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1. Introduction to Hawaii

The Hawaii Framework is a Java framework for developing Spring based applications.

It provides production-ready features and integrations based best practices and experience to boost projects.

The Hawaii Framework is developed internally at QNH and is used in projects for medium and large enterprise customers.

1.1. Spring Boot

Combining Spring Boot and the Hawaii production-ready features and auto configuration brings even more power and simplicity to developers, without sacrificing flexibility.

The Hawaii Framework also provides various Spring Boot Starters to automatically include the needed dependencies and trigger the auto configuration of the Hawaii production-ready features.

But it is important to mention that most of the Hawaii features can also used without using Spring Boot. In that case the desired features need to be configured manually by defining the appropriate Spring beans inside the application’s context.

2. Getting Started with Hawaii


3. Hawaii Features


3.3. Logging


3.4. Hawaii Time

HawaiiTime is not merely a convenient wrapper to instantiate new java.time date and time objects. It provides an application wide java.time.Clock reference which is particular useful for unit testing.

It is similar to Joda’s DateTimeUtils which also allows setting a fixed current time. However it is important to note that Joda’s DateTimeUtils uses a static variable to store the current time. HawaiiTime does not take this approach. Instead the HawaiiTime bean needs to be injected in any class that needs to instantiate new date and time objects. This approach is more flexible and e.g. has the benefit that unit tests can be run in parallel. See example usage below.

public class MyClass {

	private HawaiiTime hawaiiTime;

	public MyClass(HawaiiTime hawaiiTime) { (1)
		this.hawaiiTime = hawaiiTime;

	public void doSomethingWithDate() {
		ZonedDateTime dateTime = this.hawaiiTime.zonedDateTime(); (2)
		// ...

public class MyClassTests {

	public void testDoSomethingWithDate() {
	    long millis = System.currentTimeMillis();
		HawaiiTime hawaiiTime = new HawaiiTime();
		hawaiiTime.useFixedClock(millis); (3)
		MyClass myClass = new MyClass(hawaiiTime);
		// ...
1 Inject the HawaiiTime bean.
2 Use the injected HawaiiTime bean to instantiate new date and time objects.
3 In unit tests a fixed clock can be used to manipulate and predict the exact current time.

Another benefit of using HawaiiTime is that a fixed time can be used in a running application to test how it behaves on a given date or time.

Third-party libraries being used by the application do not use HawaiiTime and probably instantiate date and time objects based on the System time.

Hawaii uses UTC as default timezone but this can be changed by setting the hawaii.time.timezone configuration property. The provided value will be parsed by java.time.ZoneId#of(String zoneId) and supports different timezone formats like UTC, Europe/Amsterdam and GMT+1.

The creation of the HawaiiTime bean can also be disabled by setting hawaii.time.enabled to false.

3.5. Validation

Hawaii’s validation mechanism can be used to validate any object. It basically validates values, collects validation errors and stores them in a validation result. These validation errors are simple field / error code combinations.

Hawaii’s Validator is inspired on Spring’s org.springframework.validation.Validator mechanism. However Hawaii’s validator mechanism uses it’s own ValidationResult instead of Spring’s org.springframework.validation.Errors. The main difference is that Hawaii’s ValidationResult does not bind directly the object being validated. This also gives the possibility to add errors for specific keys that are not direct properties of the object being validated.

Hawaii’s validation mechanism also provides additional sugar like Hamcrest matcher support to write human readable validating code, the capability to validate and automatically throw a ValidationException in case of errors etc.

Like Spring’s validation mechanism the Hawaii validation mechanism also supports the notion of nested error paths which also stimulates to re-use validators.

Let’s take an example. Imagine a Customer object with common name, e-mail, and address fields. A validation result could for example contain the following field / error code combinations:

first_name = required (1)
last_name = max_length_exceeded
email = invalid
addresses = primary_address_required (2)
addresses[0].type = invalid (3)
addresses[0].street_name = max_length_exceeded
addresses[0].postal_code = invalid
addresses[0].city = max_length_exceeded
addresses[0].country_code = required
1 The field first_name has an required error code.
2 The field adresses (an array in this case) has primary_address_required error code.
3 The field type of the first address in the addresses array has a invalid error code.

The example demonstrates simple field errors (like first_name) but also storing errors for arrays and nested paths (addresses[0].type). In theory a field could also have multiple error codes if needed.

Implementors should typically only implement the org.hawaiiframework.sample.validator.Validator#validate(Object, ValidationResult) method as the other methods in the interface are already implemented using the interface’s default methods.

A generic EmailValidator would look like:

import org.hawaiiframework.validation.ValidationResult;
import org.hawaiiframework.validation.Validator;
import org.springframework.stereotype.Component;

import java.util.regex.Pattern;

public class EmailValidator implements Validator<String> { (1)

    public static final String EMAIL_PATTERN = "^[_A-Za-z0-9-\\+]+(\\.[_A-Za-z0-9-]+)*@[A-Za-z0-9-]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$";

    private Pattern pattern;

    public EmailValidator() {
        this.pattern = Pattern.compile(EMAIL_PATTERN);

    public void validate(String email, ValidationResult validationResult) { (2)
        if (!pattern.matcher(email).matches()) {
            validationResult.rejectValue("invalid"); (3)
1 Implement the Validator (in this case a String).
2 Override the Validator#validate(Object, ValidationResult) method.
3 In case the e-mail is invalid, reject the value with error code invalid and store it in the validation result.

The CustomerValidator would look like:

import org.apache.commons.lang3.StringUtils;
import org.hawaiiframework.sample.validator.EmailValidator;
import org.hawaiiframework.validation.ValidationResult;
import org.hawaiiframework.validation.Validator;
import org.springframework.stereotype.Component;

import java.util.List;

import static org.hamcrest.Matchers.greaterThan;

public class CustomerInputValidator implements Validator<CustomerInput> { (1)

    private final EmailValidator emailValidator;
    private final AddressValidator addressValidator;

    public CustomerInputValidator(final EmailValidator emailValidator,
            final AddressValidator addressValidator) { (2)
        this.emailValidator = emailValidator;
        this.addressValidator = addressValidator;

    public void validate(CustomerInput customer, ValidationResult validationResult) { (3)

        // first name validation
        String firstName = customer.getFirstName();
        if (StringUtils.isBlank(firstName)) {
            validationResult.rejectValue("first_name", "required");
        } else {
            validationResult.rejectValueIf(firstName.length(), greaterThan(25), "first_name",

        // last name validation
        String lastName = customer.getLastName();
        if (StringUtils.isBlank(lastName)) {
            validationResult.rejectValue("last_name", "required");
        } else {
            validationResult.rejectValueIf(lastName.length(), greaterThan(25), "last_name",

        // e-mail validation
        String email = customer.getEmail();
        if (StringUtils.isBlank(email)) {
            validationResult.rejectValue("email", "required");
        } else if (email.length() > 100) {
            validationResult.rejectValue("email", "max_length_exceeded");
        } else {
            emailValidator.validate(email, validationResult);

        // adresses validation
        List<Address> addresses = customer.getAddresses();
        if (addresses == null || addresses.size() == 0) {
            validationResult.rejectValue("addresses", "required");
        } else {
            // addresses array validations
            long primaries = addresses.stream()
                    .filter(address -> address.getType() == AddressType.PRIMARY)
            if (primaries == 0) {
                validationResult.rejectValue("addresses", "primary_address_required");
            } else if (primaries > 1) {
                validationResult.rejectValue("addresses", "only_1_primary_address_allowed");
            if (addresses.size() > 3) {
                validationResult.rejectValue("addresses", "max_array_length_exceeded");
            // address validations
            for (int i = 0; i < addresses.size(); i++) {
                validationResult.pushNestedPath("addresses", i);
                addressValidator.validate(addresses.get(i), validationResult);
1 Implement the Validator (in this case a Customer).
2 Inject other validators (EmailValidator, AddressValidator) to be re-used.
3 Override the Validator#validate(Object, ValidationResult) method.

4. Hawaii Starters


4.4. hawaii-starter-async

The asynchronous request execution in Hawaii is built on top of the scheduling in Spring Framework, see the Spring documentation for a baseline explanation.

There are two main additions:

  • More flexibility in executor configuration

  • Task timeout

4.4.1. Executor configuration

The Hawaii async configuration allows the definition of executors. An executor can be viewed as a thread pool. An executor configuration looks something like this:

    name: default
    corePoolSize: 10
    keepAliveTime: 60
    maxPendingRequests: 60
    maxPoolSize: 60

The lowest level of configuration is a task. Tasks are grouped into systems. A system could be some backend system against which requests are executed, or a database on which queries are executed. Each request or query represents a task in Hawaii async terminology. System and task configuration looks like this:

      name: mySystem
      defaultExecutor: myExecutor
      defaultTimeout: 3
            method: myTask
            executor: mySpecialExecutor
            timeout: 1
            method: myOtherTask

As can be seen, an executor can be assigned on system level. This will be the default executor for all the tasks in the system, unless a specific executor is configured for a task, such as myTask in the example. The same mechanism applies to the timeout settings. It is therefore perfectly legal to configure a task without any properties. However, it remains necessary to define the task in the configuration, otherwise it can’t be used, i.e. every task must be defined in the configuration.

Finally, there are some global properties:

defaultExecutor: default
defaultTimeout: 10
asyncTimeoutExecutorPoolSize: 10

These define the default executor and timeout. These defaults will be used if no executor or timeout is defined on either task or system.

The asyncTimeoutExecutorPoolSize property defines the number of threads that are used to run timeout tasks. See task timeout.

4.4.2. Task timeout

Another addition is automatically timing out tasks. For each task that is executed, the Hawaii async framework enqueues a cancellation task into a separate executor. If the timeout moment arrives, the timeout task is executed and will attempt to abort the actual task being executed. The actual task will remove the timeout task when it finishes, so if a task runs within its time limit, the timeout task will never be run.

4.4.3. Usage

In practice, using the Hawaii asynchronous framework is not that different from using Spring’s: asynchronous execution must be enabled with @EnableAsync and methods that are to be executed asynchronously must be annotated with the @Async annotation, and they must have a Future typed return value.

Additionally, an asynchronous configuration must be defined in the file identified by the hawaii.async.configuration property, which is set to ./config/async-config.yml by default.

The essential difference in usage is that where Spring allows the specification of an executor by specifying the value of the @Async annotation, the Hawaii additions allow specifying the Task name instead of the executor. The Hawaii async configuration will take care of routing the execution to the correct Executor.

4.4.4. Components

The following diagram shows the various components in the Hawaii async solution:

hawaii async task overview

In the diagram, MethodX is the call that must be executed asynchronously, for example service or repository method. The @Async annotation causes Spring to create a proxy around this method. The proxy locates the executor, which in the Hawaii case is a DelegatingExecutor which will delegate to the real executor specified for the task. The executor takes the MethodX Runnable and executes it on an available thread.

Additionally, a delayed (by the configured timeout) task, the MethodX Guard is created and passed to the Delayed Guard Executor.

Both tasks share the Shared Task Context which allows them to share logging context, and which also provides access for the guarded task to remove the guard task upon completion, and for the guard task to abort the guarded task upon activation.

4.4.5. Processing

The sequence below shows the components working together to execute a task.

hawaii async task overview normal

The sequence below shows the flow when a task times out.

hawaii async task overview timeout

5. Deployment



Appendix A: Hawaii application properties

Various properties can be specified inside your application.properties/application.yml file or as command line switches. This section provides a list of available Hawaii application properties.

# ===================================================================
# This sample file is provided as a guideline. Do NOT copy it in its
# entirety to your own application.               ^^^
# ===================================================================

	date-format: com.fasterxml.jackson.databind.util.ISO8601DateFormat
	  indent-output: false
	  write-dates-as-timestamps: false
	  write-date-timestamps-as-nanoseconds: false
  file: log/hawaii.log
	  org.hawaiiframework: INFO
	  org.springframework: INFO

    enabled: true # Enable creation of the `HawaiiTime` bean.
    timezone: UTC # The timezone to use like `UTC`, `Europe/Amsterdam` or `GMT+1`.
       configuration: ./config/async-config.yml # location of the Hawaii async configuration file


  profiles: dev
	serialization.indent-output: true
	org.hawaiiframework: DEBUG


  profiles: test


  profiles: prod