This version is still in development and is not considered stable yet. For the latest stable version, please use Spring Framework 6.0.26! |
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:
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Java
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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:
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Java
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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
This will inject a system property |