wamblee.org Git - utils/blob - system/general/src/main/java/org/wamblee/system/core/AbstractComponent.java

   1 /*
   2  * Copyright 2007 the original author or authors.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *      http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16 package org.wamblee.system.core;
  17
  18 import java.util.ArrayList;
  19 import java.util.Arrays;
  20 import java.util.HashSet;
  21 import java.util.List;
  22 import java.util.Set;
  23
  24 import org.apache.commons.logging.Log;
  25 import org.apache.commons.logging.LogFactory;
  26
  27 /**
  28  * Abstract subsystem class making it easy to implement new subsystems.
  29  */
  30 public abstract class AbstractComponent<Type> implements Component<Type> {
  31
  32         private static final Log LOG = LogFactory.getLog(AbstractComponent.class);
  33
  34         private ThreadLocal<List<ProvidedInterface>> _remaining;
  35
  36         private String _context;
  37         private String _name;
  38         private List<ProvidedInterface> _provided;
  39         private List<RequiredInterface> _required;
  40
  41         /**
  42          * Constructs the subsystem.
  43          *
  44          * @param aName
  45          *            Name of the system.
  46          * @param aProvided
  47          *            Provided services.
  48          * @param aRequired
  49          *            Required services.
  50          */
  51         protected AbstractComponent(String aName, ProvidedInterface[] aProvided,
  52                         RequiredInterface[] aRequired) {
  53                 _remaining = new ThreadLocal<List<ProvidedInterface>>();
  54                 _context = null;
  55                 _name = aName;
  56                 _provided = new ArrayList<ProvidedInterface>();
  57                 _provided.addAll(Arrays.asList(aProvided));
  58                 _required = new ArrayList<RequiredInterface>();
  59                 _required.addAll(Arrays.asList(aRequired));
  60         }
  61
  62         @Override
  63         public final String getName() {
  64                 return _name;
  65         }
  66
  67         @Override
  68         public void addContext(String aContext) {
  69                 if (_context == null) {
  70                         _context = aContext;
  71                 } else {
  72                         _context = aContext + "." + _context;
  73                 }
  74         }
  75
  76         @Override
  77         public String getQualifiedName() {
  78                 if (_context == null) {
  79                         return getName();
  80                 }
  81                 return _context + "." + getName();
  82         }
  83
  84         @Override
  85         public final ProvidedInterface[] getProvidedInterfaces() {
  86                 return _provided.toArray(new ProvidedInterface[0]);
  87         }
  88
  89         @Override
  90         public final RequiredInterface[] getRequiredInterfaces() {
  91                 return _required.toArray(new RequiredInterface[0]);
  92         }
  93
  94         @Override
  95         public final Type start(Scope aScope) {
  96                 LOG.info("Initializing '" + getQualifiedName() + "'");
  97                 List<ProvidedInterface> oldRemaining = _remaining.get();
  98                 _remaining.set(new ArrayList<ProvidedInterface>(Arrays.asList(getProvidedInterfaces())));
  99                 try {
 100                         Type runtime = doStart(aScope);
 101                         checkNotStartedInterfaces();
 102                         return runtime;
 103                 } finally {
 104                         _remaining.set(oldRemaining);
 105                 }
 106         }
 107
 108         private void checkNotStartedInterfaces() {
 109                 if (_remaining.get().size() > 0) {
 110                         String notProvided = "";
 111                         for (ProvidedInterface provided : _remaining.get()) {
 112                                 notProvided += "\nComponent " + getQualifiedName()
 113                                                 + " did not start interface " + provided;
 114                         }
 115                         throw new SystemAssemblyException(notProvided);
 116                 }
 117         }
 118
 119         /**
 120          * Must be implemented for initializing the subsystem. The implementation
 121          * must call {@link #addService(Service)} for each service that is started.
 122          *
 123          * @return Returns the runtime of the component.
 124          */
 125         protected abstract Type doStart(Scope aScope);
 126
 127         /**
 128          * Implementations must call this method to indicate that a new service has
 129          * been started.
 130          *
 131          * @param aDescriptor
 132          *            Provided interface.
 133          * @param aService
 134          *            Implementation of the interface.
 135          * @param aScope
 136          *            scope in which to publish the implementation.
 137          */
 138         protected final void addInterface(ProvidedInterface aDescriptor,
 139                         Object aService, Scope aScope) {
 140                 LOG.info("Interface '" + getQualifiedName() + "."
 141                                 + aDescriptor.getName() + "' started.");
 142                 _remaining.get().remove(aDescriptor);
 143                 aScope.publishInterface(aDescriptor, aService);
 144         }
 145
 146         @Override
 147         public void stop(Type aRuntime) {
 148                 doStop(aRuntime);
 149         }
 150
 151         protected abstract void doStop(Type aRuntime);
 152
 153         @Override
 154         public String toString() {
 155                 return getQualifiedName();
 156         }
 157
 158 }