N.J. Stat. § 40:48-2.7
Complaints or orders issued by a public officer pursuant to an ordinance adopted under this act shall be served upon persons either personally or by registered mail, but if the whereabouts of such persons is unknown and the same cannot be ascertained by the public officer in the exercise of reasonable diligence, and the public officer shall make an affidavit to that effect, then the serving of such complaint or order upon such persons may be made by publishing the same once in a newspaper printed and published in the municipality, or, in the absence of such newspaper, in one printed and published in the county and circulating in the municipality in which the buildings are located. A copy of such complaint or order shall be posted in a conspicuous place on premises affected by the complaint or order. A copy of such complaint or order shall be duly recorded or lodged for record with the county recording officer of the county in which the building is located.
N.J.S. § 40:48-2.7