This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
If you are expecting a different answer (or) an extra piece of information then, here it is ...
If your attributes are primitives, then the string that we pass in the JSP file's custom tag, is auto-converted to the primitive.
However, if you want to set value of an attribute to an Object, an explicit setter method with proper parameter should be present in your tag handler and the syntax should be how 'gowher' mentioned in his explanation.