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<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/viewvc/commons/proper/jexl/trunk/src/main/java/org/apache/commons/jexl2/parser/Parser.jjt?view=markup">Parser.jjt</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> or <code>//</code>and extend to the end of line, e.g.
            <source>## This is a comment</source>
            Also specified using <code>//</code>, e.g.
            <source>// This is a comment</source>
            Multiple lines comments are specified using <code>/*...*/</code>, e.g.
            <source>/* This is a
            multi-line 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>
            Variable names are <strong>case-sensitive</strong>, e.g. <code>var1</code> and <code>Var1</code> are different variables.
            </p>
            <p>
              <strong>NOTE:</strong> JEXL does not support variables with hyphens in them, e.g.
              <source>commons-logging // invalid variable name (hyphenated)</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>
            <p>
              JEXL also supports <code>ant-style</code> variables, the following is a valid variable name:
              <source>my.dotted.var</source>
            </p>
            <p>
              <strong>N.B.</strong> the following keywords are reserved, and cannot be used as a variable name or property when using the dot operator:
              <code>or and eq ne lt gt le ge div mod not null true false new var return</code>
              For example, the following is invalid:
              <source>my.new.dotted.var // invalid ('new' is keyword)</source>
              In such cases, quoted identifiers or the [ ] operator can be used, for example:
              <source>my.'new'.dotted.var</source>
              <source>my['new'].dotted.var</source>
            </p>
          </td>
        </tr>
        <tr>
          <td>Scripts</td>
          <td>
            <p>
            A script in Jexl is made up of zero or more statements. Scripts can be read from a String, File or URL.
            </p>
            <p>
            They can be created with named parameters which allow a later evaluation to be performed with arguments.
            </p>
            <p>
            A script returns the last expression evaluated by default.
            </p>
            <p>
            Using the <code>return</code> keyword, a script will return the expression that follows (or null).
            </p>
          </td>
        </tr>
        <tr>
          <td>Local variables</td>
          <td>Can be defined using the <code>var</code> keyword; their identifying rules are the same as contextual variables.
            <ul>
              <li>Basic declaration: <code>var x;</code></li>
              <li>Declaration with assignment: <code>var theAnswer = 42;</code></li>
              <li>Invalid declaration: <code>var x.y;</code></li>
            </ul>
            Their scope is the entire script scope and they take precedence in resolution over contextual variables.
            When scripts are created with named parameters, those behave as local variables.
            Local variables can not use <code>ant-style</code> naming, only one identifier.
          </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>
        <tr>
          <td>Assignment</td>
          <td>
            Assigns the value of a variable  (<code>my.var = 'a value'</code>) using a
            <code>JexlContext</code> as initial resolver. Both <em>beans</em> and <em>ant-ish</em>
            variables assignment are supported.
          </td>
        </tr>
        <tr>
          <td>Method calls</td>
          <td>
            Calls a method of an object, e.g.
            <source>"hello world".hashCode()</source> will call the <code>hashCode</code> method
            of the <code>"hello world"</code> String.
            <p>In case of multiple arguments and overloading, Jexl will make the best effort to find
            the most appropriate non ambiguous method to call.</p>
          </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>, eg <code>42</code>.
          </td>
        </tr>
        <tr>
          <td>Float 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>,
            optionally followed by <code>f</code> or <code>F</code>,
            eg <code>42.0</code> or <code>42.0f</code>.
          </td>
        </tr>
        <tr>
          <td>Long Literals</td>
          <td>1 or more digits from <code>0</code> to <code>9</code> suffixed with <code>l</code> or <code>L</code>
          , eg <code>42l</code>.
          </td>
        </tr>
        <tr>
          <td>Double 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> suffixed with <code>d</code> or <code>D</code>
            , eg <code>42.0d</code>.
          </td>
        </tr>
        <tr>
          <td>Big Integer Literals</td>
          <td>1 or more digits from <code>0</code> to <code>9</code> suffixed with <code>b</code> or <code>B</code>
          , eg <code>42B</code>.
          </td>
        </tr>
        <tr>
          <td>Big Decimal 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> suffixed with <code>h</code> or <code>H</code> (for Huge ala OGNL))
           , eg <code>42.0H</code>.
          </td>
        </tr>
        <tr>
          <td>Natural literals - octal and hex support</td>
          <td>
          Natural numbers (i.e. Integer, Long, BigInteger) can also be expressed as octal or hexadecimal using the same format as Java.
          i.e. prefix the number with <code>0</code> for octal, and prefix with <code>0x</code> or <code>0X</code> for hexadecimal.
          For example <code>010</code> or <code>0x10</code>.
          </td>
        </tr>
        <tr>
          <td>Real literals - exponent support</td>
          <td>
          Real numbers (i.e. Float, Double, BigDecimal) can also be expressed using standard Java exponent notation.
          i.e. suffix the number with <code>e</code> or <code>E</code> followed by the sign <code>+</code> or <code>-</code>
          followed by one or more decimal digits.
          For example <code>42.0E-1D</code> or <code>42.0E+3B</code>.
          </td>
        </tr>
        <tr>
          <td>String literals</td>
          <td>
            Can start and end with either <code>'</code> or <code>"</code> delimiters, e.g.
            <source>"Hello world"</source> and
            <source>'Hello world'</source> are equivalent.
            <p>The escape character is <code>\</code> (backslash); it only escapes the string delimiter</p>
          </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>
        <tr>
          <td>Array literal</td>
          <td>
            A <code>[</code> followed by one or more expressions separated by <code>,</code> and ending
            with <code>]</code>, e.g.
            <source>[ 1, 2, "three" ]</source>
            <p>This syntax creates an <code>Object[]</code>.</p>
            <p>
            JEXL will attempt to strongly type the array; if all entries are of the same class or if all
            entries are Number instance, the array literal will be an <code>MyClass[]</code> in the former
            case, a <code>Number[]</code> in the latter case.</p>
            <p>Furthermore, if all entries in the array literal are of the same class
            and that class has an equivalent primitive type, the array returned will be a primitive array. e.g.
            <code>[1, 2, 3]</code> will be interpreted as <code>int[]</code>.</p>
          </td>
        </tr>
        <tr>
          <td>Map literal</td>
          <td>
            A <code>{</code> followed by one or more sets of <code>key : value</code> pairs separated by <code>,</code> and ending
            with <code>}</code>, e.g.
            <source>{ "one" : 1, "two" : 2, "three" : 3, "more": "many more" }</source>
            <p>This syntax creates a <code>HashMap&lt;Object,Object&gt;</code>.</p>
          </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>
        <tr>
          <td>new</td>
          <td>
            Creates a new instance using a fully-qualified class name or Class:
            <source>new("java.lang.Double", 10)</source> returns 10.0.
            <p>Note that the first argument of <code>new</code> can be a variable or any
            expression evaluating as a String or Class; the rest of the arguments are used
            as arguments to the constructor for the class considered.</p>
            <p>In case of multiple constructors, Jexl will make the best effort to find
            the most appropriate non ambiguous constructor to call.</p>
          </td>
        </tr>
        <tr>
          <td>ns:function</td>
          <td>
            A <code>JexlEngine</code> can register objects or classes used as function namespaces.
            This can allow expressions like:
            <source>math:cosinus(23.0)</source>
          </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>&amp;&amp;</code> operator can be used as well as the word <code>and</code>, e.g.
            <source>cond1 and cond2</source> and
            <source>cond1 &amp;&amp; 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>&amp;</code> operator is used, e.g.
            <source>33 &amp; 4</source>, 0010 0001 &amp; 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>Ternary conditional <code>?:</code> </td>
          <td>
            The usual ternary conditional operator <code>condition ? if_true : if_false</code> operator can be
            used as well as the abbreviation <code>value ?: if_false</code> which returns the <code>value</code> if
            its evaluation is defined, non-null and non-false, e.g.
            <source>val1 ? val1 : val2</source> and
            <source>val1 ?: val2 </source> are equivalent.
            <p>
              <strong>NOTE:</strong> The condition will evaluate to <code>false</code> when it
              refers to an undefined variable or <code>null</code> for all <code>JexlEngine</code>
              flag combinations. This allows explicit syntactic leniency and treats the condition
              'if undefined or null or false' the same way in all cases.
            </p>
          </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>&lt;</code> operator can be used as well as the abbreviation <code>lt</code>.
            For example
            <source>val1 &lt; val2</source> and
            <source>val1 lt val2</source> are equivalent.
          </td>
        </tr>
        <tr>
          <td>Less Than Or Equal To</td>
          <td>
            The usual <code>&lt;=</code> operator can be used as well as the abbreviation <code>le</code>.
            For example
            <source>val1 &lt;= val2</source> and
            <source>val1 le val2</source> are equivalent.
          </td>
        </tr>
        <tr>
          <td>Greater Than</td>
          <td>
            The usual <code>&gt;</code> operator can be used as well as the abbreviation <code>gt</code>.
            For example
            <source>val1 &gt; val2</source> and
            <source>val1 gt val2</source> are equivalent.
          </td>
        </tr>
        <tr>
          <td>Greater Than Or Equal To</td>
          <td>
            The usual <code>&gt;=</code> operator can be used as well as the abbreviation <code>ge</code>.
            For example
            <source>val1 &gt;= val2</source> and
            <source>val1 ge val2</source> are equivalent.
          </td>
        </tr>
        <tr>
          <td>In or Match<code>=~</code></td>
          <td>
            The syntactically Perl inspired <code>=~</code> operator can be used to check that a <code>string</code> matches
            a regular expression (expressed either a Java String or a java.util.regex.Pattern).
            For example
            <code>"abcdef" =~ "abc.*</code> returns <code>true</code>.
            It also checks whether any collection, set or map (on keys) contains a value or not; in that case, it behaves
            as an "in" operator. Note that it also applies to arrays as well as "duck-typed" collection, ie classes exposing a "contains"
            method.
            <code> "a" =~ ["a","b","c","d","e",f"]</code> returns <code>true</code>.
          </td>
        </tr>
        <tr>
          <td>Not-In or Not-Match<code>!~</code></td>
          <td>
            The syntactically Perl inspired <code>!~</code> operator can be used to check that a <code>string</code> does not
            match a regular expression (expressed either a Java String or a java.util.regex.Pattern).
            For example
            <code>"abcdef" !~ "abc.*</code> returns <code>false</code>.
            It also checks whether any collection, set or map (on keys) does not contain a value; in that case, it behaves
            as "not in" operator. Note that it also applies to arrays as well as "duck-typed" collection, ie classes exposing a "contains"
            method.
            <code> "a" !~ ["a","b","c","d","e",f"]</code> returns <code>true</code>.
          </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, or one can use the <code>div</code> operator.
            For example
            <source>val1 / val2</source>
            or
            <source>val1 div val2</source>
          </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>
        <tr>
          <td>HashMap access</td>
          <td>
            Map elements are accessed using square brackets, e.g.
            <source>map[0]; map['name']; map[var];</source>
            Note that <source>map['7']</source> and <source>map[7]</source> refer to different elements.
            Map elements with a numeric key may also be accessed using a dotted numeral, e.g.
            <source>map[0]</source> and <source>map.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.
            <source>if ((x * 2) == 5) {
    y = 1;
} else {
    y = 2;
}</source>
          </td>
        </tr>
        <tr>
          <td>for</td>
          <td>
            Loop through items of an Array, Collection, Map, Iterator or Enumeration, e.g.
            <source>for(item : list) {
    x = x + item; 
}</source>
            Where <code>item</code> and <code>list</code> are variables.
            The JEXL 1.1 syntax using <code>foreach(item in list)</code> is now <strong>deprecated</strong>.
          </td>
        </tr>
        <tr>
          <td>while</td>
          <td>
            Loop until a condition is satisfied, e.g.
            <source>while (x lt 10) {
    x = x + 2; 
}</source>
          </td>
        </tr>
      </table>
    </section>

  </body>
</document>

