samza-core/src/main/java/org/apache/samza/context/InternalTaskContext.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.samza.context;

import org.apache.samza.job.model.JobModel;
import org.apache.samza.system.StreamMetadataCache;
import org.apache.samza.system.SystemStreamPartition;

import java.util.HashMap;
import java.util.Map;
import java.util.Set;


/**
 * This class is used for passing objects around for the implementation of the high-level API.
 * 1) Container for objects that need to be passed between different components in the implementation of the high-level
 * API.
 * 2) The implementation of the high-level API is built on top of the low-level API. The low-level API only exposes
 * {@link TaskContext}, but the implementation of the high-level API needs some other internal Samza components (e.g.
 * {@link StreamMetadataCache}. We internally make these components available through {@link TaskContextImpl} so that we
 * can do a cast to access the components. This class hides some of the messiness of casting. It's still not ideal to
 * need to do any casting, even in this class.
 */
public class InternalTaskContext {
  private final Context context;
  private final Map<String, Object> objectRegistry = new HashMap<>();

  public InternalTaskContext(Context context) {
    this.context = context;
  }

  public void registerObject(String name, Object value) {
    this.objectRegistry.put(name, value);
  }

  public Object fetchObject(String name) {
    return this.objectRegistry.get(name);
  }

  public Context getContext() {
    return context;
  }

  /**
   * TODO: The public {@link JobContext} exposes {@link JobModel} now, so can this internal method be replaced by the
   * public API?
   */
  public JobModel getJobModel() {
    return ((TaskContextImpl) this.context.getTaskContext()).getJobModel();
  }

  public StreamMetadataCache getStreamMetadataCache() {
    return ((TaskContextImpl) this.context.getTaskContext()).getStreamMetadataCache();
  }

  /**
   * See {@link TaskContextImpl#getSspsExcludingSideInputs()}.
   */
  public Set<SystemStreamPartition> getSspsExcludingSideInputs() {
    return ((TaskContextImpl) this.context.getTaskContext()).getSspsExcludingSideInputs();
  }
}