code: void writeRequireConfigPropsXml(List<ConfigPropType> props, Writer out, int indent) throws IOException
     {
        if (props == null || props.size() == 0)
           return;
        for (ConfigPropType prop : props)
        {
           if (prop.isRequired())
           {
              writeIndent(out, indent);
              out.write("<required-config-property>");
              writeEol(out);
  
              writeIndent(out, indent + 1);
              out.write("<config-property-name>" + prop.getName() + "</config-property-name>");
              writeEol(out);
  
              writeIndent(out, indent);
              out.write("</required-config-property>");
              writeEol(out);
           }
        }
        writeEol(out);
     }
docs: Output required config props xml part
  
  @param props  config properties
  @param out    Writer
  @param indent space number
  @throws IOException ioException