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<?xml version="1.0"?>
<!--
Copyright 2002,2004 The Apache Software Foundation.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<document>
<properties>
<title>Commons JEXL Syntax</title>
</properties>
<body>
<section name="Overview">
<p>
This reference is split up into the following sections:
<ol>
<li><a href="#Language Elements">Language Elements</a></li>
<li><a href="#Literals">Literals</a></li>
<li><a href="#Functions">Functions</a></li>
<li><a href="#Operators">Operators</a></li>
<li><a href="#Conditional">Conditional Statements</a></li>
</ol>
</p>
<p>
For more technical information about the JEXL Grammar, you can find the
<a href="https://javacc.dev.java.net/">JavaCC</a> grammar for JEXL
here: <a href="http://svn.apache.org/viewcvs.cgi/jakarta/commons/proper/jexl/trunk/src/java/org/apache/commons/jexl/parser/Parser.jj?view=markup">Parser.jj</a>
</p>
</section>
<section name="Language Elements">
<table>
<tr><th width="15%">Item</th><th>Description</th></tr>
<tr>
<td>Comments</td>
<td>
Specified using <code>##</code> and extend to the end of line, e.g.
<source>## This is a comment</source>
</td>
</tr>
<tr>
<td>Identifiers / variables</td>
<td>
Must start with <code>a-z</code>, <code>A-Z</code>, <code>_</code> or <code>$</code>.
Can then be followed by <code>0-9</code>, <code>a-z</code>, <code>A-Z</code>, <code>_</code> or <code>$</code>.
e.g.
<ul>
<li>Valid: <code>var1</code>,<code>_a99</code>,<code>$1</code></li>
<li>Invalid: <code>9v</code>,<code>!a99</code>,<code>1$</code></li>
</ul>
<p>
JEXL also supports <code>ant-style</code> variables, e.g. <source>my.dotted.var</source>
is a valid variable name.
</p>
<p>
<strong>NOTE:</strong> JEXL does not support variables with hyphens in them, e.g.
<source>commons-logging</source> is not a valid variable, but instead is treated as a
subtraction of the variable <code>logging</code> from the variable <code>commons</code>
</p>
</td>
</tr>
<tr>
<td>Scripts</td>
<td>
A script in Jexl is made up of zero or more statements. Scripts can be read from a String, File or URL.
</td>
</tr>
<tr>
<td>Statements</td>
<td>
A statement can be the empty statement, the semicolon (<code>;</code>) , block, assignment or an expression.
Statements are optionally terminated with a semicolon.
</td>
</tr>
<tr>
<td>Block</td>
<td>
A block is simply multiple statements inside curly braces (<code>{, }</code>).
</td>
</tr>
</table>
</section>
<section name="Literals">
<table>
<tr><th width="15%">Item</th><th>Description</th></tr>
<tr>
<td>Integer Literals</td>
<td>1 or more digits from <code>0</code> to <code>9</code></td>
</tr>
<tr>
<td>Floating point Literals</td>
<td>
1 or more digits from <code>0</code> to <code>9</code>, followed
by a decimal point and then one or more digits from
<code>0</code> to <code>9</code>.
</td>
</tr>
<tr>
<td>String literals</td>
<td>
Can start and end with either <code>'</code> or <code>"</code>, e.g.
<source>"Hello world"</source> and
<source>'Hello world'</source> are equivalent.
</td>
</tr>
<tr>
<td>Boolean literals</td>
<td>
The literals <code>true</code> and <code>false</code> can be used, e.g.
<source>val1 == true</source>
</td>
</tr>
<tr>
<td>Null literal</td>
<td>
The null value is represented as in java using the literal <code>null</code>, e.g.
<source>val1 == null</source>
</td>
</tr>
</table>
</section>
<section name="Functions">
<table>
<tr><th width="15%">Function</th><th>Description</th></tr>
<tr>
<td>empty</td>
<td>
Returns true if the expression following is either:
<ol>
<li><code>null</code></li>
<li>An empty string</li>
<li>An array of length zero</li>
<li>A collection of size zero</li>
<li>An empty map</li>
</ol>
<source>empty(var1)</source>
</td>
</tr>
<tr>
<td>size</td>
<td>
Returns the information about the expression:
<ol>
<li>Length of an array</li>
<li>Size of a List</li>
<li>Size of a Map</li>
<li>Size of a Set</li>
<li>Length of a string</li>
</ol>
<source>size("Hello")</source> returns 5.
</td>
</tr>
</table>
</section>
<section name="Operators">
<table>
<tr><th width="15%">Operator</th><th>Description</th></tr>
<tr>
<td>Boolean <code>and</code></td>
<td>
The usual <code>&&</code> operator can be used as well as the word <code>and</code>, e.g.
<source>cond1 and cond2</source> and
<source>cond1 && cond2</source> are equivalent
</td>
</tr>
<tr>
<td>Boolean <code>or</code></td>
<td>
The usual <code>||</code> operator can be used as well as the word <code>or</code>, e.g.
<source>cond1 or cond2</source> and
<source>cond1 || cond2</source> are equivalent
</td>
</tr>
<tr>
<td>Boolean <code>not</code></td>
<td>
The usual <code>!</code> operator can be used as well as the word <code>not</code>, e.g.
<source>!cond1</source> and
<source>not cond1</source> are equivalent
</td>
</tr>
<tr>
<td>Bitwise <code>and</code></td>
<td>
The usual <code>&</code> operator is used, e.g.
<source>33 & 4</source>, 0010 0001 & 0000 0100 = 0.
</td>
</tr>
<tr>
<td>Bitwise <code>or</code></td>
<td>
The usual <code>|</code> operator is used, e.g.
<source>33 | 4</source>, 0010 0001 | 0000 0100 = 0010 0101 = 37.
</td>
</tr>
<tr>
<td>Bitwise <code>xor</code></td>
<td>
The usual <code>^</code> operator is used, e.g.
<source>33 ^ 4</source>, 0010 0001 ^ 0000 0100 = 0010 0100 = 37.
</td>
</tr>
<tr>
<td>Bitwise <code>complement</code></td>
<td>
The usual <code>~</code> operator is used, e.g.
<source>~33</source>, ~0010 0001 = 1101 1110 = -34.
</td>
</tr>
<tr>
<td>Equality</td>
<td>
The usual <code>==</code> operator can be used as well as the abbreviation <code>eq</code>.
For example
<source>val1 == val2</source> and
<source>val1 eq val2</source> are equivalent.
<ol>
<li>
<code>null</code> is only ever equal to null, that is if you compare null
to any non-null value, the result is false.
</li>
<li>Equality uses the java <code>equals</code> method</li>
</ol>
</td>
</tr>
<tr>
<td>Inequality</td>
<td>
The usual <code>!=</code> operator can be used as well as the abbreviation <code>ne</code>.
For example
<source>val1 != val2</source> and
<source>val1 ne val2</source> are equivalent.
</td>
</tr>
<tr>
<td>Less Than</td>
<td>
The usual <code><</code> operator can be used as well as the abbreviation <code>lt</code>.
For example
<source>val1 < val2</source> and
<source>val1 lt val2</source> are equivalent.
</td>
</tr>
<tr>
<td>Less Than Or Equal To</td>
<td>
The usual <code><=</code> operator can be used as well as the abbreviation <code>le</code>.
For example
<source>val1 <= val2</source> and
<source>val1 le val2</source> are equivalent.
</td>
</tr>
<tr>
<td>Greater Than</td>
<td>
The usual <code>></code> operator can be used as well as the abbreviation <code>gt</code>.
For example
<source>val1 > val2</source> and
<source>val1 gt val2</source> are equivalent.
</td>
</tr>
<tr>
<td>Greater Than Or Equal To</td>
<td>
The usual <code>>=</code> operator can be used as well as the abbreviation <code>ge</code>.
For example
<source>val1 >= val2</source> and
<source>val1 ge val2</source> are equivalent.
</td>
</tr>
<tr>
<td>Addition</td>
<td>
The usual <code>+</code> operator is used.
For example
<source>val1 + val2</source>
</td>
</tr>
<tr>
<td>Subtraction</td>
<td>
The usual <code>-</code> operator is used.
For example
<source>val1 - val2</source>
</td>
</tr>
<tr>
<td>Multiplication</td>
<td>
The usual <code>*</code> operator is used.
For example
<source>val1 * val2</source>
</td>
</tr>
<tr>
<td>Division</td>
<td>
The usual <code>/</code> operator is used.
For example
<source>val1 / val2</source>
</td>
</tr>
<tr>
<td>Integer Division</td>
<td>
The <code>div</code> operator is used.
For example
<source>4 div 3</source> gives 1.
</td>
</tr>
<tr>
<td>Modulus (or remainder)</td>
<td>
The <code>%</code> operator is used. An alternative is the <code>mod</code>
operator.
For example
<source>5 mod 2</source> gives 1 and is equivalent to <source>5 % 2</source>
</td>
</tr>
<tr>
<td>Negation</td>
<td>
The unary <code>-</code> operator is used.
For example
<source>-12</source>
</td>
</tr>
<tr>
<td>Array access</td>
<td>
Array elements may be accessed using either square brackets or a dotted numeral, e.g.
<source>arr1[0]</source> and <source>arr1.0</source> are equivalent
</td>
</tr>
</table>
</section>
<section name="Conditional">
<table>
<tr><th width="15%">Operator</th><th>Description</th></tr>
<tr>
<td>if</td>
<td>
Classic, if/else statement, e.g.
<code>if ((x * 2) == 5) {y = 1;} else {y = 2;}</code>
</td>
</tr>
<tr>
<td>foreach</td>
<td>
Loop through items of an Array, Collection, Map, Iterator or Enumeration, e.g.
<code>foreach (item in list) { x = x + item; }</code>
Where <code>item</code> and <code>list</code> are variables.
</td>
</tr>
<tr>
<td>while</td>
<td>
Loop until a condition is satisfied, e.g.
<code>while (x lt 10) { x = x + 2; }</code>
</td>
</tr>
</table>
</section>
</body>
</document>
|
