Hrabák together with J. Grimm (1805–1874) and A. Beer (1815–1879) is the key figure shaping not only the mining school in Příbram, but also Czech mining engineering in general. He was active in the early days of the Industrial Revolution, and his educational work in this field was thus central to the development of entire industries. He consistently advocated the preservation of the existence of the mining school in Příbram, which, despite its importance for the development of industry and science in the monarchy, was for most of its existence in a precarious position vis-à-vis the imperial authorities, who wanted to centralise the mining engineering sciences in Vienna. Hrabák served as the Rector of the school during the crisis years (1879/80, 1885-1888), when the Academy was threatened with dissolution. Even so, he still managed to maintain a high level of teaching. His textbooks on steam engines were published in many European countries. His dictionaries of mining (1887) and metallurgy (1907) were of fundamental importance for the establishment of a unified terminology in the newly developing industrial fields. In order to defend the importance of the school`s existence in the centre of Bohemia, he analysed the history and present of mining production in the Bohemian lands and documented that at the turn of the 19th and 20th centuries it provided three quarters of the mining production of the entire monarchy. His analysis is a valuable historical material today. He also documented the history of mining education in his memorial book of the Příbram school, which well illustrates the status, atmosphere and vicissitudes of the educational system, which struggled with both bureaucracy and rapid changes in all fields of study.
For his merits in mining engineering he was awarded an honorary doctorate in Mining Engineering in 1907 as the first person ever to receive it. He lived to see the transformation of the school in the new Czechoslovak state, but his work belongs to the founding generation of the Příbram school. On the occasion of international meetings of Mining engineers – the symposium Mining Příbram in Science and Technology (from 1962 to the present), a commemorative medal was issued in honour of its three main figures: J. Grimm, A. Beer and J. Hrabák.
A newly discovered mineral with type locality in the Příbram area was named Hrabákite in his honour in 2020. (Meaning it was first described for the world here.)