Coverage Report - org.apache.commons.lang3.concurrent.CallableBackgroundInitializer
 
Classes in this File Line Coverage Branch Coverage Complexity
CallableBackgroundInitializer
100%
11/11
100%
2/2
1
 
 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  
 import org.apache.commons.lang3.Validate;
 23  
 
 24  
 /**
 25  
  * <p>
 26  
  * A specialized {@link BackgroundInitializer} implementation that wraps a
 27  
  * {@code Callable} object.
 28  
  * </p>
 29  
  * <p>
 30  
  * An instance of this class is initialized with a {@code Callable} object when
 31  
  * it is constructed. The implementation of the {@link #initialize()} method
 32  
  * defined in the super class delegates to this {@code Callable} so that the
 33  
  * {@code Callable} is executed in the background thread.
 34  
  * </p>
 35  
  * <p>
 36  
  * The {@code java.util.concurrent.Callable} interface is a standard mechanism
 37  
  * of the JDK to define tasks to be executed by another thread. The {@code
 38  
  * CallableBackgroundInitializer} class allows combining this standard interface
 39  
  * with the background initializer API.
 40  
  * </p>
 41  
  * <p>
 42  
  * Usage of this class is very similar to the default usage pattern of the
 43  
  * {@link BackgroundInitializer} class: Just create an instance and provide the
 44  
  * {@code Callable} object to be executed, then call the initializer's
 45  
  * {@link #start()} method. This causes the {@code Callable} to be executed in
 46  
  * another thread. When the results of the {@code Callable} are needed the
 47  
  * initializer's {@link #get()} method can be called (which may block until
 48  
  * background execution is complete). The following code fragment shows a
 49  
  * typical usage example:
 50  
  * </p>
 51  
  *
 52  
  * <pre>
 53  
  * // a Callable that performs a complex computation
 54  
  * Callable&lt;Integer&gt; computationCallable = new MyComputationCallable();
 55  
  * // setup the background initializer
 56  
  * CallableBackgroundInitializer&lt;Integer&gt; initializer =
 57  
  *     new CallableBackgroundInitializer(computationCallable);
 58  
  * initializer.start();
 59  
  * // Now do some other things. Initialization runs in a parallel thread
 60  
  * ...
 61  
  * // Wait for the end of initialization and access the result
 62  
  * Integer result = initializer.get();
 63  
  * </pre>
 64  
  *
 65  
  *
 66  
  * @since 3.0
 67  
  * @param <T> the type of the object managed by this initializer class
 68  
  */
 69  
 public class CallableBackgroundInitializer<T> extends BackgroundInitializer<T> {
 70  
     /** The Callable to be executed. */
 71  
     private final Callable<T> callable;
 72  
 
 73  
     /**
 74  
      * Creates a new instance of {@code CallableBackgroundInitializer} and sets
 75  
      * the {@code Callable} to be executed in a background thread.
 76  
      *
 77  
      * @param call the {@code Callable} (must not be <b>null</b>)
 78  
      * @throws IllegalArgumentException if the {@code Callable} is <b>null</b>
 79  
      */
 80  2
     public CallableBackgroundInitializer(final Callable<T> call) {
 81  2
         checkCallable(call);
 82  1
         callable = call;
 83  1
     }
 84  
 
 85  
     /**
 86  
      * Creates a new instance of {@code CallableBackgroundInitializer} and
 87  
      * initializes it with the {@code Callable} to be executed in a background
 88  
      * thread and the {@code ExecutorService} for managing the background
 89  
      * execution.
 90  
      *
 91  
      * @param call the {@code Callable} (must not be <b>null</b>)
 92  
      * @param exec an external {@code ExecutorService} to be used for task
 93  
      * execution
 94  
      * @throws IllegalArgumentException if the {@code Callable} is <b>null</b>
 95  
      */
 96  
     public CallableBackgroundInitializer(final Callable<T> call, final ExecutorService exec) {
 97  2
         super(exec);
 98  2
         checkCallable(call);
 99  1
         callable = call;
 100  1
     }
 101  
 
 102  
     /**
 103  
      * Performs initialization in a background thread. This implementation
 104  
      * delegates to the {@code Callable} passed at construction time of this
 105  
      * object.
 106  
      *
 107  
      * @return the result of the initialization
 108  
      * @throws Exception if an error occurs
 109  
      */
 110  
     @Override
 111  
     protected T initialize() throws Exception {
 112  1
         return callable.call();
 113  
     }
 114  
 
 115  
     /**
 116  
      * Tests the passed in {@code Callable} and throws an exception if it is
 117  
      * undefined.
 118  
      *
 119  
      * @param call the object to check
 120  
      * @throws IllegalArgumentException if the {@code Callable} is <b>null</b>
 121  
      */
 122  
     private void checkCallable(final Callable<T> call) {
 123  4
         Validate.isTrue(call != null, "Callable must not be null!");
 124  2
     }
 125  
 }