What is Spring Expression Language?

Spring Expression Language is just expression language in Spring. Supported since spring 3.0.

Several way to Expression Spel, first write in ‘#{}’ literal.

  1. Plus Integer.
  2. Plus String.
  3. Expression Boolean.
  4. Get property (using ‘${ }’ literal).
  5. Get Bean.
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    @Component
    public class SpelRunner implements ApplicationRunner {

        @Value("#{1 + 1}") //Plus Integer.
        int value;

        @Value("#{'hello ' + 'world'}") //Plus String.
        String greeting;

        @Value("#{1 eq 1}") //Expression Boolean.
        boolean trueOrFalse;

        @Value("${my.value}")   //Get property.
        int myValue;

        @Value("#{${my.value} eq 100}") //Expression Boolean of get property.
        boolean isMyValue;

        @Value("#{'spring'}")   //Expression just string
        String spring;

        @Value("#{sample.data}")    //Get Bean.
        int sampleData;

        @Override
        public void run(ApplicationArguments args) throws Exception {
            System.out.println("=============");
            System.out.println(value);
            System.out.println(greeting);
            System.out.println(trueOrFalse);
            System.out.println(myValue);
            System.out.println(isMyValue);
            System.out.println(spring);
            System.out.println(sampleData);
        }
    }

Actually used

  • Value annotation
  • @ConditionalOnExpression annotation
  • Spring Security
  • Spring Data (@Query annotation)
  • Thymeleaf