MuleSoft SAX Parser Error "Content is not allowed in prolog"

The Mule SAX parser error that "Content is not allowed in the prolog" happens when trying to parse XML content that is not valid XML and normally refers to a different encoding or BOM before the XML declaration or invalid text such as:

1. The different encoding causes the error, and it occurs because the file encoding format is not correct.
2. Many text editors auto-add BOM to the UTF-8 file.
3. At the beginning of the XML declaration, any text will cause the "Content is not allowed in prolog" error
 

SOLUTION

1. You might add a JVM system property file.encoding=UTF-8 to ensure that UTF-8 is the encoding format or whatever you need. You can specify -Dfile.encoding=UTF-8 when invoking the application
2. Remove the BOM from the UTF-8 file
3. Delete any text before the XML declaration