For example, below violation will lead to an unexpected exception when viewing PMD violations report:

The String literal "<<<" appears 4 times in this file; the first occurrence is on line 149

The exception looks like:

WicketMessage: Malformed tag (line 7, column 34)
[markup = onclick="window.open('http://pmd.sourceforge.net/rules/strings.html#AvoidDuplicateLiterals', 'AvoidDuplicateLiterals')">

 ]
                        
   The String literal "<<<" appears 4 times in this file; the first occurrence is on line 149
                                            

                                                onclick="window.open('http://pmd.sourceforge.net/rules/strings.html#AvoidDuplicateLiterals', 'AvoidDuplicateLiterals')">
                        
                        ]
                        
                                                    The String literal "<<<" appears 4 times in this file; the first occurrence is on line 149
                                             , index = 1, current = [Raw markup]]

Root cause:

java.text.ParseException: Malformed tag (line 7, column 34)
     at org.apache.wicket.markup.parser.XmlPullParser.next(XmlPullParser.java:305)
     at org.apache.wicket.markup.parser.XmlPullParser.nextTag(XmlPullParser.java:421)
     at org.apache.wicket.markup.parser.filter.WicketTagIdentifier.nextTag(WicketTagIdentifier.java:77)
     at org.apache.wicket.markup.parser.filter.HtmlHandler.nextTag(HtmlHandler.java:78)

....