README.md

Nice XML messages

A mini library to output rich error messages when doing some XML validation with the standard Java DOM API.

For example, if an XML parse exception occurs, instead of

javax.xml.transform.TransformerException: The entity "amb" was referenced, but not declared.

the exception would have the following message:

XML parsing error (in /some/file.xml)
    1| <?xml version="1.0" encoding="UTF-8" standalone="no"?>
    2| <list>
    3|     <list foo="&amb;"/>
                           ^ The entity "amb" was referenced, but not declared.
    4| </list>

or

Error at /some/file.xml:3:21 - The entity "amb" was referenced, but not declared.

if you prefer shorter messages.

The point is that it displays the file position.

This library would be most useful when doing some manual validation/parsing on the DOM afterwards, eg when reading a configuration file.

It provides an interface which looks like this:

public interface XmlErrorReporter {

  void warn(org.w3c.dom.Node location, String message, Object... formatArgs);

  // and other variants like error, fatalError, etc

}

After parsing your file appropriately, you can do your parsing and report messages to the user easily:

  void parseListElement(Element elt, XmlErrorReporter err) {
    for (Element item : DomUtils.elementsIn(elt)) {
        if (!item.getNodeName().equals("item")) {
            err.warn(item, "Unexpected element {0} will be ignored", item.getNodeName());
            continue;
        }

        // process item
    }
  }

The warning would include the position of the element.