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         protected AbstractComponent(String aName) {
  63                 this(aName, new ProvidedInterface[0], new RequiredInterface[0]);
  64         }
  65
  66         public AbstractComponent addProvidedInterface(ProvidedInterface aProvided) {
  67                 _provided.add(aProvided);
  68                 return this;
  69         }
  70
  71         public AbstractComponent addRequiredInterface(RequiredInterface aRequired) {
  72                 _required.add(aRequired);
  73                 return this;
  74         }
  75
  76         @Override
  77         public final String getName() {
  78                 return _name;
  79         }
  80
  81         @Override
  82         public void addContext(String aContext) {
  83                 if (_context == null) {
  84                         _context = aContext;
  85                 } else {
  86                         _context = aContext + "." + _context;
  87                 }
  88         }
  89
  90         @Override
  91         public String getContext() {
  92                 return _context;
  93         }
  94
  95         @Override
  96         public String getQualifiedName() {
  97                 if (_context == null) {
  98                         return getName();
  99                 }
 100                 return _context + "." + getName();
 101         }
 102
 103         @Override
 104         public final ProvidedInterface[] getProvidedInterfaces() {
 105                 return _provided.toArray(new ProvidedInterface[0]);
 106         }
 107
 108         @Override
 109         public final RequiredInterface[] getRequiredInterfaces() {
 110                 return _required.toArray(new RequiredInterface[0]);
 111         }
 112
 113         @Override
 114         public final Type start(Scope aScope) {
 115                 LOG.info("Initialization starting '" + getQualifiedName() + "'");
 116                 List<ProvidedInterface> oldRemaining = _remaining.get();
 117                 _remaining.set(new ArrayList<ProvidedInterface>(Arrays.asList(getProvidedInterfaces())));
 118                 try {
 119                         Type runtime = doStart(aScope);
 120                         checkNotStartedInterfaces();
 121                         LOG.info("Initialization finished '" + getQualifiedName() + "'");
 122                         return runtime;
 123                 } finally {
 124                         _remaining.set(oldRemaining);
 125                 }
 126         }
 127
 128         private void checkNotStartedInterfaces() {
 129                 if (_remaining.get().size() > 0) {
 130                         String notProvided = "";
 131                         for (ProvidedInterface provided : _remaining.get()) {
 132                                 notProvided += "\nComponent " + getQualifiedName()
 133                                                 + " did not start interface " + provided;
 134                         }
 135                         throw new SystemAssemblyException(notProvided);
 136                 }
 137         }
 138
 139         /**
 140          * Must be implemented for initializing the subsystem. The implementation
 141          * must call {@link #addService(Service)} for each service that is started.
 142          *
 143          * @return Returns the runtime of the component.
 144          */
 145         protected abstract Type doStart(Scope aScope);
 146
 147         /**
 148          * Implementations must call this method to indicate that a new service has
 149          * been started.
 150          *
 151          * @param aDescriptor
 152          *            Provided interface.
 153          * @param aService
 154          *            Implementation of the interface.
 155          * @param aScope
 156          *            scope in which to publish the implementation.
 157          */
 158         protected final void addInterface(ProvidedInterface aDescriptor,
 159                         Object aService, Scope aScope) {
 160                 LOG.info("Interface '" + getQualifiedName() + "."
 161                                 + aDescriptor.getName() + "' started.");
 162                 if ( !_remaining.get().remove(aDescriptor) ) {
 163                     throw new SystemAssemblyException("Component '" + getQualifiedName() + "' started an unexpected interface '" +
 164                             aDescriptor + "' that was not registerd as a provided interface before");
 165                 }
 166                 aScope.publishInterface(aDescriptor, aService);
 167         }
 168
 169         @Override
 170         public void stop(Type aRuntime) {
 171             LOG.info("Stopping initiated '" + getQualifiedName() + "'");
 172                 doStop(aRuntime);
 173                 LOG.info("Stopping completed '" + getQualifiedName() + "'");
 174         }
 175
 176         protected abstract void doStop(Type aRuntime);
 177
 178         @Override
 179         public String toString() {
 180                 return getQualifiedName();
 181         }
 182
 183 }