如下两个类，EventType和KeeperState，是ZooKeeper源码中枚举类的实现方法：
public enum EventType { // 事件类型 // 无 None (-1), // 结点创建 NodeCreated (1), // 结点删除 NodeDeleted (2), // 结点数据变化 NodeDataChanged (3), // 结点子节点变化 NodeChildrenChanged (4); // 代表事件类型的整形 private final int intValue; // Integer representation of value // for sending over wire // 构造函数 EventType(int intValue) { this.intValue = intValue; } // 返回整形 public int getIntValue() { return intValue; } // 从整形构造相应的事件 public static EventType fromInt(int intValue) { switch(intValue) { case -1: return EventType.None; case 1: return EventType.NodeCreated; case 2: return EventType.NodeDeleted; case 3: return EventType.NodeDataChanged; case 4: return EventType.NodeChildrenChanged; default: throw new RuntimeException("Invalid integer value for conversion to EventType"); } } } } public enum KeeperState { // 事件发生时Zookeeper的状态 /** Unused, this state is never generated by the server */ @Deprecated // 未知状态，不再使用，服务器不会产生此状态 Unknown (-1), /** The client is in the disconnected state - it is not connected * to any server in the ensemble. */ // 断开 Disconnected (0), /** Unused, this state is never generated by the server */ @Deprecated // 未同步连接，不再使用，服务器不会产生此状态 NoSyncConnected (1), /** The client is in the connected state - it is connected * to a server in the ensemble (one of the servers specified * in the host connection parameter during ZooKeeper client * creation). */ // 同步连接状态 SyncConnected (3), /** * Auth failed state */ // 认证失败状态 AuthFailed (4), /** * The client is connected to a read-only server, that is the * server which is not currently connected to the majority. * The only operations allowed after receiving this state is * read operations. * This state is generated for read-only clients only since * read/write clients aren't allowed to connect to r/o servers. */ // 只读连接状态 ConnectedReadOnly (5), /** * SaslAuthenticated: used to notify clients that they are SASL-authenticated, * so that they can perform Zookeeper actions with their SASL-authorized permissions. */ // SASL认证通过状态 SaslAuthenticated(6), /** The serving cluster has expired this session. The ZooKeeper * client connection (the session) is no longer valid. You must * create a new client connection (instantiate a new ZooKeeper * instance) if you with to access the ensemble. */ // 过期状态 Expired (-112); // 代表状态的整形值 private final int intValue; // Integer representation of value // for sending over wire // 构造函数 KeeperState(int intValue) { this.intValue = intValue; } // 返回整形值 public int getIntValue() { return intValue; } // 从整形值构造相应的状态 public static KeeperState fromInt(int intValue) { switch(intValue) { case -1: return KeeperState.Unknown; case 0: return KeeperState.Disconnected; case 1: return KeeperState.NoSyncConnected; case 3: return KeeperState.SyncConnected; case 4: return KeeperState.AuthFailed; case 5: return KeeperState.ConnectedReadOnly; case 6: return KeeperState.SaslAuthenticated; case -112: return KeeperState.Expired; default: throw new RuntimeException("Invalid integer value for conversion to KeeperState"); } } }
