Design pattern for multiple combinations

If I have to make a different database query depending on the presence or not of different parameters, which would be the correct design pattern to avoid too many if-else with the different combinations ? Let's say I have parameters a, b, c (the amount can grow in the future), I'm using repositories so I would have to make a call something like this

public Foo getFoo(String a, String b, String c){
   Foo foo;
   if(a!=null && !a.isEmpty() && b!=null && !b.isEmpty() && c!=null && !c.isEmpty())
      foo = repository.findByAAndBAndC(a,b,c);
   if((a==null || a.isEmpty()) && b!=null && !b.isEmpty() && c!=null && !c.isEmpty())
      foo = repository.findByBAndC(b,c);
   if((a!=null && !a.isEmpty()) && (b==null || b.isEmpty()) && c!=null && !c.isEmpty())
      foo = repository.findByAAndC(a,c);
   if((a==null || a.isEmpty()) && (b==null || b.isEmpty()) && !b.isEmpty() && c!=null && !c.isEmpty())
      foo = repository.findByC(c);
   if((a==null || a.isEmpty()) && (b==null || b.isEmpty()) && !b.isEmpty() && (b==null || b.isEmpty()))
      foo = repository.findOne();
   etc.
   .
   .
   .
   return foo;
}

How can that be better structured ?