ActionEvent


1   package org.apache.turbine.modules;
2   
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56  
57  import java.lang.reflect.InvocationTargetException  ;
58  import java.lang.reflect.Method  ;
59  import java.util.Enumeration  ;
60  
61  import org.apache.fulcrum.parser.ParameterParser;
62  import org.apache.turbine.RunData;
63  import org.apache.turbine.Turbine;
64  import org.apache.turbine.TurbineException;
65  
66  /**
67   * <p>
68   *
69   * This is an alternative to the Action class that allows you to do
70   * event based actions. Essentially, you label all your submit buttons
71   * with the prefix of "eventSubmit_" and the suffix of "methodName".
72   * For example, "eventSubmit_doDelete". Then any class that subclasses
73   * this class will get its "doDelete(RunData data)" method executed.
74   * If for any reason, it was not able to execute the method, it will
75   * fall back to executing the doPeform() method which is required to
76   * be implemented.
77   *
78   * <p>
79   *
80   * Limitations:
81   *
82   * <p>
83   *
84   * Because ParameterParser makes all the key values lowercase, we have
85   * to do some work to format the string into a method name. For
86   * example, a button name eventSubmit_doDelete gets converted into
87   * eventsubmit_dodelete. Thus, we need to form some sort of naming
88   * convention so that dodelete can be turned into doDelete.
89   *
90   * <p>
91   *
92   * Thus, the convention is this:
93   *
94   * <ul>
95   * <li>The variable name MUST have the prefix "eventSubmit_".</li>
96   * <li>The variable name after the prefix MUST begin with the letters
97   * "do".</li>
98   * <li>The first letter after the "do" will be capitalized and the
99   * rest will be lowercase</li>
100  * </ul>
101  *
102  * If you follow these conventions, then you should be ok with your
103  * method naming in your Action class.
104  *
105  * @author <a HREF="mailto:jon@latchkey.com">Jon S. Stevens </a>
106  * @version $Id: ActionEvent.java,v 1.5 2004/11/12 10:26:31 epugh Exp $
107  */
108 public abstract class ActionEvent
109     extends Action
110 {
111     /**
112      * You need to implement this in your classes that extend this class.
113      *
114      * @param data Turbine information.
115      * @exception Exception a generic exception.
116      */
117     public abstract void doPerform( RunData data )
118         throws Exception  ;
119 
120     /** The name of the button to look for. */
121     protected static final String   BUTTON = "eventSubmit_";
122     /** The length of the button to look for. */
123     protected static final int BUTTON_LENGTH = BUTTON.length();
124     /** The prefix of the method name. */
125     protected static final String   METHOD_NAME_PREFIX = "do";
126     /** The length of the method name. */
127     protected static final int METHOD_NAME_LENGTH = METHOD_NAME_PREFIX.length();
128     /** The length of the button to look for. */
129     protected static final int LENGTH = BUTTON.length();
130 
131     /**
132      * This overrides the default Action.perform() to execute the
133      * doEvent() method. If that fails, then it will execute the
134      * doPerform() method instead.
135      *
136      * @param data Turbine information.
137      * @exception Exception a generic exception.
138      */
139     protected void perform( RunData data )
140         throws Exception  
141     {
142         try
143         {
144             executeEvents(data);
145         }
146         catch (NoSuchMethodException   e)
147         {
148             doPerform( data );
149         }
150         catch (InvocationTargetException   ite)
151         {
152             // i have not seen this exception, in stacktraces generated
153             // while doing my own testing on jdk1.3.1 and earlier.  But
154             // see it increasingly from stacktraces reported by others.
155             // Its printStackTrace method should do The Right Thing, but
156             // I suspect some implementation is not.
157             // Unwrap it here, so that the original cause does not get lost.
158             Throwable   t = ite.getTargetException();
159             if (t instanceof Exception  ) 
160             {
161                 throw (Exception  )t;
162             }
163             else if (t instanceof java.lang.Error  ) 
164             {
165                 throw (java.lang.Error  )t;
166             }
167             else 
168             {
169                 // this should not happen, but something could throw
170                 // an instance of Throwable
171                 throw new TurbineException(t);
172             }
173         }
174     }
175 
176     public void execute(RunData data)
177         throws Exception  
178     {
179         perform(data);
180     }
181 
182     /**
183      * This method should be called to execute the event based system.
184      *
185      * @param data Turbine information.
186      * @exception Exception a generic exception.
187      */
188     public void executeEvents(RunData data)
189         throws Exception  
190     {
191         // Name of the button.
192         String   theButton = null;
193         // Parameter parser.
194         ParameterParser pp = data.getParameters();
195         // The arguments to pass to the method to execute.
196         Object  [] args = new Object  [1];
197         // The arguments to the method to find.
198         Class  [] classes = new Class  [1];
199         classes[0] = RunData.class;
200 
201         String   button = pp.convert(BUTTON);
202 
203         // Loop through and find the button.
204         for (Enumeration   e = pp.keys() ; e.hasMoreElements() ;)
205         {
206             String   key = (String  ) e.nextElement();
207             if (key.startsWith(button))
208             {
209                 theButton = formatString(key);
210                 break;
211             }
212         }
213 
214         if (theButton == null)
215         {
216             throw new NoSuchMethodException  (
217                 "ActionEvent: The button was null");
218         }
219 
220         Method   method = getClass().getMethod(theButton, classes);
221         args[0] = data;
222         method.invoke(this, args );
223     }
224 
225     /**
226      * This method does the conversion of the lowercase method name
227      * into the proper case.
228      *
229      * @param input The unconverted method name.
230      * @return A string with the method name in the proper case.
231      */
232     protected final String   formatString(String   input)
233     {
234         String   methodName = input;
235         
236         // check for image submission
237         if (input.endsWith(".x") || input.endsWith(".y"))
238         {
239            methodName = methodName.substring(0, input.length() - 2);
240         }
241         
242         String   fold =
243             Turbine.getConfiguration().getString(
244                 Turbine.PP_URL_CASE_FOLDING, 
245                 ParameterParser.URL_CASE_FOLDING_LOWER).toLowerCase();
246 
247         if (! fold.equals(ParameterParser.URL_CASE_FOLDING_NONE))
248         {
249             methodName = 
250                 methodName.substring(BUTTON_LENGTH + METHOD_NAME_LENGTH);
251 
252             return (METHOD_NAME_PREFIX + firstLetterCaps(methodName));
253         }
254         else
255         {
256             return methodName.substring(BUTTON_LENGTH);
257         }
258     }
259 
260     /**
261      * Makes the first letter caps and the rest lowercase.
262      *
263      * @param data The input string.
264      * @return A string with the described case.
265      */
266     private final String   firstLetterCaps( String   data )
267     {
268         String   firstLetter = data.substring(0, 1).toUpperCase();
269         String   restLetters = data.substring(1).toLowerCase();
270         return firstLetter + restLetters;
271     }
272 }
273
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