In general the Jedis will ignore you allowing you to take free blasts at them. Occasionally there will be one jedi that goes after you but that is rare. Ignore the temple guards until you cleared the first wave of Jedis and focusing on protecting one bookcase is easier than protecting all of them. If your fighting a Jedi that is using force block shoot their feet.
Personally I would us an Engineer or Vanguard. If your playing as a Vanguard and FF is on, be careful not to destroy your own bookcases. If FF is off, you can drop a mine on pairs of Jedis and use the rocket launcher to take out single ones.
Its much easier if you use an Engineer though. Detpacks have similar power as to mines and the shotgun will take out most Jedis with 1 - 3 blasts. You can also use the fusion cutter to repair bookcases.
Often times the hardest part of that objective is clearing the Jedis that are there in the first place. Once you can get past that first half, defending is easy.