io.cdap.cdap.pipeline.Context Maven / Gradle / Ivy
/*
* Copyright © 2014 Cask Data, Inc.
*
* 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 io.cdap.cdap.pipeline;
import java.util.Set;
import javax.annotation.Nullable;
/**
* This interface represents the context in which a stage is running.
* Ordinarily the context will be provided by the pipeline in which
* the stage is embedded.
*/
public interface Context {
/**
* Used when you a {@link Stage} wants to send data to the downstream stage
*
* @param o to be send to next stage.
*/
void setDownStream(Object o);
/**
* @return Object passed through from the upstream
*/
Object getUpStream();
/**
* @return Object being send to downstream
*/
Object getDownStream();
/**
* Returns a property value associated with the given key that was set by {@link #setProperty(String, Object)} call.
*
* @param key the property key
* @param type of the value
* @return the value or {@code null} if no such property.
*/
@Nullable
T getProperty(String key);
/**
* Sets a value for the given property.
*
* @param key the property key
* @param value the property value
* @param type of the value.
*/
void setProperty(String key, T value);
/**
* Returns the set of property keys in this context.
*/
Set getPropertyKeys();
}