geode-core/src/main/java/org/apache/geode/cache/InterestPolicy.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.geode.cache;

import java.io.ObjectStreamException;

import org.apache.geode.annotations.Immutable;

/**
 * Enumerated type for region subscription interest policy. The interest policy specifies what data
 * a subscriber is interested in having in it's region.
 *
 *
 *
 * @see SubscriptionAttributes
 *
 * @since GemFire 5.0
 */
@Immutable
public class InterestPolicy implements java.io.Serializable {
  private static final long serialVersionUID = 1567179436331385968L;

  @Immutable
  private static final InterestPolicy[] VALUES = new InterestPolicy[2];

  /**
   * This subscriber is interested in all data. More specifically operations done in this cache and
   * distributed operations done in remote caches.
   * <p>
   * When combined with {@link DataPolicy#EMPTY} this region will receive events for every
   * distributed operation but will not store the data.
   * <p>
   * When combined with {@link DataPolicy#NORMAL} or {@link DataPolicy#PRELOADED} this region will
   * accept {@link Region#create(Object, Object)} operations done remotely. Without the
   * <code>ALL</code> interest policy, <code>NORMAL</code> and <code>PRELOADED</code> ignore
   * <code>creates</code> that the region does not have an existing entry for.
   * <p>
   * When combined with the {@link DataPolicy#withReplication replication policies} this interest
   * has no effect.
   * <p>
   * When combined with {@link DataPolicy#PARTITION} this interest policy causes cache listeners to
   * be notified of changes regardless of the physical location of the data affected. That is, a
   * listener in a VM using this policy will receive notification of all changes to the partitioned
   * region.
   */
  @Immutable
  public static final InterestPolicy ALL = new InterestPolicy("ALL", 0);

  /**
   * This subscriber is interested in data that is already in its cache. More specifically
   * operations done in this cache and distributed operations done in remote caches.
   * <p>
   * When combined with {@link DataPolicy#EMPTY} this region will never receive events for
   * distributed operations since its content is always empty. It will continue to get events for
   * operations done locally.
   * <p>
   * When combined with {@link DataPolicy#NORMAL} or {@link DataPolicy#PRELOADED} this region will
   * accept remote operations done to entries it already has in its cache.
   * <p>
   * When combined with the {@link DataPolicy#withReplication replication policies} * this interest
   * has no effect.
   * <p>
   * When combined with {@link DataPolicy#PARTITION} this interest policy causes cache listeners to
   * be notified in the VM holding the affected data. That is, listeners are only notified if the
   * affected* key-value pair is in the same process as the listener.
   */
  @Immutable
  public static final InterestPolicy CACHE_CONTENT = new InterestPolicy("CACHE_CONTENT", 1);

  /**
   * The interest policy used by default; it is {@link #CACHE_CONTENT}.
   */
  @Immutable
  public static final InterestPolicy DEFAULT = CACHE_CONTENT;


  /** The name of this mirror type. */
  private final transient String name;

  /** used as ordinal to represent this InterestPolicy */
  public final byte ordinal;

  private Object readResolve() throws ObjectStreamException {
    return VALUES[ordinal]; // Canonicalize
  }


  /** Creates a new instance of InterestPolicy. */
  private InterestPolicy(String name, int ordinal) {
    this.name = name;
    this.ordinal = (byte) ordinal;
    VALUES[this.ordinal] = this;
  }

  /** Return the InterestPolicy represented by specified ordinal */
  public static InterestPolicy fromOrdinal(byte ordinal) {
    return VALUES[ordinal];
  }


  /**
   * Return true if this policy is {@link #ALL}.
   *
   * @return true if this policy is {@link #ALL}.
   */
  public boolean isAll() {
    return this == ALL;
  }

  /**
   * Return true if this policy is {@link #CACHE_CONTENT}.
   *
   * @return true if this policy is {@link #CACHE_CONTENT}.
   */
  public boolean isCacheContent() {
    return this == CACHE_CONTENT;
  }

  /**
   * Return true if this policy is the default.
   *
   * @return true if this policy is the default.
   */
  public boolean isDefault() {
    return this == DEFAULT;
  }

  /**
   * Returns a string representation for this interest policy.
   *
   * @return the name of this interest policy.
   */
  @Override
  public String toString() {
    return this.name;
  }
}