Jakarta Expression Language

Jakarta Expression Language 6.0 removes the dependency on SecurityManager and several deprecated APIs. It also introduces a number of notable improvements for developers:

• Arrays now support a new length property.
• Introduces support for java.lang.Record through the new RecordELResolver, which is enabled by default.
• Adds support for java.lang.Optional via the new OptionalELResolver, which is disabled by default.

Let's use an example to explain these.

public record Customer(
        String firstName,
        String lastName,
        Optional<PhoneNumber> phoneNumber,
        EmailAddress[] emailAddresses,
        Address address
) {
}

record PhoneNumber(String countryCode, String number) {
}

record EmailAddress(
        String email,
        Boolean primary
) {
}

record Address(
        String street,
        String city,
        String state,
        String zipCode
) {
}

In a Java SE environment, you can initialize an ELProcessor and evaluate expressions as follows::

var elProcessor = new ELProcessor();

// add OptionalELResolver to support Optional
elProcessor.getELManager().addELResolver(new OptionalELResolver());

elProcessor.defineBean("customer", new Customer(
                        "Foo",
                        "Bar",
                        Optional.of(new PhoneNumber("001", "3334445555")),
                        new EmailAddress[]{
                                new EmailAddress("foo@example.com", true),
                                new EmailAddress("bar@example.com", false)
                        },
                        new Address("123 Main St", "Anytown", "CA", "12345")
                )
        );

// access optional phonenumber
// String phoneNumber = elProcessor.eval("customer.phoneNumber.map(p-> '('.concat(p.countryCode).concat(')').concat(p.number)).orElse('NotFound')");
String phoneNumber = elProcessor.eval("'('.concat(customer.phoneNumber.countryCode).concat(')').concat(customer.phoneNumber.number)");
System.out.println(phoneNumber);

String firstName = elProcessor.eval("customer.firstName");
String lastName = elProcessor.eval("customer.lastName");
System.out.println(firstName);
System.out.println(lastName);

Integer emailLength = elProcessor.eval("customer.emailAddresses.length");
System.out.println("email length = " + emailLength);

// access email
String email = elProcessor.eval("customer.emailAddresses[0].email");
System.out.println("email = " + email);

// access address
String street = elProcessor.eval("customer.address.street");
System.out.println("street = " + street);

String state = elProcessor.eval("customer.address.state");
System.out.println("state = " + state);

String city = elProcessor.eval("customer.address.city");
System.out.println("city = " + city);

String zip = elProcessor.eval("customer.address.zipCode");
System.out.println("zip = " + zip);

In the above code, we use expression customer.phoneNumber.countryCode and customer.phoneNumber.number to access the countryCode and number properties of the PhoneNumber record, which is wrapped in an Optional. The OptionalELResolver allows us to access these properties directly without needing to check if the Optional is present or not.

If the customer.phoneNumber is Optional.empty(), the expression will evaluate to null instead of throwing an exception, which is a significant improvement in handling optional values in expressions.

The expression customer.emailAddresses.length demonstrates the new length property for arrays, which returns the length of the emailAddresses array.

The expressions customer.firstName, customer.lastName, customer.address.street, customer.address.state, customer.address.city, and customer.address.zipCode show how to access properties of the Customer record and its nested Address record using the new RecordELResolver.

Check the full example code on Github and explore if yourself.