* Copyright 2007 Daniel Spiewak
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
Marks a method such that the corresponding database field will be the primary key for the table in question. Using this annotation, it is possible to specify arbitrary primary key field names and types.
The logic in both migrations and entity invocation handling assumes
that there is only a single primary key per entity type. If the entity
type does not contain exactly one field (may be more than one method)
as a primary key, odd errors will ensue. Primary keys need not be
defined within the entity type itself. For example, most entities
inherit from the
interface, which defines the
id field as the primary key. Such entities would not
have to (in fact, should not at all) explicitly define a primary key