Element


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23  package org.infoglue.cms.workflow.taglib;
24  
25  import java.text.MessageFormat  ;
26  import java.util.ArrayList  ;
27  import java.util.HashMap  ;
28  import java.util.Iterator  ;
29  import java.util.List  ;
30  import java.util.Map  ;
31  
32  /**
33   * Utility class for creating html elements.
34   * Most functions returns the element itself to allow chained operations.
35   */
36  class Element 
37  {
38      /**
39       * Pattern for an attribute.
40       */
41      private static final String   ATTRIBUTE = "{0}=\"{1}\"";
42      
43      /**
44       * Pattern for an element with both attributes and children.
45       */
46      private static final String   CHILDREN_AND_ATTRIBUTES = "<{0} {1}>{2}</{0}>";
47      
48      /**
49       * Pattern for an element with children but no attributes.
50       */
51      private static final String   CHILDREN_AND_NO_ATTRIBUTES = "<{0}>{1}</{0}>";
52      
53      /**
54       * Pattern for an element with neither children or attributes.
55       */
56      private static final String   NO_CHILDREN_NO_ATTRIBUTES = "<{0}></{0}>";
57      
58      /**
59       * Pattern for an element with attributes but no children.
60       */
61      private static final String   NO_CHILDREN_AND_ATTRIBUTES = "<{0} {1}></{0}>";
62      
63      /**
64       * The name of the element.
65       */
66      private final String   name;
67      
68      /**
69       * The parent of the element.
70       */
71      private Element parent;
72      
73      /**
74       * The attributes of the element.
75       */
76      private final Map   attributes = new HashMap  ();
77      
78      /**
79       * The children of the element.
80       */
81      private final List   children = new ArrayList  ();
82      
83      /**
84       * Constructs an element with the specified name and with no parent element.
85       * 
86       * @param name the name of the element.
87       */
88      public Element(final String   name) 
89      {
90          this(null, name);
91      }
92      
93      /**
94       * Constructs an element with the specified name and parent element.
95       * 
96       * @param parent the parent of the element (null is permitted).
97       * @param name the name of the element.
98       */
99      public Element(final Element parent, final String   name) 
100     {
101         super();
102         this.parent = parent;
103         this.name = name;
104     }
105     
106     /**
107      * Adds an attribute with the specified name and value if the value isn't null. 
108      * If an attribute with the specified name exists, it will be overwritten. 
109      * 
110      * @param name the name of the attribute.
111      * @param value the value of the attribute.
112      * @return the current element.
113      */
114     public Element addAttribute(final String   name, final String   value)
115     {
116         return addAttribute(name, value, true);
117     }
118     
119     /**
120      * Adds an attribute with the specified name and value if the specified condition
121      * is true and the value isn't null. 
122      * If an attribute with the specified name exists, it will be overwritten.
123      *  
124      * @param name the name of the attribute.
125      * @param value the value of the attribute.
126      * @param condition the condition to check.
127      * @return the current element.
128      */
129     public Element addAttribute(final String   name, String   value, final boolean condition)
130     {
131         if(condition && value != null)
132         {
133             Object   o = (Object  )attributes.get(name);
134             if(o != null && o instanceof String  )
135                 value = o + " " + value;
136             
137             attributes.put(name, value);
138         }
139         return this;
140     }
141     
142     /**
143      * Creates and adds a child with the specified name to the end of the children list.
144      * The parent of the child will be the current element.
145      * 
146      * @param name the name of the child element.
147      * @return the child element.
148      */
149     public Element addChild(final String   name) 
150     {
151         final Element child = new Element(this, name);
152         children.add(child);
153         return child;
154     }
155 
156     /**
157      * Creates and adds a child with the specified name to the start of the children list.
158      * The parent of the child will be the current element.
159      * 
160      * @param name the name of the child element.
161      * @return the child element.
162      */
163     public Element addChildFirst(final String   name) 
164     {
165         final Element child = new Element(this, name);
166         children.add(0, child);
167         return child;
168     }
169     
170     /**
171      * Adds the specified child to the end of the children list if non-null.
172      * The parent of the child will be set to the current element.
173      * 
174      * @param child the child element.
175      * @return the current element.
176      */
177     public Element addChild(final Element child) 
178     {
179         if(child != null)
180         {
181             child.parent = this;
182             children.add(child);
183         }
184         return this;
185     }
186     
187     /**
188      * Creates and adds a text-child to the end of the children list if non-empty.
189      *
190      * @param text the text of the child.
191      * @return the current element.
192      */
193     public Element addText(final String   text)
194     {
195         if(text != null && text.length() > 0)
196         {
197             children.add(text);
198         }
199         return this;
200     }
201     
202     /**
203      * Returns true if the element has an attribute with the specified name; false otherwise.
204      * 
205      * @return true if the element has an attribute with the specified name; false otherwise.
206      */
207     public boolean hasAttribute(final String   name)
208     {
209         return name != null && attributes.containsKey(name);
210     }
211     
212     /**
213      * Returns true if the element has any attributes; false otherwise.
214      * 
215      * @return true if the element has any attributes; false otherwise.
216      */
217     public boolean hasAttributes()
218     {
219         return !attributes.isEmpty();
220     }
221 
222     /**
223      * Returns true if the element has any children; false otherwise.
224      * 
225      * @return true if the element has any children; false otherwise.
226      */
227     public boolean hasChildren()
228     {
229         return !children.isEmpty();
230     }
231     
232     /**
233      * Returns the parent of the element.
234      * 
235      * @return the parent of the element.
236      */
237     public Element pop()
238     {
239         return parent;
240     }
241     
242     /**
243      * Returns the string representation of the element.
244      * 
245      * @return the string representation of the element.
246      */
247     public String   toString()
248     {
249         if(hasAttributes() && hasChildren())
250         {
251             return MessageFormat.format(CHILDREN_AND_ATTRIBUTES, new Object  [] { name, attributesString(), childrenString()});
252         }
253         if(hasAttributes() && !hasChildren())
254         {
255             return MessageFormat.format(NO_CHILDREN_AND_ATTRIBUTES, new Object  [] { name, attributesString() });
256         }
257         if(!hasAttributes() && hasChildren())
258         {
259             return MessageFormat.format(CHILDREN_AND_NO_ATTRIBUTES, new Object  [] { name, childrenString() });
260         }
261         return MessageFormat.format(NO_CHILDREN_NO_ATTRIBUTES, new Object  [] { name });
262     }
263     
264     /**
265      * Returns the string representation of the attributes of the element.
266      * 
267      * @return the string representation of the attributes of the element.
268      */
269     private String   attributesString()
270     {
271         final StringBuffer   sb = new StringBuffer  ();
272         for(final Iterator   i = attributes.keySet().iterator(); i.hasNext(); )
273         {
274             final Object   key   = i.next();
275             final Object   value = attributes.get(key);
276             sb.append((sb.length() > 0 ? " " : "") + MessageFormat.format(ATTRIBUTE, new Object  [] { key, value }));
277         }
278         return sb.toString();
279     }
280 
281     /**
282      * Returns the string representation of the children of the element.
283      * 
284      * @return the string representation of the children of the element.
285      */
286     private String   childrenString()
287     {
288         final StringBuffer   sb = new StringBuffer  ();
289         for(final Iterator   i = children.iterator(); i.hasNext(); )
290         {
291             sb.append(i.next());
292         }
293         return sb.toString();
294     }
295 }
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