This version is still in development and is not considered stable yet. For the latest stable version, please use Spring Framework 6.2.4! |
The Elvis Operator
The Elvis operator (?:
) is a shortening of the ternary operator syntax and is used in
the Groovy language. With the
ternary operator syntax, you often have to repeat a variable twice, as the following Java
example shows:
String name = "Elvis Presley";
String displayName = (name != null ? name : "Unknown");
Instead, you can use the Elvis operator (named for the resemblance to Elvis' hair style). The following example shows how to use the Elvis operator in a SpEL expression:
-
Java
-
Kotlin
ExpressionParser parser = new SpelExpressionParser();
String name = parser.parseExpression("name ?: 'Unknown'").getValue(new Inventor(), String.class);
System.out.println(name); // 'Unknown'
val parser = SpelExpressionParser()
val name = parser.parseExpression("name ?: 'Unknown'").getValue(Inventor(), String::class.java)
println(name) // 'Unknown'
The SpEL Elvis operator also treats an empty String like a |
As of Spring Framework 7.0, the SpEL Elvis operator supports For example, given the expression |
The following listing shows a more complex example:
-
Java
-
Kotlin
ExpressionParser parser = new SpelExpressionParser();
EvaluationContext context = SimpleEvaluationContext.forReadOnlyDataBinding().build();
Inventor tesla = new Inventor("Nikola Tesla", "Serbian");
String name = parser.parseExpression("name ?: 'Elvis Presley'").getValue(context, tesla, String.class);
System.out.println(name); // Nikola Tesla
tesla.setName("");
name = parser.parseExpression("name ?: 'Elvis Presley'").getValue(context, tesla, String.class);
System.out.println(name); // Elvis Presley
val parser = SpelExpressionParser()
val context = SimpleEvaluationContext.forReadOnlyDataBinding().build()
val tesla = Inventor("Nikola Tesla", "Serbian")
var name = parser.parseExpression("name ?: 'Elvis Presley'").getValue(context, tesla, String::class.java)
println(name) // Nikola Tesla
tesla.setName("")
name = parser.parseExpression("name ?: 'Elvis Presley'").getValue(context, tesla, String::class.java)
println(name) // Elvis Presley
You can use the Elvis operator to apply default values in expressions. The following
example shows how to use the Elvis operator in a
This will inject the value of the system property named |