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Java > Open Source Codes > org > exolab > jms > selector > Identifier


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43
44 package org.exolab.jms.selector;
45
46 import javax.jms.DeliveryMode JavaDoc;
47 import javax.jms.JMSException JavaDoc;
48 import javax.jms.Message JavaDoc;
49
50
51 /**
52  * This class implements an identifier. When evaluated, this returns
53  * the value of named header identifier or property, or null if the
54  * identifier is null or the property does not exist.
55  *
56  * @version $Revision: 1.1 $ $Date: 2004/11/26 01:50:44 $
57  * @author <a HREF="mailto:tma@netspace.net.au">Tim Anderson</a>
58  * @see org.exolab.jms.selector.Expression
59  * @see org.exolab.jms.selector.Identifiers
60  */
61 class Identifier implements Expression {
62
63     /**
64      * The identifier name
65      */
66     private final String JavaDoc _name;
67
68     /**
69      * If true the identifier is a header identifier, otherwise it is an user
70      * identifier
71      */
72     private final boolean _headerField;
73
74     /**
75      * Persistent delivery mode
76      */
77     private static final SString PERSISTENT =
78         new SString(Identifiers.PERSISTENT);
79
80     /**
81      * Non-persistent delivery mode
82      */
83     private static final SString NON_PERSISTENT =
84         new SString(Identifiers.NON_PERSISTENT);
85
86
87     /**
88      * Construct a new <code>Identifier</code>
89      *
90      * @param name the identifier name
91      * @throws SelectorException if the identifier cannot be queried by
92      * selectors
93      */
94     public Identifier(final String JavaDoc name) throws SelectorException {
95         _name = name;
96
97         if (Identifiers.isJMSIdentifier(_name)) {
98             if (!Identifiers.isQueryableJMSIdentifier(_name)) {
99                 throw new SelectorException("Invalid header field: " + _name);
100             }
101             _headerField = true;
102         } else {
103             _headerField = false;
104         }
105     }
106
107     /**
108      * Evaluate the expression
109      *
110      * @param msg the message to use to obtain any header identifier and
111      * property values
112      * @return the evaluated result, or <code>null</code> if the value of the
113      * expression is unknown
114      */
115     public final SObject evaluate(final Message JavaDoc msg) {
116         SObject value = null;
117         try {
118             if (_headerField) {
119                 if (_name.equals(Identifiers.JMS_DELIVERY_MODE)) {
120                     value = deliveryMode(msg.getJMSDeliveryMode());
121                 } else if (_name.equals(Identifiers.JMS_PRIORITY)) {
122                     value = new SLong(msg.getJMSPriority());
123                 } else if (_name.equals(Identifiers.JMS_TIMESTAMP)) {
124                     value = new SLong(msg.getJMSTimestamp());
125                 } else if (_name.equals(Identifiers.JMS_MESSAGE_ID)) {
126                     String JavaDoc id = msg.getJMSMessageID();
127                     if (id != null) {
128                         value = new SString(id);
129                     }
130                 } else if (_name.equals(Identifiers.JMS_CORRELATION_ID)) {
131                     String JavaDoc id = msg.getJMSCorrelationID();
132                     if (id != null) {
133                         value = new SString(id);
134                     }
135                 } else if (_name.equals(Identifiers.JMS_TYPE)) {
136                     String JavaDoc type = msg.getJMSType();
137                     if (type != null) {
138                         value = new SString(type);
139                     }
140                 }
141             } else {
142                 value = SObjectFactory.create(msg.getObjectProperty(_name));
143             }
144         } catch (JMSException JavaDoc ignore) {
145             // do nothing
146 }
147         return value;
148     }
149
150     /**
151      * Return a string representation of this expression.
152      *
153      * @return a string representation of this expression
154      */
155     public final String JavaDoc toString() {
156         return _name;
157     }
158
159     /**
160      * Converts the delivery mode to a string
161      *
162      * @param mode the delivery mode. One of
163      * <code>DeliveryMode.PERSISTENT</code> or
164      * <code>DeliveryMode.NON_PERSISTENT</code>
165      * @return the stringified representation of the delivery mode
166      */
167     private SString deliveryMode(final int mode) {
168         SString result = PERSISTENT;
169         if (mode == DeliveryMode.NON_PERSISTENT) {
170             result = NON_PERSISTENT;
171         }
172         return result;
173     }
174
175 }
176
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