[jboss-cvs] jboss-seam/ui/src/main/java/org/jboss/seam/ui/validator ...

[Peter Muir]

  User: pmuir   
  Date: 07/09/27 08:01:19

  Added:       ui/src/main/java/org/jboss/seam/ui/validator 
                        FormattedTextValidator.java
  Log:
  JBSEAM-1929, update wiki example, add to blog example
  
  Revision  Changes    Path
  1.1      date: 2007/09/27 12:01:19;  author: pmuir;  state: Exp;jboss-seam/ui/src/main/java/org/jboss/seam/ui/validator/FormattedTextValidator.java
  
  Index: FormattedTextValidator.java
  ===================================================================
  package org.jboss.seam.ui.validator;
  
  import java.io.Reader;
  import java.io.Serializable;
  import java.io.StringReader;
  
  import javax.faces.application.FacesMessage;
  import javax.faces.component.UIComponent;
  import javax.faces.context.FacesContext;
  import javax.faces.validator.ValidatorException;
  
  import org.jboss.seam.text.SeamTextLexer;
  import org.jboss.seam.text.SeamTextParser;
  
  import antlr.RecognitionException;
  import antlr.TokenStreamException;
  
  /**
   * Formatted Text validator
   * 
   * Use as a JSF validator on an input control that allows entering Seam Text
   * markup.
   * <p>
   * The Seam Text parser has a disabled default error handler, catch exceptions
   * as appropriate if you display Seam Text (see <a
   * href="http://www.doc.ic.ac.uk/lab/secondyear/Antlr/err.html">http://www.doc.ic.ac.uk/lab/secondyear/Antlr/err.html</a>)
   * and call the static convenience method
   * <tt>FormattedTextValidator.getErrorMessage(originalText, recognitionException)</tt>
   * if you want to display or log a nice error message.
   * 
   * @author matthew.drees
   * @author Christian Bauer
   */
  public class FormattedTextValidator implements javax.faces.validator.Validator,
          Serializable {
      private static final long serialVersionUID               = 1L;
  
      private static final int  NUMBER_OF_CONTEXT_CHARS_AFTER  = 10;
      private static final int  NUMBER_OF_CONTEXT_CHARS_BEFORE = 10;
  
      String                    firstError;
  
      /**
       * Validate the given value as well-formed Seam Text. If there are parse
       * errors, throw a ValidatorException including the first parse error.
       */
      public void validate(FacesContext context, UIComponent component,
              Object value) throws ValidatorException {
          firstError = null;
          if (value == null) {
              return;
          }
  
          if (!(value instanceof String)) {
              throw new IllegalArgumentException("Value is not a string: "
                      + value);
          }
          String text = (String) value;
          Reader r = new StringReader(text);
          SeamTextLexer lexer = new SeamTextLexer(r);
          SeamTextParser parser = new SeamTextParser(lexer);
          try {
              parser.startRule();
          }
          // Error handling for ANTLR lexer/parser errors, see
          // http://www.doc.ic.ac.uk/lab/secondyear/Antlr/err.html
          catch (TokenStreamException tse) {
              // Problem with the token input stream
              throw new RuntimeException(tse);
          } catch (RecognitionException re) {
              // A parser error, just log and swallow
              if (firstError == null) {
                  firstError = getErrorMessage(text, re);
              }
          }
  
          if (firstError != null) {
              throw new ValidatorException(new FacesMessage("Invalid markup: "
                      + firstError));
          }
      }
  
      /**
       * Extracts the error from the <tt>RecognitionException</tt> and generates
       * a message with some helpful context.
       * 
       * @param originalText
       *            the original Seam Text markup as fed into the parser
       * @param re
       *            an ANTLR <tt>RecognitionException</tt> thrown by the parser
       * @return an error message with some helpful context about where the error
       *         occured
       */
      public static String getErrorMessage(String originalText,
              RecognitionException re) {
          int beginIndex = Math.max(re.getColumn() - 1
                  - NUMBER_OF_CONTEXT_CHARS_BEFORE, 0);
          int endIndex = Math.min(re.getColumn() + NUMBER_OF_CONTEXT_CHARS_AFTER,
                  originalText.length());
          String msg = re.getMessage() + " at '" + (beginIndex == 0 ? "" : "...")
                  + originalText.substring(beginIndex, endIndex)
                  + (endIndex == originalText.length() ? "" : "...") + "'";
          return msg.replace("\n", " ").replace("\r", " ").replace("\uFFFF",
                  "[END OF TEXT]");
      }
  }