Coverage Report - org.apache.commons.lang3.concurrent.CallableBackgroundInitializer
 
Classes in this File Line Coverage Branch Coverage Complexity
CallableBackgroundInitializer
100%
12/12
100%
2/2
1,5
 
 1  
 /*
 2  
  * Licensed to the Apache Software Foundation (ASF) under one or more
 3  
  * contributor license agreements.  See the NOTICE file distributed with
 4  
  * this work for additional information regarding copyright ownership.
 5  
  * The ASF licenses this file to You under the Apache License, Version 2.0
 6  
  * (the "License"); you may not use this file except in compliance with
 7  
  * the License.  You may obtain a copy of the License at
 8  
  *
 9  
  *      http://www.apache.org/licenses/LICENSE-2.0
 10  
  *
 11  
  * Unless required by applicable law or agreed to in writing, software
 12  
  * distributed under the License is distributed on an "AS IS" BASIS,
 13  
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 14  
  * See the License for the specific language governing permissions and
 15  
  * limitations under the License.
 16  
  */
 17  
 package org.apache.commons.lang3.concurrent;
 18  
 
 19  
 import java.util.concurrent.Callable;
 20  
 import java.util.concurrent.ExecutorService;
 21  
 
 22  
 /**
 23  
  * <p>
 24  
  * A specialized {@link BackgroundInitializer} implementation that wraps a
 25  
  * {@code Callable} object.
 26  
  * </p>
 27  
  * <p>
 28  
  * An instance of this class is initialized with a {@code Callable} object when
 29  
  * it is constructed. The implementation of the {@link #initialize()} method
 30  
  * defined in the super class delegates to this {@code Callable} so that the
 31  
  * {@code Callable} is executed in the background thread.
 32  
  * </p>
 33  
  * <p>
 34  
  * The {@code java.util.concurrent.Callable} interface is a standard mechanism
 35  
  * of the JDK to define tasks to be executed by another thread. The {@code
 36  
  * CallableBackgroundInitializer} class allows combining this standard interface
 37  
  * with the background initializer API.
 38  
  * </p>
 39  
  * <p>
 40  
  * Usage of this class is very similar to the default usage pattern of the
 41  
  * {@link BackgroundInitializer} class: Just create an instance and provide the
 42  
  * {@code Callable} object to be executed, then call the initializer's
 43  
  * {@link #start()} method. This causes the {@code Callable} to be executed in
 44  
  * another thread. When the results of the {@code Callable} are needed the
 45  
  * initializer's {@link #get()} method can be called (which may block until
 46  
  * background execution is complete). The following code fragment shows a
 47  
  * typical usage example:
 48  
  * </p>
 49  
  *
 50  
  * <pre>
 51  
  * // a Callable that performs a complex computation
 52  
  * Callable&lt;Integer&gt; computationCallable = new MyComputationCallable();
 53  
  * // setup the background initializer
 54  
  * CallableBackgroundInitializer&lt;Integer&gt; initializer =
 55  
  *     new CallableBackgroundInitializer(computationCallable);
 56  
  * initializer.start();
 57  
  * // Now do some other things. Initialization runs in a parallel thread
 58  
  * ...
 59  
  * // Wait for the end of initialization and access the result
 60  
  * Integer result = initializer.get();
 61  
  * </pre>
 62  
  *
 63  
  *
 64  
  * @since 3.0
 65  
  * @param <T> the type of the object managed by this initializer class
 66  
  */
 67  
 public class CallableBackgroundInitializer<T> extends BackgroundInitializer<T> {
 68  
     /** The Callable to be executed. */
 69  
     private final Callable<T> callable;
 70  
 
 71  
     /**
 72  
      * Creates a new instance of {@code CallableBackgroundInitializer} and sets
 73  
      * the {@code Callable} to be executed in a background thread.
 74  
      *
 75  
      * @param call the {@code Callable} (must not be <b>null</b>)
 76  
      * @throws IllegalArgumentException if the {@code Callable} is <b>null</b>
 77  
      */
 78  2
     public CallableBackgroundInitializer(final Callable<T> call) {
 79  2
         checkCallable(call);
 80  1
         callable = call;
 81  1
     }
 82  
 
 83  
     /**
 84  
      * Creates a new instance of {@code CallableBackgroundInitializer} and
 85  
      * initializes it with the {@code Callable} to be executed in a background
 86  
      * thread and the {@code ExecutorService} for managing the background
 87  
      * execution.
 88  
      *
 89  
      * @param call the {@code Callable} (must not be <b>null</b>)
 90  
      * @param exec an external {@code ExecutorService} to be used for task
 91  
      * execution
 92  
      * @throws IllegalArgumentException if the {@code Callable} is <b>null</b>
 93  
      */
 94  
     public CallableBackgroundInitializer(final Callable<T> call, final ExecutorService exec) {
 95  2
         super(exec);
 96  2
         checkCallable(call);
 97  1
         callable = call;
 98  1
     }
 99  
 
 100  
     /**
 101  
      * Performs initialization in a background thread. This implementation
 102  
      * delegates to the {@code Callable} passed at construction time of this
 103  
      * object.
 104  
      *
 105  
      * @return the result of the initialization
 106  
      * @throws Exception if an error occurs
 107  
      */
 108  
     @Override
 109  
     protected T initialize() throws Exception {
 110  1
         return callable.call();
 111  
     }
 112  
 
 113  
     /**
 114  
      * Tests the passed in {@code Callable} and throws an exception if it is
 115  
      * undefined.
 116  
      *
 117  
      * @param call the object to check
 118  
      * @throws IllegalArgumentException if the {@code Callable} is <b>null</b>
 119  
      */
 120  
     private void checkCallable(final Callable<T> call) {
 121  4
         if (call == null) {
 122  2
             throw new IllegalArgumentException("Callable must not be null!");
 123  
         }
 124  2
     }
 125  
 }