FOP 2.2 - loading fonts

Hi guys,

I got problems with loading fonts. fop.xml config got this definition of a font:
	<font metrics-url="arial.xml"
         	kerning="yes"
                 embed-url="arial.ttf">
                 <font-triplet name="Arial" style="normal" weight="normal"/>
         </font>

When the PDF is rendered, there's an error message:
"2017-07-05 18:13:10.508 ERROR 3120 --- [nio-6200-exec-1] org.apache.fop.pdf.PDFFactory            : Failed to embed 
font [org.apache.fop.fonts.LazyFont@2402f627{Arial 
Bold}{metrics-url=arialbd.xml,embed-url=arialbd.ttf,kerning=true,advanced=true}] Arial-BoldMT

java.io.IOException: 'loca' table not found, happens when the font file doesn't contain TrueType outlines (trying to 
read an OpenType CFF font maybe?)
         at org.apache.fop.fonts.truetype.TTFFile.readIndexToLocation(TTFFile.java:180)
         at org.apache.fop.fonts.truetype.TTFSubSetFile.readFont(TTFSubSetFile.java:479)
         at org.apache.fop.pdf.PDFFactory.getFontSubsetBytes(PDFFactory.java:1368)
         at org.apache.fop.pdf.PDFFactory.makeFontFile(PDFFactory.java:1299)
         at org.apache.fop.pdf.PDFFactory.makeFontDescriptor(PDFFactory.java:1223)
         at org.apache.fop.pdf.PDFFactory.makeFont(PDFFactory.java:944)
         at org.apache.fop.pdf.PDFResources.addFonts(PDFResources.java:137)"

When I configure FOP to autodetect the installed fonts of the operating system, then of course all installed fonts are 
discovered and they are available for using them in the PDFs - included this arial.ttf which loading is broken with the 
error above. (anyway, this setup of this font has been working with FOP 0.95)

Why do I want to specify and load fonts via fop.xml? Because the application is a spring-boot app and it's going to run 
in a docker image where noone knows what kinda fonts will be installed and if they would be accessible to FOP.

Any ideas how could I configure the font loading properly?

Thanks,
J.