How to put labels over geom_bar for each bar in R with ggplot2

Try this:

ggplot(data=dat, aes(x=Types, y=Number, fill=sample)) + 
     geom_bar(position = 'dodge', stat="identity") +
     geom_text(aes(label=Number), position=position_dodge(width=0.9), vjust=-0.25)