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13   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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25  
26  package com.sun.xml.internal.xsom;
27  
28  import com.sun.xml.internal.xsom.impl.scd.Iterators;
29  import com.sun.xml.internal.xsom.impl.scd.ParseException;
30  import com.sun.xml.internal.xsom.impl.scd.SCDImpl;
31  import com.sun.xml.internal.xsom.impl.scd.SCDParser;
32  import com.sun.xml.internal.xsom.impl.scd.Step;
33  import com.sun.xml.internal.xsom.impl.scd.TokenMgrError;
34  import com.sun.xml.internal.xsom.util.DeferedCollection;
35  
36  import javax.xml.namespace.NamespaceContext;
37  import java.util.Collection;
38  import java.util.Iterator;
39  import java.util.List;
40  
41  /**
42   * Schema Component Designator (SCD).
43   *
44   * <p>
45   * SCD for schema is what XPath is for XML. SCD allows you to select a schema component(s)
46   * from a schema component(s).
47   *
48   * <p>
49   * See <a href="http://www.w3.org/TR/2005/WD-xmlschema-ref-20050329/">XML Schema: Component Designators</a>.
50   * This implementation is based on 03/29/2005 working draft.
51   *
52   * @author Kohsuke Kawaguchi
53   */
54  public abstract class SCD {
55  
56      /**
57       * Parses the string representation of SCD.
58       *
59       * <p>
60       * This method involves parsing the path expression and preparing the in-memory
61       * structure, so this is useful when you plan to use the same SCD against
62       * different context node multiple times.
63       *
64       * <p>
65       * If you want to evaluate SCD just once, use {@link XSComponent#select} methods.
66       *
67       * @param path
68       *      the string representation of SCD, such as "/foo/bar".
69       * @param nsContext
70       *      Its {@link NamespaceContext#getNamespaceURI(String)} is used
71       *      to resolve prefixes in the SCD to the namespace URI.
72       */
73      public static SCD create(String path, NamespaceContext nsContext) throws java.text.ParseException {
74          try {
75              SCDParser p = new SCDParser(path,nsContext);
76              List<?> list = p.RelativeSchemaComponentPath();
77              return new SCDImpl(path,list.toArray(new Step[list.size()]));
78          } catch (TokenMgrError e) {
79              throw setCause(new java.text.ParseException(e.getMessage(), -1 ),e);
80          } catch (ParseException e) {
81              throw setCause(new java.text.ParseException(e.getMessage(), e.currentToken.beginColumn ),e);
82          }
83      }
84  
85      private static java.text.ParseException setCause(java.text.ParseException e, Throwable x) {
86          e.initCause(x);
87          return e;
88      }
89  
90      /**
91       * Evaluates the SCD against the given context node and
92       * returns the matched nodes.
93       *
94       * @return
95       *      could be empty but never be null.
96       */
97      public final Collection<XSComponent> select(XSComponent contextNode) {
98          return new DeferedCollection<XSComponent>(select(Iterators.singleton(contextNode)));
99      }
100 
101     /**
102      * Evaluates the SCD against the whole schema and
103      * returns the matched nodes.
104      *
105      * <p>
106      * This method is here because {@link XSSchemaSet}
107      * doesn't implement {@link XSComponent}.
108      *
109      * @return
110      *      could be empty but never be null.
111      */
112     public final Collection<XSComponent> select(XSSchemaSet contextNode) {
113         return select(contextNode.getSchemas());
114     }
115 
116     /**
117      * Evaluates the SCD against the given context node and
118      * returns the matched node.
119      *
120      * @return
121      *      null if the SCD didn't match anything. If the SCD matched more than one node,
122      *      the first one will be returned.
123      */
124     public final XSComponent selectSingle(XSComponent contextNode) {
125         Iterator<XSComponent> r = select(Iterators.singleton(contextNode));
126         if(r.hasNext())     return r.next();
127         return null;
128     }
129 
130     /**
131      * Evaluates the SCD against the whole schema set and
132      * returns the matched node.
133      *
134      * @return
135      *      null if the SCD didn't match anything. If the SCD matched more than one node,
136      *      the first one will be returned.
137      */
138     public final XSComponent selectSingle(XSSchemaSet contextNode) {
139         Iterator<XSComponent> r = select(contextNode.iterateSchema());
140         if(r.hasNext())     return r.next();
141         return null;
142     }
143 
144     /**
145      * Evaluates the SCD against the given set of context nodes and
146      * returns the matched nodes.
147      *
148      * @param contextNodes
149      *      {@link XSComponent}s that represent the context node against
150      *      which {@link SCD} is evaluated.
151      *
152      * @return
153      *      could be empty but never be null.
154      */
155     public abstract Iterator<XSComponent> select(Iterator<? extends XSComponent> contextNodes);
156 
157     /**
158      * Evaluates the SCD against the given set of context nodes and
159      * returns the matched nodes.
160      *
161      * @param contextNodes
162      *      {@link XSComponent}s that represent the context node against
163      *      which {@link SCD} is evaluated.
164      *
165      * @return
166      *      could be empty but never be null.
167      */
168     public final Collection<XSComponent> select(Collection<? extends XSComponent> contextNodes) {
169         return new DeferedCollection<XSComponent>(select(contextNodes.iterator()));
170     }
171 
172     /**
173      * Returns the textual SCD representation as given to {@link SCD#create(String, NamespaceContext)}.
174      */
175     public abstract String toString();
176 }