ErrorCatchingVisitor


1   /* @author Rich Morris
2    * Created on 19-Jun-2003
3    *
4    * This code is covered by a Creative Commons
5    * Attribution, Non Commercial, Share Alike license
6    * <a HREF="http://creativecommons.org/licenses/by-nc-sa/1.0">License</a>
7    */
8   package org.lsmp.djep.xjep;
9   //import org.lsmp.djep.matrixParser.*;
10  import org.nfunk.jep.*;
11  
12  /**
13   * An abstract ParserVisitor
14   * which adds some useful error handeling facilities.
15   * Visitors which require these facilities should extend this class.
16   * General format should be
17   * <pre>  
18   *  clearErrors();
19   *  Object res = (Node) node.jjtAccept(this,data);
20   *  if(hasErrors())
21   *      throw new ParseException(getErrors());
22   *</pre>
23   * @author Rich Morris
24   * Created on 19-Jun-2003
25   */
26  abstract public class ErrorCatchingVisitor extends DoNothingVisitor
27  {
28      /** The current error list. */
29      private Exception   error=null;
30  
31      /** calls jjtAccept inside a try catch block, adding the error if necessary */
32      public Object   acceptCatchingErrors(Node node,Object   data)
33      {
34          Object   res=null;
35          clearErrors();
36          try
37          {
38              res = node.jjtAccept(this,data);
39          }
40          catch (ParseException e) { addError(e); }
41          return res;
42      }
43      /** Reset the list of errors. */
44      public void clearErrors() { error = null;   }
45  
46      /** Are their any errors? */    
47      public boolean hasErrors() { return error != null; }
48      
49      /** Adds an error message to the list of errors. */
50      public void addError(Exception   e)   {error = e; }
51  
52      /** Returns the error messages.  */
53      public String   getErrorsMessage() {
54          if(error==null) return null;
55          else return error.getMessage();
56      }
57      /** Returns the Exception or null if no error. */
58      public Exception   getError() { return error; }
59  }
60
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