org.immutables.criteria.backend.Backend Maven / Gradle / Ivy
/*
* Copyright 2019 Immutables Authors and Contributors
*
* 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
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* 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.
*/
package org.immutables.criteria.backend;
import org.reactivestreams.Publisher;
/**
* Abstraction of a asynchronous service used by different clients.
* Example of backend: database, REST service or file system.
*/
public interface Backend {
/**
* Open a session (or reuse existing one) with a given context
*
* @param entityType entity entityType for which to open a session
* @return new session
*/
Session open(Class entityType);
/**
* Generic operation to be executed on the back-end. Typical operations include
* query, update, delete etc.
*/
interface Operation { }
/**
* Context specific "connection" to the back-end. Typically creates isolated view on a table,
* collection (mongo) or class.
*/
interface Session {
Class entityType();
/**
* Apply an operation on the back-end. {@code operation} in this context can mean query / update
* / insert / index etc.
*
*
* @param operation operation to be performed on the back-end.
* @return result of the operation
*/
Result execute(Operation operation);
}
/**
* Result of an operation which gives access to stream of events
*/
interface Result {
/**
* Depending on operation, publisher can represent empty, single, multiple or unbounded event flow.
*
* @return empty, single, multiple or unbounded event flow
*/
Publisher publisher();
}
}