -186,57 +358,69 @@ public interface DatastoreBatch {
    */
   void delete(List<?> entities);
 
+  /**
+   * Adds the given entities to this batch for deletion.
+   *
+   * @param entities
+   *          the entities to delete.
+   * @param entityType
+   *          the entity type
+   * @throws EntityManagerException
+   *           if any error occurs while deleting.
+   */
+  void delete(List<?> entities, Type entityType);
+
   /**
    * Adds the given ID and entity type to this batch for deletion.
    * 
-   * @param entityClass
-   *          the entity class.
+   * @param entityType
+   *          the entity type.
    * @param id
    *          the ID of the entity.
    * @throws EntityManagerException
    *           if any error occurs while inserting.
    */
-  <E> void delete(Class<E> entityClass, long id);
+  <E> void delete(Type entityType, long id);
 
   /**
    * Adds the given ID and entity type to this batch for deletion.
    * 
-   * @param entityClass
-   *          the entity class.
+   * @param entityType
+   *          the entity type.
    * @param id
    *          the ID of the entity.
    * @throws EntityManagerException
    *           if any error occurs while inserting.
    */
-  <E> void delete(Class<E> entityClass, String id);
+  <E> void delete(Type entityType, String id);
 
   /**
    * Adds the given entity type, parent key and ID to this batch for deletion.
    * 
-   * @param entityClass
-   *          the entity class.
+   * @param entityType
+   *          the entity type.
    * @param parentKey
    *          the parent key
    * @param id
    *          the ID of the entity.
    * @throws EntityManagerException
    *           if any error occurs while inserting.
    */
-  <E> void delete(Class<E> entityClass, DatastoreKey parentKey, long id);
+  <E> void delete(Type entityType, DatastoreKey parentKey, long id);
 
   /**
    * Adds the given entity type, parent key and ID to this batch for deletion.
    * 
-   * @param entityClass
-   *          the entity class.
+   * @param entityType
+   *          the entity type.
    * @param parentKey
    *          the parent key
    * @param id
    *          the ID of the entity.
    * @throws EntityManagerException
    *           if any error occurs while inserting.
    */
-  <E> void delete(Class<E> entityClass, DatastoreKey parentKey, String id);
+  <E> void delete(Type entityType, DatastoreKey parentKey, String id);
 
   /**
    * Adds the given key to this batch for deletion.
@@ -250,7 +434,7 @@ public interface DatastoreBatch {
 
   /**
    * Adds the given keys to this batch for deletion.
-   * 
+   *
    * @param keys
    *          the keys to delete
    * @throws EntityManagerException