Spring Expression Language docs
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Mark Pollack
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@ -72,7 +72,7 @@
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</listitem>
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<listitem>
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<para>Operators</para>
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<para>Relational operators</para>
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</listitem>
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<listitem>
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@ -83,6 +83,10 @@
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<para>Calling constructors</para>
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</listitem>
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<listitem>
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<para>Ternary operator</para>
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</listitem>
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<listitem>
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<para>Variables</para>
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</listitem>
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@ -429,49 +433,189 @@ String city = (String) parser.parseExpression("placeOfBirth.City").getValue(cont
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names. The contents of arrays and lists are obtained using square
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bracket notation. </para>
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<programlisting></programlisting>
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<programlisting language="java">ExpressionParser parser = new SpelAntlrExpressionParser();
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// Inventions Array
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StandardEvaluationContext teslaContext = new StandardEvaluationContext();
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teslaContext.setRootObject(tesla);
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// evaluates to "Induction motor"
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String invention = parser.parseExpression("inventions[3]").getValue(teslaContext, String.class);
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// Members List
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StandardEvaluationContext societyContext = new StandardEvaluationContext();
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societyContext.setRootObject(ieee);
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// evaluates to "Nikola Tesla"
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String name = parser.parseExpression("Members[0].Name").getValue(societyContext, String.class);
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// List and Array navigation
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// evaluates to "Wireless communication"
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String invention = parser.parseExpression("Members[0].Inventions[6]").getValue(societyContext, String.class);
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</programlisting>
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<para>The contents of dictionaries are obtained by specifying the
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literal key value within the brackets. In this case, because keys for
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the Officers dictionary are strings, we can specify string
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literal.</para>
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<programlisting lang="" language="java">// Officer's Dictionary
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Inventor pupin = parser.parseExpression("Officers['president']").getValue(societyContext, Inventor.class);
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// evaluates to "Idvor"
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String city = parser.parseExpression("Officers['president'].PlaceOfBirth.City").getValue(societyContext, String.class);
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// setting values
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parser.parseExpression("Officers['advisors'][0].PlaceOfBirth.Country").setValue(societyContext, "Croatia");
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</programlisting>
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</section>
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<section>
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<title>Methods</title>
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<para>blah blah varargs</para>
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<para>Methods are invoked using typical Java programming syntax. You may
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also invoke methods on literals. Varargs are also supported.</para>
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<programlisting language="java">// string literal, evaluates to "bc"
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String c = parser.parseExpression("'abc'.substring(2, 3)").getValue(String.class);
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// evaluates to true
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boolean isMember = parser.parseExpression("isMember('Mihajlo Pupin')").getValue(societyContext, Boolean.class);</programlisting>
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</section>
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<section>
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<title>Operators</title>
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<para>blah blah</para>
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<section>
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<title>Relational operators</title>
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<para>blah blah</para>
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<para>The relational operators; equal, not equal, less than, less than
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or equal, greater than, and greater than or equal are supported using
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standard operator notation. Support is not yet implemented for objects
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that implement the Comparable interface.</para>
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<para></para>
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<para><programlisting language="java">// evaluats to true
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boolean isEqual = parser.parseExpression("2 == 2").getValue(Boolean.class);
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// evaluates to false
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boolean isEqual = parser.parseExpression("2 < -5.0").getValue(Boolean.class);
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// evaluates to true
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boolean isEqual = parser.parseExpression("'black' < 'block'").getValue(Boolean.class);</programlisting>In
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addition to standard relational operators SpEL supports the
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'instanceof' and regular expression based 'matches' operator.</para>
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<programlisting language="java">// evaluates to false
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boolean falseValue = parser.parseExpression("'xyz' instanceof T(int)").getValue(Boolean.class);
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// evaluates to true
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boolean trueValue = parser.parseExpression("'5.00' matches '^-?\\d+(\\.\\d{2})?$'").getValue(Boolean.class);
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//evaluates to false
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boolean falseValue = parser.parseExpression("'5.0067' matches '^-?\\d+(\\.\\d{2})?$'").getValue(Boolean.class);
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</programlisting>
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</section>
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<section>
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<title>Logical operators</title>
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<para></para>
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<para>The logical operators that are supported are and, or, and not.
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Their use is demonstrated below</para>
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<para></para>
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<para><programlisting language="java">// -- AND --
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// evaluates to false
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boolean falseValue = parser.parseExpression("true and false").getValue(Boolean.class);
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// evaluates to true
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String expression = "isMember('Nikola Tesla') and isMember('Mihajlo Pupin')";
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boolean trueValue = parser.parseExpression(expression).getValue(societyContext, Boolean.class);
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// -- OR --
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// evaluates to false
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boolean falseValue = parser.parseExpression("true or false").getValue(Boolean.class);
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// evaluates to true
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String expression = "isMember('Nikola Tesla') or isMember('Albert Einstien')";
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boolean trueValue = parser.parseExpression(expression).getValue(societyContext, Boolean.class);
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// -- NOT --
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// evaluates to false
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boolean falseValue = parser.parseExpression("!true").getValue(Boolean.class);
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// -- AND and NOT --
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String expression = "isMember('Nikola Tesla') and !isMember('Mihajlo Pupin')";
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boolean falseValue = parser.parseExpression(expression).getValue(societyContext, Boolean.class);</programlisting></para>
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</section>
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<section>
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<title>Mathematical operators</title>
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<para>blah blah</para>
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<para>The addition operator can be used on numbers, strings and dates.
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Subtraction can be used on numbers and dates. Multiplication and
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division can be used only on numbers. Other mathematical operators
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supported are modulus (%) and exponential power (^). Standard operator
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precedence is enforced. These operators are demonstrated below </para>
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<para></para>
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<para><programlisting>// Addition
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int two = parser.parseExpression("1 + 1").getValue(Integer.class); // 2
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String testString = parser.parseExpression("'test' + ' ' + 'string'").getValue(String.class); // 'test string'
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// Subtraction
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int four = parser.parseExpression("1 - -3").getValue(Integer.class); // 4
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double d = parser.parseExpression("1000.00 - 1e4").getValue(Double.class); // -9000
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// Multiplication
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int six = parser.parseExpression("-2 * -3").getValue(Integer.class); // 6
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double twentyFour = parser.parseExpression("2.0 * 3e0 * 4").getValue(Double.class); // 24.0
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// Division
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int minusTwo = parser.parseExpression("6 / -3").getValue(Integer.class); // -2
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double one = parser.parseExpression("8.0 / 4e0 / 2").getValue(Double.class); // 1.0
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// Modulus
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int three = parser.parseExpression("7 % 4").getValue(Integer.class); // 3
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int one = parser.parseExpression("8 / 5 % 2").getValue(Integer.class); // 1
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// Operator precedence
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int minusTwentyOne = parser.parseExpression("1+2-3*8").getValue(Integer.class); // -21
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</programlisting></para>
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</section>
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</section>
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<section>
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<title>Assignment</title>
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<para>blah blah</para>
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<para>Setting of a property is done by using the assignment operator.
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This would typically be done within a call to SetValue but can also be
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done inside a call to GetValue </para>
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<programlisting>Inventor inventor = new Inventor();
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StandardEvaluationContext inventorContext = new StandardEvaluationContext();
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inventorContext.setRootObject(inventor);
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parser.parseExpression("Name").setValue(inventorContext, "Alexander Seovic2");
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// alternatively
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String aleks = parser.parseExpression("Name = 'Alexandar Seovic'").getValue(inventorContext, String.class);
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</programlisting>
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<para></para>
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</section>
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@ -479,19 +623,47 @@ String city = (String) parser.parseExpression("placeOfBirth.City").getValue(cont
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<section>
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<title>Types</title>
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<para>blah blah</para>
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<para>The specic 'T' operator can be used to specify an instance of
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java.lang.Class (the 'type'). Static methods are invoked using this
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operator as well</para>
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<programlisting>Class dateClass = parser.parseExpression("T(java.util.Date)").getValue(Class.class);
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boolean isEqual = parser.parseExpression("T(java.math.RoundingMode).CEILING < T(java.math.RoundingMode).FLOOR").getValue(Boolean.class);
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</programlisting>
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</section>
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<section>
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<title>Constructors</title>
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<para>blah blah</para>
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<para>Constructors can be invoked using the new operator. The fully
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qualified classname should be used for all but the primitive type and
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String (where int, float, etc, can be used).</para>
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<programlisting>Inventor einstein =
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parser.parseExpression("new org.spring.samples.spel.inventor.Inventor('Albert Einstein', 'German')").getValue(Inventor.class);
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//create new inventor instance within add method of List
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parser.parseExpression("Members.add(new org.spring.samples.spel.inventor.Inventor('Albert Einstein', 'German'))").getValue(societyContext);
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</programlisting>
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</section>
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<section id="expressions-ref-variables">
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<title>Variables</title>
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<para>blah blah</para>
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<para>Variables can referenced in the expression using the syntax
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#variableName. Variables are set using the method setVariable on the
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StandardEvaluationContext. </para>
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<programlisting>Inventor tesla = new Inventor("Nikola Tesla", "Serbian");
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StandardEvaluationContext context = new StandardEvaluationContext();
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context.setVariable("newName", "Mike Tesla");
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context.setRootObject(tesla);
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parser.parseExpression("Name = #newName").getValue(context);
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System.out.println(tesla.getName()) // "Mike Tesla"</programlisting>
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<section>
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<title>The #this and #root variables</title>
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@ -506,6 +678,42 @@ String city = (String) parser.parseExpression("placeOfBirth.City").getValue(cont
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<para>blah blah</para>
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</section>
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<section>
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<title>Ternary Operator (If-Then-Else)</title>
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<para>You can use the ternary operator for performing if-then-else
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conditional logic inside the expression. A minimal example is; </para>
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<programlisting language="java">String falseString = parser.parseExpression("false ? 'trueExp' : 'falseExp'").getValue(String.class);</programlisting>
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<para>In this case, the boolean false results in returning the string
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value 'falseExp'. A less artificial example is shown below.</para>
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<programlisting>parser.parseExpression("Name").setValue(societyContext, "IEEE");
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societyContext.setVariable("queryName", "Nikola Tesla");
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expression = "isMember(#queryName)? #queryName + ' is a member of the ' " +
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"+ Name + ' Society' : #queryName + ' is not a member of the ' + Name + ' Society'";
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String queryResultString = parser.parseExpression(expression).getValue(societyContext, String.class);</programlisting>
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</section>
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<section>
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<title>List Selection</title>
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<para>List selection is a powerful expression language feature that
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allow you to transform the source list into another list by selecting
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from its "rows". In other words, selection is comparable to using SQL
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with a WHERE clause.</para>
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<para>Selection uses the syntax ?{projectionExpression}. This will
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filter the list and return a new list containing a subset of the
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original element list. For example, selection would allow us to easily
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get a list of Serbian inventors:</para>
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<programlisting>List<Inventor> list = (List<Inventor>) parser.parseExpression("Members.?{Nationality == 'Serbian'}").getValue(societyContext);</programlisting>
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</section>
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<section>
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<title>Expression templating</title>
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