This version is still in development and is not considered stable yet. For the latest stable version, please use Spring Framework 6.1.9!

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 usually have to repeat a variable twice, as the following 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:

  • 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 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(null);
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(null)
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 @Value expression:

@Value("#{systemProperties['pop3.port'] ?: 25}")

This will inject a system property pop3.port if it is defined or 25 if not.