Well, now that Stoian Azarov has blurted out the answer and robbed you of the learning opportunity of looking up the EL syntax, you know what the syntax error was. You use either of the dot (.) or the bracket () operators, but never both at the same time on a single term.
In head first servetls and jsp(2nd edition), chapter-8 scripltess jsp pg-372
1.if the expression has a variable followed by bracket,the left hand varaible can be a Map,Bean ,List,Array
2.if the thing inside brackets is a string literal ,it can be a map key ,bean property or an index.
Here developer is a bean with builds as a property which itself is a bean with build_number property.
I just want to try different ways we can access beans using El that why i am using the general(bracket) operator.