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Java > Open Source Codes > org > apache > commons > beanutils > converters > AbstractArrayConverter


1 /*
2  * Copyright 2001-2004 The Apache Software Foundation.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16
17
18 package org.apache.commons.beanutils.converters;
19
20
21 import java.io.IOException JavaDoc;
22 import java.io.StreamTokenizer JavaDoc;
23 import java.io.StringReader JavaDoc;
24 import java.util.ArrayList JavaDoc;
25 import java.util.List JavaDoc;
26 import org.apache.commons.beanutils.ConversionException;
27 import org.apache.commons.beanutils.Converter;
28
29
30
31 /**
32  * <p>Convenience base class for converters that translate the String
33  * representation of an array into a corresponding array of primitives
34  * object. This class encapsulates the functionality required to parse
35  * the String into a list of String elements that can later be
36  * individually converted to the appropriate primitive type.</p>
37  *
38  * <p>The input syntax accepted by the <code>parseElements()</code> method
39  * is designed to be compatible with the syntax used to initialize arrays
40  * in a Java source program, except that only String literal values are
41  * supported. For maximum flexibility, the surrounding '{' and '}'
42  * characters are optional, and individual elements may be separated by
43  * any combination of whitespace and comma characters.</p>
44  *
45  * @author Craig R. McClanahan
46  * @version $Revision: 1.6 $ $Date: 2004/02/28 13:18:34 $
47  * @since 1.4
48  */
49
50 public abstract class AbstractArrayConverter implements Converter {
51
52
53     // ----------------------------------------------------- Instance Variables
54
55
56     /**
57      * The default value specified to our Constructor, if any.
58      */
59     protected Object JavaDoc defaultValue = null;
60
61
62     /**
63      * <p>Model object for string arrays.</p>
64      */
65     protected static String JavaDoc strings[] = new String JavaDoc[0];
66
67
68     /**
69      * Should we return the default value on conversion errors?
70      */
71     protected boolean useDefault = true;
72
73
74     // --------------------------------------------------------- Public Methods
75
76
77     /**
78      * Convert the specified input object into an output object of the
79      * specified type. This method must be implemented by a concrete
80      * subclass.
81      *
82      * @param type Data type to which this value should be converted
83      * @param value The input value to be converted
84      *
85      * @exception ConversionException if conversion cannot be performed
86      * successfully
87      */
88     public abstract Object JavaDoc convert(Class JavaDoc type, Object JavaDoc value);
89
90
91     // ------------------------------------------------------ Protected Methods
92
93
94     /**
95      * <p>Parse an incoming String of the form similar to an array initializer
96      * in the Java language into a <code>List</code> individual Strings
97      * for each element, according to the following rules.</p>
98      * <ul>
99      * <li>The string must have matching '{' and '}' delimiters around
100      * a comma-delimited list of values.</li>
101      * <li>Whitespace before and after each element is stripped.
102      * <li>If an element is itself delimited by matching single or double
103      * quotes, the usual rules for interpreting a quoted String apply.</li>
104      * </ul>
105      *
106      * @param svalue String value to be parsed
107      *
108      * @exception ConversionException if the syntax of <code>svalue</code>
109      * is not syntactically valid
110      * @exception NullPointerException if <code>svalue</code>
111      * is <code>null</code>
112      */
113     protected List JavaDoc parseElements(String JavaDoc svalue) {
114
115         // Validate the passed argument
116 if (svalue == null) {
117             throw new NullPointerException JavaDoc();
118         }
119
120         // Trim any matching '{' and '}' delimiters
121 svalue = svalue.trim();
122         if (svalue.startsWith("{") && svalue.endsWith("}")) {
123             svalue = svalue.substring(1, svalue.length() - 1);
124         }
125
126         try {
127
128             // Set up a StreamTokenizer on the characters in this String
129 StreamTokenizer JavaDoc st =
130                 new StreamTokenizer JavaDoc(new StringReader JavaDoc(svalue));
131             st.whitespaceChars(',',','); // Commas are delimiters
132 st.ordinaryChars('0', '9'); // Needed to turn off numeric flag
133 st.ordinaryChars('.', '.');
134             st.ordinaryChars('-', '-');
135             st.wordChars('0', '9'); // Needed to make part of tokens
136 st.wordChars('.', '.');
137             st.wordChars('-', '-');
138
139             // Split comma-delimited tokens into a List
140 ArrayList JavaDoc list = new ArrayList JavaDoc();
141             while (true) {
142                 int ttype = st.nextToken();
143                 if ((ttype == StreamTokenizer.TT_WORD) ||
144                     (ttype > 0)) {
145                     list.add(st.sval);
146                 } else if (ttype == StreamTokenizer.TT_EOF) {
147                     break;
148                 } else {
149                     throw new ConversionException
150                         ("Encountered token of type " + ttype);
151                 }
152             }
153
154             // Return the completed list
155 return (list);
156
157         } catch (IOException JavaDoc e) {
158
159             throw new ConversionException(e);
160
161         }
162
163
164
165     }
166
167
168 }
169
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