spring expression language example

spring-el.java

@Autowired
private Employee firstEmployee;

/*
  name
  #this.toString()
  roles.?[level>7].![id]
	roles.?[id>0].toString()
	roles.![roleName]
  roles.![{role_name:roleName,id:id}].toString()
  #{ T(java.lang.Math).random() * 100.0 }
  #{ T(java.lang.System).getenv().toString() }
 */
	@Override
	public void run(ApplicationArguments args) throws Exception {
		System.out.println(Arrays.toString(args.getSourceArgs()));
		System.out.println(firstEmployee.toString());

		ExpressionParser expressionParser = new SpelExpressionParser();
		SimpleEvaluationContext context = SimpleEvaluationContext
				.forReadOnlyDataBinding()
				.withInstanceMethods()
				.build();

		Scanner scanner = new Scanner(System.in);
		while(true) {
			try {
				String line = scanner.nextLine();
				Expression expression = expressionParser.parseExpression(line);
				System.out.println(expression.getValue(context, firstEmployee, String.class));
			} catch (Exception e) {
				System.err.println("expression evaluation failed");
			}
		}
	}

	@Bean
	@Qualifier("firstEmployee")
	public Employee firstEmployee() {
		return Employee.builder()
				.id(nextLong())
				.name(random(6, "abc"))
				.roles(Arrays.asList(
						Role.builder().id(nextLong(1000, 10000)).level(nextInt(1,11)).roleName(random(3, "xyz")).build(),
						Role.builder().id(nextLong(1000, 10000)).level(nextInt(1,11)).roleName(random(3, "xyz")).build(),
						Role.builder().id(nextLong(1000, 10000)).level(nextInt(1,11)).roleName(random(3, "xyz")).build(),
						Role.builder().id(nextLong(1000, 10000)).level(nextInt(1,11)).roleName(random(3, "xyz")).build(),
						Role.builder().id(nextLong(1000, 10000)).level(nextInt(1,11)).roleName(random(3, "xyz")).build()
						))
				.build();
	}