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Java > Open Source Codes > com > jcorporate > expresso > kernel > util > DataContextIterator


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64
65 package com.jcorporate.expresso.kernel.util;
66
67 import com.jcorporate.expresso.kernel.DataContext;
68 import com.jcorporate.expresso.kernel.RootContainerInterface;
69 import com.jcorporate.expresso.kernel.management.ExpressoRuntimeMap;
70
71 import java.util.Iterator JavaDoc;
72
73 /**
74  * This class is useful for iterating through all data contexts that are
75  * installed at the root level of the Expresso Runtime hierarchy. Use it
76  * like a normal iterator except that it is explictly constructed.
77  * <p>Example Usage:<br/>
78  * <code>
79  * &nbsp;&nbsp;for (DataContextIterator it = new DataContextIterator();
80  * it.hasNext();) {<br/>
81  * &nbsp;&nbsp;&nbsp;&nbsp; DataContext oneContext = (DataContext)it.next();<br />
82  * &nbsp;&nbsp;&nbsp;&nbsp; System.out.println("Context Name: " + oneContext.getMetaData().getName());<br />
83  * &nbsp;&nbsp;}<br />
84  * </code>
85  * </p>
86  *
87  * @author Michael Rimov
88  * @version $Revision: 1.6 $ on $Date: 2004/11/17 20:48:17 $
89  * @since Expresso 5.1
90  */
91 public class DataContextIterator implements Iterator JavaDoc {
92     RootContainerInterface runtime;
93     Iterator JavaDoc currentChild;
94     DataContext next = null;
95
96     /**
97      * Default constructor. Searches for and gets the default runtime map.
98      *
99      * @throws IllegalArgumentException if the iterator is unable to find the
100      * runtime.
101      */
102     public DataContextIterator() {
103         runtime = ExpressoRuntimeMap.getDefaultRuntime();
104
105         if (runtime == null) {
106             throw new IllegalArgumentException JavaDoc("No default runtime installed");
107         }
108         currentChild = runtime.getContainerImplementation()
109                 .getChildComponents().values().iterator();
110         findNext();
111     }
112
113     /**
114      * Constructor that finds a runtime by name.
115      *
116      * @param runtimeName The name of the runtime the user wants to iterate
117      * @throws IllegalArgumentException if the iterator is unable to find the
118      * runtime.
119      */
120     public DataContextIterator(String JavaDoc runtimeName) {
121         runtime = ExpressoRuntimeMap.getRuntime(runtimeName);
122         if (runtime == null) {
123             throw new IllegalArgumentException JavaDoc("No runtime by the name: "
124                     + runtimeName + " installed!");
125         }
126
127         currentChild = runtime.getContainerImplementation()
128                 .getChildComponents().values().iterator();
129         findNext();
130     }
131
132     /**
133      * Constructor that uses the RootContainerInterface given to it.
134      *
135      * @param iteratingRuntime the RootContainerInterface to iterate.
136      */
137     public DataContextIterator(RootContainerInterface iteratingRuntime) {
138         runtime = iteratingRuntime;
139         if (runtime == null) {
140             throw new IllegalArgumentException JavaDoc("Parameter iteratingRuntime cannot be null.");
141         }
142
143         currentChild = runtime.getContainerImplementation()
144                 .getChildComponents().values().iterator();
145         findNext();
146     }
147
148     /**
149      * Checks if another object exists.
150      *
151      * @return true if there is another data context to iterate.
152      * @see java.util.Iterator#hasNext
153      */
154     public boolean hasNext() {
155         return (next != null) ? true : false;
156     }
157
158     /**
159      * Retrieve the Next Data Context in the sequence.
160      *
161      * @return an Object that is of type com.jcorporate.expresso.kernel.DataContext
162      * @throws ArrayIndexOutOfBoundsException if we iterate past the end.
163      */
164     public Object JavaDoc next() {
165         if (next == null) {
166             throw new java.lang.ArrayIndexOutOfBoundsException JavaDoc("No more contexts");
167         }
168         Object JavaDoc returnValue = next;
169         findNext();
170         return returnValue;
171     }
172
173     /**
174      * Retrieve the Next Data Context in the sequence. The only difference between
175      * this and next() is that this function doesn't require a downcast.
176      *
177      * @return an Object that is of type com.jcorporate.expresso.kernel.DataContext
178      * @throws ArrayIndexOutOfBoundsException if we iterate past the end.
179      */
180     public DataContext nextContext() {
181         if (next == null) {
182             throw new java.lang.ArrayIndexOutOfBoundsException JavaDoc("No more contexts");
183         }
184         DataContext returnValue = next;
185         findNext();
186         return returnValue;
187     }
188
189
190     /**
191      * Not implemented. Way too dangerous of a capability
192      */
193     public void remove() {
194         throw new java.lang.UnsupportedOperationException JavaDoc("Method remove() not yet implemented.");
195     }
196
197     /**
198      * Find and load the next values
199      */
200     private void findNext() {
201         next = null;
202         while (currentChild.hasNext()) {
203             Object JavaDoc oneObj = currentChild.next();
204             if (oneObj instanceof DataContext) {
205                 next = (DataContext) oneObj;
206                 break;
207             }
208         }
209
210     }
211 }
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