1 /*
2 * $Header: /home/cvs/jakarta-commons-sandbox/jelly/src/java/org/apache/commons/jelly/tags/core/ForEachTag.java,v 1.15 2002/06/26 14:50:43 jstrachan Exp $
3 * $Revision: 1.15 $
4 * $Date: 2002/06/26 14:50:43 $
5 *
6 * ====================================================================
7 *
8 * The Apache Software License, Version 1.1
9 *
10 * Copyright (c) 1999-2002 The Apache Software Foundation. All rights
11 * reserved.
12 *
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
15 * are met:
16 *
17 * 1. Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 *
20 * 2. Redistributions in binary form must reproduce the above copyright
21 * notice, this list of conditions and the following disclaimer in
22 * the documentation and/or other materials provided with the
23 * distribution.
24 *
25 * 3. The end-user documentation included with the redistribution, if
26 * any, must include the following acknowlegement:
27 * "This product includes software developed by the
28 * Apache Software Foundation (http://www.apache.org/)."
29 * Alternately, this acknowlegement may appear in the software itself,
30 * if and wherever such third-party acknowlegements normally appear.
31 *
32 * 4. The names "The Jakarta Project", "Commons", and "Apache Software
33 * Foundation" must not be used to endorse or promote products derived
34 * from this software without prior written permission. For written
35 * permission, please contact apache@apache.org.
36 *
37 * 5. Products derived from this software may not be called "Apache"
38 * nor may "Apache" appear in their names without prior written
39 * permission of the Apache Group.
40 *
41 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
42 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
43 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
44 * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
45 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
46 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
47 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
48 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
49 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
50 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
51 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
52 * SUCH DAMAGE.
53 * ====================================================================
54 *
55 * This software consists of voluntary contributions made by many
56 * individuals on behalf of the Apache Software Foundation. For more
57 * information on the Apache Software Foundation, please see
58 * <http://www.apache.org/>.
59 *
60 * $Id: ForEachTag.java,v 1.15 2002/06/26 14:50:43 jstrachan Exp $
61 */
62
63 package org.apache.commons.jelly.tags.core;
64
65 import java.io.IOException;
66 import java.io.Writer;
67 import java.util.Iterator;
68 import java.util.List;
69
70 import org.apache.commons.jelly.JellyContext;
71 import org.apache.commons.jelly.MissingAttributeException;
72 import org.apache.commons.jelly.Script;
73 import org.apache.commons.jelly.TagSupport;
74 import org.apache.commons.jelly.XMLOutput;
75 import org.apache.commons.jelly.expression.Expression;
76
77 import org.apache.commons.logging.Log;
78 import org.apache.commons.logging.LogFactory;
79
80 /*** A tag which performs an iteration over the results of an XPath expression
81 *
82 * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
83 * @version $Revision: 1.15 $
84 */
85 public class ForEachTag extends TagSupport {
86
87 /*** The Log to which logging calls will be made. */
88 private static final Log log = LogFactory.getLog(ForEachTag.class);
89
90 /*** Holds the variable name to export for the item being iterated over. */
91 private Expression items;
92
93 /***
94 * If specified then the current item iterated through will be defined
95 * as the given variable name.
96 */
97 private String var;
98
99 /***
100 * If specified then the current index counter will be defined
101 * as the given variable name.
102 */
103 private String indexVar;
104
105 /*** The starting index value */
106 private int begin;
107
108 /*** The ending index value */
109 private int end = Integer.MAX_VALUE;
110
111 /*** The index increment step */
112 private int step = 1;
113
114 /*** The iteration index */
115 private int index;
116
117 public ForEachTag() {
118 }
119
120 // Tag interface
121
122 //-------------------------------------------------------------------------
123 public void doTag(XMLOutput output) throws Exception {
124
125 if (log.isDebugEnabled()) {
126 log.debug("running with items: " + items);
127 }
128
129 if (items != null) {
130 Iterator iter = items.evaluateAsIterator(context);
131 if (log.isDebugEnabled()) {
132 log.debug("Iterating through: " + iter);
133 }
134
135 // ignore the first items of the iterator
136 for (index = 0; index < begin && iter.hasNext(); index++ ) {
137 iter.next();
138 }
139
140 while (iter.hasNext() && index < end) {
141 Object value = iter.next();
142 if (var != null) {
143 context.setVariable(var, value);
144 }
145 if (indexVar != null) {
146 context.setVariable(indexVar, new Integer(index));
147 }
148 invokeBody(output);
149
150 // now we need to move to next index
151 index++;
152 for ( int i = 1; i < step; i++, index++ ) {
153 if ( ! iter.hasNext() ) {
154 return;
155 }
156 iter.next();
157 }
158 }
159 }
160 else {
161 if ( end == Integer.MAX_VALUE && begin == 0 ) {
162 throw new MissingAttributeException( "items" );
163 }
164 else {
165 String varName = var;
166 if ( varName == null ) {
167 varName = indexVar;
168 }
169
170 for (index = begin; index < end; index += step ) {
171
172 if (varName != null) {
173 Object value = new Integer(index);
174 context.setVariable(varName, value);
175 }
176 invokeBody(output);
177 }
178 }
179 }
180 }
181
182 // Properties
183 //-------------------------------------------------------------------------
184
185 /*** Sets the expression used to iterate over
186 */
187 public void setItems(Expression items) {
188 this.items = items;
189 }
190
191 /*** Sets the variable name to export for the item being iterated over
192 */
193 public void setVar(String var) {
194 this.var = var;
195 }
196
197 /*** Sets the variable name to export the current index counter to
198 */
199 public void setIndexVar(String indexVar) {
200 this.indexVar = indexVar;
201 }
202
203 /*** Sets the starting index value
204 */
205 public void setBegin(int begin) {
206 this.begin = begin;
207 }
208
209 /*** Sets the ending index value
210 */
211 public void setEnd(int end) {
212 this.end = end;
213 }
214
215 /*** Sets the index increment step
216 */
217 public void setStep(int step) {
218 this.step = step;
219 }
220 }
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