XidImpl


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15    * Lesser General Public License for more details.
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21    */
22  package org.jboss.tm;
23  
24  import javax.transaction.xa.Xid  ;
25  
26  /**
27   *  This object encapsulates the ID of a transaction.
28   *  This implementation is immutable and always serializable at runtime.
29   *
30   *  @see TransactionImpl
31   *  @author <a HREF="mailto:rickard.oberg@telkel.com">Rickard ???berg</a>
32   *  @author <a HREF="mailto:osh@sparre.dk">Ole Husgaard</a>
33   *  @author <a HREF="reverbel@ime.usp.br">Francisco Reverbel</a>
34   *  @version $Revision: 37459 $
35   */
36  public class XidImpl
37     implements Xid  , java.io.Serializable  
38  {
39     // Constants -----------------------------------------------------
40  
41     static final long serialVersionUID = -4175838107150528488L;
42  
43     public static final int JBOSS_FORMAT_ID = 0x0101;
44  
45     // Static variable -----------------------------------------------
46  
47     private static boolean trulyGlobalIdsEnabled = false;
48  
49     // Attributes ----------------------------------------------------
50  
51     /**
52      *  Format id of this instance. 
53      *  A JBoss-generated Xids has JBOSS_FORMAT_ID in this field.
54      */
55     private final int formatId;
56  
57     /**
58      *  Global transaction id of this instance.
59      *  The coding of this class depends on the fact that this variable is
60      *  initialized in the constructor and never modified. References to
61      *  this array are never given away, instead a clone is delivered.
62      */
63     private final byte[] globalId;
64  
65     /**
66      *  Branch qualifier of this instance.
67      *  This identifies the branch of a transaction.
68      */
69     private final byte[] branchId;
70  
71     /**
72      *  Hash code of this instance. This is really a sequence number.
73      */
74     private final int hash;
75  
76     /**
77      *  Local id of this instance. This field uniquely identifies a
78      *  transaction within a given JBoss server.
79      */
80     private final long localId;
81  
82     /**
83      *  Global id of this instance. This field uniquely identifies a
84      *  transaction in a distributed environment.
85      */
86     private final GlobalId trulyGlobalId;
87  
88  
89     // Static --------------------------------------------------------
90  
91     /**
92      *  Setter for class variable trulyGlobalIdsEnabled.
93      */
94     public static void setTrulyGlobalIdsEnabled(boolean newValue) 
95     {
96        trulyGlobalIdsEnabled = newValue;
97     }
98  
99     /**
100     *  Getter for class variable trulyGlobalIdsEnabled.
101     */
102    public static boolean getTrulyGlobalIdsEnabled() 
103    {
104       return trulyGlobalIdsEnabled;
105    }
106 
107    /**
108     *  Return a string that describes any Xid instance.
109     */
110    public static String   toString(Xid   id) 
111    {
112       if (id == null)
113          return "[NULL Xid]";
114 
115       String   s = id.getClass().getName();
116       s = s.substring(s.lastIndexOf('.') + 1);
117       s = s + "[FormatId=" + id.getFormatId()
118             + ", GlobalId=" + new String  (id.getGlobalTransactionId()).trim()
119             + ", BranchQual=" + new String  (id.getBranchQualifier()).trim()
120             + ((id instanceof XidImpl) 
121                   ? ", localId=" + LocalId.toString(((XidImpl)id).localId ) 
122                   : "") 
123             + "]";
124 
125       return s;
126    }
127 
128    // Constructors --------------------------------------------------
129 
130    /**
131     *  Create a new instance.
132     */
133    public XidImpl(int formatId, 
134                   byte[] globalId, byte[] branchId, int hash, long localId)
135    {
136       this.formatId = formatId;
137       this.globalId = globalId;
138       this.branchId = branchId;
139       this.hash = hash;
140       this.localId = localId;
141       this.trulyGlobalId = (trulyGlobalIdsEnabled) 
142                            ? new GlobalId(formatId, globalId) 
143                            : null;
144    }
145 
146    /**
147     *  Create a new instance with JBOSS_FORMAT_ID.
148     */
149    XidImpl(byte[] globalId, byte[] branchId, int hash, long localId)
150    {
151       this.formatId = JBOSS_FORMAT_ID;
152       this.globalId = globalId;
153       this.branchId = branchId;
154       this.hash = hash;
155       this.localId = localId;
156       this.trulyGlobalId = (trulyGlobalIdsEnabled) 
157                            ? new GlobalId(JBOSS_FORMAT_ID, globalId, hash)
158                            : null;
159    }
160 
161    /**
162     *  Create a new branch of an existing global transaction ID.
163     *
164     *  @param xidImpl The transaction ID to create a new branch of.
165     *  @param branchId The ID of the new branch.
166     *
167     */
168    public XidImpl(final XidImpl xidImpl, final byte[] branchId)
169    {
170       this.formatId = xidImpl.formatId;
171       this.globalId = xidImpl.globalId; // reuse array, we never modify it
172       this.branchId = branchId;
173       this.hash = xidImpl.hash;
174       this.localId = xidImpl.localId;
175       this.trulyGlobalId = (trulyGlobalIdsEnabled) 
176                            ? xidImpl.trulyGlobalId 
177                            : null;
178    }
179 
180    /**
181     *  Create a new branch of an existing global transaction.
182     *
183     *  @param globalId identifies the transaction to create a new branch of
184     *  @param branchId the id that distiguishes the new branch from other
185     *                  branches of the same transaction
186     *  @param localId  the local id of the transaction 
187     *
188     */
189    public XidImpl(final GlobalId globalId, final byte[] branchId, long localId)
190    {
191       this.formatId = globalId.getFormatId();
192       this.globalId = globalId.getGlobalTransactionId();
193       this.branchId = branchId;
194       this.hash = globalId.hashCode();
195       this.localId = localId;
196       this.trulyGlobalId = (trulyGlobalIdsEnabled) 
197                            ? globalId 
198                            : null;
199    }
200 
201    // Public --------------------------------------------------------
202 
203    // Xid implementation --------------------------------------------
204 
205    /**
206     *  Return the global transaction id of this transaction.
207     */
208    public byte[] getGlobalTransactionId()
209    {
210       return (byte[])globalId.clone();
211    }
212 
213    /**
214     *  Return the branch qualifier of this transaction.
215     */
216    public byte[] getBranchQualifier()
217    {
218       if (branchId.length == 0)
219          return branchId; // Zero length arrays are immutable.
220       else
221          return (byte[])branchId.clone();
222    }
223 
224    /**
225     *  Return the format identifier of this transaction.
226     *
227     *  The format identifier augments the global id and specifies
228     *  how the global id and branch qualifier should be interpreted.
229     */
230    public int getFormatId() 
231    {
232       // The id we return here should be different from all other transaction
233       // implementations.
234       // Known IDs are:
235       // -1:     Sometimes used to denote a null transaction id.
236       // 0:      OSI TP (javadoc states OSI CCR, but that is a bit misleading
237       //         as OSI CCR doesn't even have ACID properties. But OSI CCR and
238       //         OSI TP do have the same id format.)
239       // 1:      Was used by early betas of jBoss.
240       // 0x0101: The JBOSS_FORMAT_ID we use here.
241       // 0xBB14: Used by JONAS.
242       // 0xBB20: Used by JONAS.
243 
244       return formatId;
245    }
246 
247    /**
248     *  Compare for equality.
249     *
250     *  Instances are considered equal if they are both instances of XidImpl,
251     *  and if they have the same format id, the same global transaction id 
252     *  and the same transaction branch qualifier.
253     */
254    public boolean equals(Object   obj)
255    {
256       if(obj==this) 
257          return true;
258       if (obj instanceof XidImpl) {
259          XidImpl other = (XidImpl)obj;
260 
261          if (formatId != other.formatId ||
262              globalId.length != other.globalId.length ||
263              branchId.length != other.branchId.length)
264             return false;
265 
266          for (int i = 0; i < globalId.length; ++i)
267             if (globalId[i] != other.globalId[i])
268                return false;
269 
270          for (int i = 0; i < branchId.length; ++i)
271             if (branchId[i] != other.branchId[i])
272                return false;
273 
274          return true;
275       }
276       return false;
277    }
278 
279    public int hashCode()
280    {
281       return hash;
282    }
283 
284    public String   toString()
285    {
286       return toString(this);
287    }
288 
289    // Methods specific to JBoss Xid implementation ------------------
290 
291    /**
292     *  Return the local id that identifies this transaction 
293     *  within the JBoss server.
294     */
295    public long getLocalIdValue() 
296    {
297       return localId;
298    }
299 
300    /**
301     *  Return a LocalId instance that identifies this transaction 
302     *  within the JBoss server.
303     */
304    public LocalId getLocalId() 
305    {
306       return new LocalId(localId);
307    }
308 
309    /**
310     *  Return a GlobalId instance that identifies this transaction 
311     *  in a distributed environment.
312     */
313    public GlobalId getTrulyGlobalId() 
314    {
315       return trulyGlobalId;
316    }
317 
318    /**
319     *  Compare for same transaction.
320     *
321     *  Instances represent the same transaction if they have the same 
322     *  format id and global transaction id.
323     */
324    public boolean sameTransaction(XidImpl other)
325    {
326       if(other == this) 
327          return true;
328       if (formatId != other.formatId ||
329           globalId.length != other.globalId.length)
330          return false;
331 
332       for (int i = 0; i < globalId.length; ++i)
333          if (globalId[i] != other.globalId[i])
334             return false;
335 
336       return true;
337    }
338 
339    /**
340     *  Return the global transaction id of this transaction.
341     *  Unlike the {@link #getGlobalTransactionId()} method, this one
342     *  returns a reference to the global id byte array that may <em>not</em>
343     *  be changed.
344     */
345    public byte[] getInternalGlobalTransactionId()
346    {
347       return globalId;
348    }
349 
350 }
351 
352
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