Beginning Java EE 6 with GlassFish 3, Second Edition

CHAPTER 11 ■ PAGES AND COMPONENTSwhere expr is a valid expression that is parsed and interpreted. As of JSP 2.1, you can also use thefollowing syntax:#{expr}The ${expr} and #{expr} statements will be parsed and evaluated in exactly the same manner forJSPs. However, for JSF, it is a different matter because, as you’ll see, JSF pages have a life cycle differentfrom that of JSPs. You can use ${expr} for expressions that are evaluated immediately (the expression iscompiled when the JSP is compiled and is evaluated once, when the JSP executes) and #{expr} forexpressions with a deferred evaluation (the expression is not evaluated until its value is needed). Thesetwo ELs have been unified, so a JSP and a JSF page can use both, but with the life-cycle difference.EL expressions can use most of the usual Java operators:• Arithmetic: +, -, *, / (div), % (mod)• Relational: == (eq), != (ne), < (lt), > (gt), = (ge)• Logical: && (and), || (or), ! (not)• Other: (), empty, [], .Note that some operators have both symbolic and word variants (> can be gt, / can be div, and soon). These equivalents allow you to make your JSP XML compliant while avoiding using entity references(such as &lt; for