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Java > Open Source Codes > org > apache > avalon > meta > info > DependencyDescriptor


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49 */
50
51 package org.apache.avalon.meta.info;
52
53 import java.util.Properties JavaDoc;
54
55 import org.apache.avalon.framework.Version;
56
57 /**
58  * A descriptor that describes dependency information for
59  * a particular Component. This class contains information
60  * about;
61  * <ul>
62  * <li>role: the name component uses to look up dependency</li>
63  * <li>service: the class/interface that the dependency must provide</li>
64  * </ul>
65  *
66  * <p>Also associated with each dependency is a set of arbitrary
67  * attributes that can be used to store extra information
68  * about dependency. See {@link InfoDescriptor} for example
69  * of how to declare the container specific attributes.</p>
70  *
71  * <p>Possible uses for the attributes are to declare container
72  * specific constraints of component. For example a dependency on
73  * a Corba ORB may also require that the Corba ORB contain the
74  * TimeServer and PersistenceStateService at initialization. Or it
75  * may require that the componenet be multi-thread safe or that
76  * it is persistent etc. These are all container specific
77  * demands.</p>
78  *
79  * @author <a HREF="mailto:dev@avalon.apache.org">Avalon Development Team</a>
80  * @version $Revision: 1.3 $ $Date: 2003/07/12 13:34:27 $
81  */
82 public final class DependencyDescriptor extends Descriptor
83 {
84
85     private static final Version DEFAULT_VERSION = Version.getVersion( "1.0" );
86
87
88     /**
89      * The name the component uses to lookup dependency.
90      */
91     private final String JavaDoc m_key;
92
93     /**
94      * The service class/interface that the dependency must provide.
95      */
96     private final ReferenceDescriptor m_service;
97
98     /**
99      * True if dependency is optional, false otherwise.
100      */
101     private final boolean m_optional;
102
103     /**
104      * Creation of a new dependency descriptor using the default 1.0 version
105      * @param role the role name that will be used by the type when looking up a service
106      * @param service the interface service
107      */
108     public DependencyDescriptor( final String JavaDoc role, String JavaDoc service )
109     {
110         this( role, service, DEFAULT_VERSION );
111     }
112
113     /**
114      * Creation of a new dependency descriptor.
115      * @param role the role name that will be used by the type when looking up a service
116      * @param service the version insterface service reference
117      */
118     public DependencyDescriptor( final String JavaDoc role, String JavaDoc service, Version version )
119     {
120         this( role, new ReferenceDescriptor( service, version ), false, null );
121     }
122
123     /**
124      * Creation of a new dependency descriptor.
125      * @param role the role name that will be used by the type when looking up a service
126      * @param service the version insterface service reference
127      */
128     public DependencyDescriptor( final String JavaDoc role,
129                                  final ReferenceDescriptor service )
130     {
131         this( role, service, false, null );
132     }
133
134     /**
135      * Creation of a new dependency descriptor.
136      * @param role the role name that will be used by the type when looking up a service
137      * @param service the version insterface service reference
138      * @param optional TRUE if this depedency is optional
139      * @param attributes a set of attributes to associate with the dependency
140      */
141     public DependencyDescriptor( final String JavaDoc role,
142                                  final ReferenceDescriptor service,
143                                  final boolean optional,
144                                  final Properties JavaDoc attributes )
145     {
146         super( attributes );
147
148         if ( null == role )
149         {
150             throw new NullPointerException JavaDoc( "role" );
151         }
152
153         if ( null == service )
154         {
155             throw new NullPointerException JavaDoc( "service" );
156         }
157
158         m_key = role;
159         m_service = service;
160         m_optional = optional;
161     }
162
163     /**
164      * Return the name the component uses to lookup the dependency.
165      *
166      * @return the name the component uses to lookup the dependency.
167      */
168     public String JavaDoc getKey()
169     {
170         return m_key;
171     }
172
173     /**
174      * Return the service class/interface descriptor that describes the
175      * dependency that the provider provides.
176      *
177      * @return a reference to service reference that describes the fulfillment
178      * obligations that must be met by a service provider.
179      * @deprecated use getReference()
180      */
181     public ReferenceDescriptor getService()
182     {
183         return m_service;
184     }
185
186     /**
187      * Return the service class/interface descriptor that describes the
188      * dependency must fulfilled by a provider.
189      *
190      * @return a reference to service reference that describes the fulfillment
191      * obligations that must be met by a service provider.
192      */
193     public ReferenceDescriptor getReference()
194     {
195         return m_service;
196     }
197
198     /**
199      * Return true if dependency is optional, false otherwise.
200      *
201      * @return true if dependency is optional, false otherwise.
202      */
203     public boolean isOptional()
204     {
205         return m_optional;
206     }
207
208     /**
209      * Return true if dependency is required, false otherwise.
210      *
211      * @return true if dependency is required, false otherwise.
212      */
213     public boolean isRequired()
214     {
215         return !isOptional();
216     }
217
218     public String JavaDoc toString()
219     {
220         return "[" + getKey() + "] " + getReference();
221     }
222
223     /**
224      * Compare this object with another for equality.
225      * @param other the object to compare this object with
226      * @return TRUE if the supplied object is a reference, service, or service
227      * descriptor that matches this objct in terms of classname and version
228      */
229     public boolean equals( Object JavaDoc other )
230     {
231         boolean isEqual = super.equals( other ) && other instanceof DependencyDescriptor;
232         if ( other instanceof DependencyDescriptor )
233         {
234             DependencyDescriptor dep = (DependencyDescriptor) other;
235
236             isEqual = isEqual && m_optional == dep.m_optional;
237             isEqual = isEqual && m_service.equals( dep.m_service );
238         }
239
240         return isEqual;
241     }
242
243    /**
244     * Return the hashcode for the object.
245     * @return the hashcode value
246     */
247     public int hashCode()
248     {
249         int hash = super.hashCode();
250         hash >>>= 13;
251         hash ^= m_service.hashCode();
252         hash >>>= ( m_optional ) ? 1 : 0;
253
254         return hash;
255     }
256
257 }
258
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