| /* |
| * 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.livy.client.common; |
| |
| import java.util.LinkedList; |
| import java.util.List; |
| import java.util.concurrent.CopyOnWriteArrayList; |
| |
| import org.apache.livy.JobHandle; |
| import org.apache.livy.annotations.Private; |
| |
| @Private |
| public abstract class AbstractJobHandle<T> implements JobHandle<T> { |
| |
| protected final List<Listener<T>> listeners; |
| protected volatile State state; |
| |
| protected AbstractJobHandle() { |
| this.listeners = new LinkedList<>(); |
| this.state = State.SENT; |
| } |
| |
| @Override |
| public State getState() { |
| return state; |
| } |
| |
| @Override |
| public void addListener(Listener<T> l) { |
| synchronized (listeners) { |
| listeners.add(l); |
| fireStateChange(state, l); |
| } |
| } |
| |
| /** |
| * Changes the state of this job handle, making sure that illegal state transitions are ignored. |
| * Fires events appropriately. |
| * |
| * As a rule, state transitions can only occur if the new state is "higher" than the current |
| * state (i.e., has a higher ordinal number) and is not a "final" state. "Final" states are |
| * CANCELLED, FAILED and SUCCEEDED, defined here in the code as having an ordinal number higher |
| * than the CANCELLED enum constant. |
| * |
| * @param newState The new state to change to. |
| * @return Whether the state changed. |
| */ |
| public boolean changeState(State newState) { |
| synchronized (listeners) { |
| if (newState.ordinal() > state.ordinal() && state.ordinal() < State.CANCELLED.ordinal()) { |
| state = newState; |
| for (Listener<T> l : listeners) { |
| fireStateChange(newState, l); |
| } |
| return true; |
| } |
| return false; |
| } |
| } |
| |
| protected abstract T result(); |
| protected abstract Throwable error(); |
| |
| private void fireStateChange(State s, Listener<T> l) { |
| switch (s) { |
| case SENT: |
| break; |
| case QUEUED: |
| l.onJobQueued(this); |
| break; |
| case STARTED: |
| l.onJobStarted(this); |
| break; |
| case CANCELLED: |
| l.onJobCancelled(this); |
| break; |
| case FAILED: |
| l.onJobFailed(this, error()); |
| break; |
| case SUCCEEDED: |
| try { |
| l.onJobSucceeded(this, result()); |
| } catch (Exception e) { |
| // Shouldn't really happen. |
| throw new IllegalStateException(e); |
| } |
| break; |
| default: |
| throw new IllegalStateException(); |
| } |
| } |
| |
| } |