Dodi Suridi, 23, a supporter of the so-called Islamic State group (IS), helped make one of the bombs used on the day. He said he accepted the verdict as "the risk of being a terrorist".
Five assailants were killed by police during the attack and about 40 have since been arrested.
Prosecutors said Suridi altered gas canisters to provide bombs for two attackers who blew themselves up at a police post.
He was arrested the day after the attack.
A second IS supporter, 48-year-old Ali Hamka, was jailed for four years for attempting to source guns and ammunition for the attack. Hamka did not obtain the guns but was still found guilty of breaking anti-terror laws.
As he was led away from court, Suridi shouted "Allahu akbar", Arabic for God is great, and smiled at journalists in the court. Judge Achmad Fauzi said his actions had "disturbed the community and shaken the life of our nation".
He and Hamka both made a gesture that has come to be associated with IS, pointing one finger towards the sky.
The attack in January was the first attack linked to IS in south-east Asia but Indonesia has since suffered several attacks carried out under the group`s banner.
As Suridi and Hamka were appearing in court on Thursday, a man carrying a machete, suspected pipe bombs and an IS symbol launched an attack on officers near Jakarta before being shot dead by police.
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