Difference between JSP EL, JSF EL and Unified EL

• Jun 2002: JSTL 1.0 was introduced with EL for first time. It were those ${} things which works in JSTL tags only. It is designed to call Javabean get methods.

• Nov 2003: JSP 2.0 was introduced and EL was moved from JSTL 1.0 to JSP 2.0 in javax.servlet.jsp.el package and it became standard EL as part of J2EE 1.4 standard. JSTL 1.1 was shipped without EL. Now ${} works outside JSTL tags in JSP template text as well.

• Mar 2004: JSF 1.0 was introduced with deferred EL in javax.faces.el package. It were those #{} things which works inside JSF tags only. The difference with standard JSP EL ${} is that it doesn't only do get, but can also do set. This was mandatory for managed bean auto-creation and setting the values of input components. The standard EL ${} works in JSF output tags as well, but they won't auto-create beans if they don't exist in scope yet and they won't set input values.

• May 2005: While still preparing for new JSP 2.1 which should be released May 2006, deferred EL #{} was extracted from JSF and combined with standard EL ${} in the javax.el package. At that point, it became unified EL which was introduced with JSF 1.2 and became later part of JSP 2.1 and Java EE 5 standard. The #{} can now also be used in JSP tags to get values, but not to set values. The ${} can now in JSP also auto-create managed beans, but not set values.

• Nov 2006: Facelets was introduced as successor of JSP. It allowed for use of #{} in template text outside JSF tags, as substitute for <h:outputText> without any attributes. It also treats ${} as #{}, so they both behave the same in Facelets.

• Dec 2009: EL was extracted from JSP specification and became a standalone specification which will be maintained independently from JSP, the first version being EL 2.2 (JSR-245), analogous with JSP 2.2. Main new feature is calling parameterized methods instead of only calling Javabean getters/setters inside #{} syntax, e.g. #{bean.method(argument)}. Furthermore, Facelets became part of Java EE 6 standard.

• Jun 2013: EL 3.0 was introduced which comes with a standalone EL processor, allowing usage in a plain Java SE application. Other main new features are the new string concatenation operator +=, new operations for collection objects, including streams and Lambda expressions -> (even on Java 6/7!) and importing constants into EL scope.

Adding to BalusC's answer...

EL was originally conceived by and implemented by Nathan Abramson of Art Technology Group in 2001. At the time the implementation was known as Simplest Possible Expression Language (SPEL). The implementation was later included in the JSTL1.0. Nathan was part of the JSR-052 Expert Group, and was credited in the JSTL specification as the driving force behind the expression language.

"Special mention to Nathan Abramson for being a driving force behind the expression language introduced in JSTL"