001 package edu.nrao.sss.html;
002
003 import javax.swing.text.html.HTML;
004
005 /**
006 * An attribute (see {@link javax.swing.text.html.HTML.Attribute})
007 * of an HTML element.
008 * <p>
009 * <b>Version Info:</b>
010 * <table style="margin-left:2em">
011 * <tr><td>$Revision: 545 $</td></tr>
012 * <tr><td>$Date: 2007-04-19 10:38:45 -0600 (Thu, 19 Apr 2007) $</td></tr>
013 * <tr><td>$Author: dharland $</td></tr>
014 * </table></p>
015 *
016 * @author David M. Harland
017 * @since 2007-03-15
018 */
019 public class HtmlAttribute
020 {
021 private HTML.Attribute type; //Not mutable after construction
022 private String value;
023
024 /**
025 * Creates a new HTML attribute of the given type and value.
026 *
027 * @param attrName the name, or type, of this attribute.
028 * This value must be a valid attribute name.
029 * Validity is determined by
030 * {@link HTML#getAttributeKey(String)}.
031 * A list of known attribute names may be found in
032 * {@link javax.swing.text.html.HTML.Attribute}.</p>
033 *
034 * @param attrValue the value of this attribute.
035 * See {@link #setValue(String)} for the rules about this
036 * parameter.
037 */
038 public HtmlAttribute(String attrName, String attrValue)
039 {
040 //Use name to get a valid attribute
041 type = HTML.getAttributeKey(attrName);
042
043 if (type == null)
044 throw new IllegalArgumentException("Attribute name [" + attrName +
045 "] is not recognized as a valid name.");
046 setValue(attrValue);
047 }
048
049 /**
050 * Creates a new HTML attribute of the given type and value.
051 *
052 * @param attrType the type of this attribute. If this parameter is
053 * <i>null</i> an {@code IllegalArgumentException}
054 * will be thrown.
055 *
056 * @param attrValue the value of this attribute.
057 * See {@link #setValue(String)} for the rules about this
058 * parameter.
059 */
060 public HtmlAttribute(HTML.Attribute attrType, String attrValue)
061 {
062 if (attrType == null)
063 throw new IllegalArgumentException("May not have null attribute type.");
064
065 type = attrType;
066 setValue(attrValue);
067 }
068
069 /**
070 * Creates a new HTML attribute of the given type and with a value of
071 * the empty string (<tt>""</tt>).
072 *
073 * @param attrType the type of this attribute. If this parameter is
074 * <i>null</i> an {@code IllegalArgumentException}
075 * will be thrown.
076 */
077 public HtmlAttribute(HTML.Attribute attrType)
078 {
079 this(attrType, "");
080 }
081
082 /**
083 * Returns the type of this attribute.
084 * @return the type of this attribute. This value is guaranteeed to be
085 * non-null.
086 */
087 public HTML.Attribute getType()
088 {
089 return type;
090 }
091
092 /**
093 * Sets the value of this attribute.
094 *
095 * @param newValue a new value for this attribute. If this parameter is
096 * <i>null</i>, it will be replaced by the empty
097 * string (<tt>""</tt>). This parameter may contain
098 * single quote (<tt>'</tt>) or double quote
099 * (<tt>"</tt>) characters, but not both. If it does,
100 * an {@code IllegalArgumentException} will be thrown
101 * and this attribute's value will be left in its
102 * present state.
103 */
104 public final void setValue(String newValue)
105 {
106 if (newValue == null)
107 newValue = "";
108
109 if (newValue.contains("'") && newValue.contains("\""))
110 throw new IllegalArgumentException(
111 "newValue [" + newValue +
112 "] may not have both single and double quotes.");
113
114 value = newValue;
115 }
116
117 /**
118 * Returns the value of this attribute.
119 *
120 * @return the value of this attribute. This value is guaranteeed to be
121 * non-null, but could be an empty string (<tt>""</tt>).
122 */
123 public String getValue()
124 {
125 return value;
126 }
127
128 /**
129 * Creates and returns a new HTML attribute by parsing {@code nameValueText}.
130 *
131 * @param nameValueText the HTML form of this attribute.
132 * The expected form of the text is:
133 * <pre> name="value"</pre>
134 * Values may be quoted with either single (') or double (") quotes.
135 * Leading and trailing whitespace is permitted and will be trimmed during
136 * parsing.
137 * The <tt>name</tt> must be a valid attribute name. Validity is determined
138 * by {@link HTML#getAttributeKey(String)}. A list of known attribute names
139 * may be found in {@link javax.swing.text.html.HTML.Attribute}.</p>
140 *
141 * @return a new HTML attribute by parsing {@code nameValueText}.
142 *
143 * @throws IllegalArgumentException if anything goes wrong during parsing.
144 */
145 public static HtmlAttribute parse(String nameValueText)
146 {
147 StringBuilder nameValueBuff = new StringBuilder(nameValueText.trim());
148 StringBuilder tempBuff = new StringBuilder();
149 int charCount = nameValueBuff.length();
150
151 String name, value;
152
153 //Ensure we have format name="value"
154 try
155 {
156 //Look for the name
157 int c = 0;
158 char ch = nameValueBuff.charAt(c);
159 while (ch != '=')
160 {
161 tempBuff.append(ch);
162 ch = nameValueBuff.charAt(++c);
163 }
164
165 name = tempBuff.toString().trim().toLowerCase();
166
167 //Skip any white space after '='
168 c++;
169 while (Character.isWhitespace(nameValueBuff.charAt(c)))
170 c++;
171
172 //Look for the value
173 tempBuff.delete(0, tempBuff.length());
174 char quoteChar = nameValueBuff.charAt(c); //Could be " or '
175 ch = nameValueBuff.charAt(++c);
176 while (ch != quoteChar)
177 {
178 tempBuff.append(ch);
179 ch = nameValueBuff.charAt(++c);
180 }
181
182 if (++c < charCount)
183 throw new IllegalArgumentException(
184 "Extra characters found beyond value's closing quote.");
185
186 value = tempBuff.toString();
187 }
188 catch (Exception ex)
189 {
190 throw new IllegalArgumentException("Could not parse nameValueText [" +
191 nameValueText + "]: " +
192 ex.getMessage());
193 }
194
195 //Use name to get a valid attribute
196 HTML.Attribute attrType = HTML.getAttributeKey(name);
197
198 if (attrType == null)
199 throw new IllegalArgumentException("Attribute name [" + name +
200 "] in nameValueText [" + nameValueText+
201 "] is not recognized as a valid name.");
202
203 return new HtmlAttribute(attrType, value);
204 }
205
206 /**
207 * Returns a string of the form <tt>name="value"</tt>.
208 * If <i>value</i> itself contains double-quote characters,
209 * the returned string will be of the form <tt>name='value'</tt>.
210 */
211 @Override
212 public String toString()
213 {
214 char quoteChar = value.contains("\"") ? '\'' : '"';
215
216 StringBuilder buff = new StringBuilder(type.toString());
217
218 buff.append('=').append(quoteChar).append(value).append(quoteChar);
219
220 return buff.toString();
221 }
222
223 /** Returns <i>true</i> if {@code o} is equal to this attribute. */
224 @Override
225 public boolean equals(Object o)
226 {
227 //Quick exit if o is this
228 if (o == this)
229 return true;
230
231 //Quick exit if o is null
232 if (o == null)
233 return false;
234
235 //Quick exit if classes are different
236 if (!o.getClass().equals(this.getClass()))
237 return false;
238
239 HtmlAttribute other = (HtmlAttribute)o;
240
241 return this.type.equals(other.type) &&
242 this.value.equals(other.value);
243 }
244
245 @Override
246 /** Returns a hash code value for this cell. */
247 public int hashCode()
248 {
249 //Taken from the Effective Java book by Joshua Bloch.
250 //The constants 17 & 37 are arbitrary & carry no meaning.
251 int result = 17;
252
253 //You MUST keep this method in synch w/ equals
254
255 result = 37 * result + type.hashCode();
256 result = 37 * result + value.hashCode();
257
258 return result;
259 }
260 /*
261 public static void main(String[] args)
262 {
263 HtmlAttribute attr = HtmlAttribute.parse(" name ='Richard \"Dick\" Cheney' ");
264 System.out.println(attr);
265
266 attr = HtmlAttribute.parse(attr.toString());
267 System.out.println(attr);
268
269 attr = HtmlAttribute.parse("name='Barney' class=\"72\" color='pale'");
270 System.out.println(attr);
271
272 //attr = HtmlAttribute.parse("name='Fred Flintstone\"");
273 //System.out.println(attr);
274
275 //attr = HtmlAttribute.parse("fruit=\"Apple\"");
276 //System.out.println(attr);
277 }
278 */
279 }