SpEL introduction

Spring SpEL is used to parse expressions through your @Value or even standalone. Another thing that you should keep in mind is that your expressions can be evaluated in runtime or you can ask SpEL to work in the compile mode to increase performance, although you will lose functionalities if you do that.

With SpEL you can also access beans and call methods inside of it. Let’s take the example below:

ExpressionParser parser = new SpelExpressionParser();
System.out.println(parser.parseExpression("new String('Name to upper').toUpperCase()").getValue());

You could also access your beans through the Spel like below:

        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(ApplicationConfiguration.class);

        StandardEvaluationContext evaluationContext = new StandardEvaluationContext();
        evaluationContext.setBeanResolver(new BeanFactoryResolver(context));

        ExpressionParser parser = new SpelExpressionParser();

        System.out.println(
                parser.parseExpression("@beanOne.firstName").getValue(evaluationContext)
        );
        System.out.println(
                parser.parseExpression("@beanOne.amountAvailable * 2").getValue(evaluationContext)
        );
        

SpEL examples

• Static Fields > T(com.spring.example.Item).DEFAULT_CODE
• Static Methods > T(com.spring.example.Item).getDefaultCode()
• Spring Bean Property > @beanOne.itemCode
• Spring bean Method > @beanOne.getItemCode()
• Variables > #personName
• Object property assigned to SpEL variables > #person.name
• Object method assigned to SpEL variables > person.getName()
• Environment Properties > environment[‘app.item.default.code.property’]
• System Properties > systemProperties[‘app.vm.property’]
• System Environment Properties > systemEnvironment[‘JAVA_HOME’]