yyuc / juel

Java Unified Expression Language

JUEL - Java Unified Expression Language

JUEL is an implementation of the Unified Expression Language (EL), specified as part of the JSP 2.1 standard (JSR-245), which has been introduced in JEE5. Additionally, JUEL 2.2 implements the JSP 2.2 maintenance release specification for full JEE6 compliance.

Motivation

Once, the EL started as part of JSTL. Then, the EL made its way into the JSP 2.0 standard. Now, though part of JSP 2.1, the EL API has been separated into package javax.el and all dependencies to the core JSP classes have been removed.

In other words: the EL is ready for use in non-JSP applications!

Features

JUEL provides a lightweight and efficient implementation of the Unified Expression Language.

• High Performance – Parsing expressions is certainly the expected performance bottleneck. JUEL uses a hand-coded parser which is up to 10 times faster than the previously used (javacc) generated parser! Once built, expression trees are evaluated at highest speed.
• Pluggable Cache – Even if JUEL's parser is fast, parsing expressions is relative expensive. Therefore, it's best to parse an expression string only once. JUEL provides a default caching mechanism which should be sufficient in most cases. However, JUEL allows to plug in your own cache easily.
• Small Footprint – JUEL has been carefully designed to minimize memory usage as well as code size.
• Method Invocations – JUEL supports method invocations as in ${foo.matches('[0-9]+')}. Methods are resolved and invoked using the EL's resolver mechanism. As of JUEL 2.2, method invocations are enabled by default.
• VarArg Calls – JUEL supports Java 5 VarArgs in function and method invocations. E.g., binding String.format(String, String...) to function format allows for ${format('Hey %s','Joe')}. As of JUEL 2.2, VarArgs are enabled by default.
• Pluggable – JUEL can be configured to be transparently detected as EL implementation by a Java runtime environment or JEE application server. Using JUEL does not require an application to explicitly reference any of the JUEL specific implementation classes.

Documentation

Visit the JUEL site at Sourceforge.

Downloads

The JUEL distribution contains the following JAR files:

• juel-api-2.2.x.jar - the javax.el API classes.
• juel-impl-2.2.x.jar - the de.odysseus.el implementation classes.
• juel-spi-2.2.x.jar - the META-INF/service/javax.el.ExpressionFactory service provider resource. (You will need this if you have several expression language implementations on your classpath and want to force JUEL's implementation to be chosen by ExpressionFactory.newInstance()).

The JARs are also available via Maven:

<dependency>
  <groupId>de.odysseus.juel</groupId>
  <artifactId>juel-api</artifactId>
  <version>2.2.x</version>
</dependency>

<dependency>
  <groupId>de.odysseus.juel</groupId>
  <artifactId>juel-impl</artifactId>
  <version>2.2.x</version>
</dependency>

<dependency>
  <groupId>de.odysseus.juel</groupId>
  <artifactId>juel-spi</artifactId>
  <version>2.2.x</version>
</dependency>

Development

Visit the Github project.

Status

JUEL is considered production stable. The code is well tested (80% coverage) and feature complete.

License

JUEL is available under the Apache License, Version 2.0.

(c) 2006-2012 Odysseus Software