Variables
You can reference variables in the expression by using the #variableName
syntax. Variables
are set by using the setVariable
method on EvaluationContext
implementations.
Valid variable names must be composed of one or more of the following supported characters.
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The following example shows how to use variables.
-
Java
-
Kotlin
Inventor tesla = new Inventor("Nikola Tesla", "Serbian");
EvaluationContext context = SimpleEvaluationContext.forReadWriteDataBinding().build();
context.setVariable("newName", "Mike Tesla");
parser.parseExpression("name = #newName").getValue(context, tesla);
System.out.println(tesla.getName()) // "Mike Tesla"
val tesla = Inventor("Nikola Tesla", "Serbian")
val context = SimpleEvaluationContext.forReadWriteDataBinding().build()
context.setVariable("newName", "Mike Tesla")
parser.parseExpression("name = #newName").getValue(context, tesla)
println(tesla.name) // "Mike Tesla"
The #this
and #root
Variables
The #this
variable is always defined and refers to the current evaluation object
(against which unqualified references are resolved). The #root
variable is always
defined and refers to the root context object. Although #this
may vary as components of
an expression are evaluated, #root
always refers to the root. The following examples
show how to use the #this
and #root
variables:
-
Java
-
Kotlin
// create an array of integers
List<Integer> primes = new ArrayList<>();
primes.addAll(Arrays.asList(2,3,5,7,11,13,17));
// create parser and set variable 'primes' as the array of integers
ExpressionParser parser = new SpelExpressionParser();
EvaluationContext context = SimpleEvaluationContext.forReadOnlyDataAccess();
context.setVariable("primes", primes);
// all prime numbers > 10 from the list (using selection ?{...})
// evaluates to [11, 13, 17]
List<Integer> primesGreaterThanTen = (List<Integer>) parser.parseExpression(
"#primes.?[#this>10]").getValue(context);
// create an array of integers
val primes = ArrayList<Int>()
primes.addAll(listOf(2, 3, 5, 7, 11, 13, 17))
// create parser and set variable 'primes' as the array of integers
val parser = SpelExpressionParser()
val context = SimpleEvaluationContext.forReadOnlyDataAccess()
context.setVariable("primes", primes)
// all prime numbers > 10 from the list (using selection ?{...})
// evaluates to [11, 13, 17]
val primesGreaterThanTen = parser.parseExpression(
"#primes.?[#this>10]").getValue(context) as List<Int>