SPEL in a nutshell

spel-in-a-nutshell.md

class RootObject {
  private String prop;
  private Child child;
}

// with root object
JavaExpressionParser expressionParser = new SpelExpressionParser();
Expression expression = expressionParser.parseExpression("prop + #var + 'somethingelse'");
RootObject rootObject = new RootObject("whatever");
EvaluationContext context = new StandardEvaluationContext(rootObject);
context.setVariable("var", "var val");
String result = expression.getValue(context, String.class);

Basics

• @Value("#{...}") - Basic format for property binding in Spring, which comes from StandardBeanExpressionResolver which has expressionPrefix as #{ & sufix as }

Within the expressions (#{...here...})

• T(fqcn.MyClass).staticMethod(..) - For accessing java Class object
• @myBeanRef.prop - For accessing beans from application context if context is configured with a custom BeanResolver via context.setBeanResolver(new MyBeanResolver());
• #0, #methodParam, #customVar - Variables set via context.setVariable("0", "val") format can be accessed using # within
• child.prop") - Accessing child of rootObject set within evaluation context
• obj?.nullableProp?.deeperNullableProp") - Null safe navigation
• booleanVar ?: 'Hello'") - Elvis operator supported
• collection[1]") - Index based collection element access
• map['key']") - Access map value based on Key
• obj.method('val')") - Method execution against the child
• methodOnRoot('val')") - Method execution against root object
• ${custom.property}") - Access environment properties in spring