DSL.using(java)
   .toGoBeyond(BeanValidation)
   .at(JDK.IO);

Welcome to the Furets!

@dubreuia – Alexandre Dubreuil

  • French canadian working in Paris since 2009
  • Software Architect at LesFurets.com


@gdigugli – Gilles Di Guglielmo

  • Designer of sweet cooked software since 1999
  • Software Architect at LesFurets.com

  • 1 website, 5 Insurance Products : Car, Health, Home, Bike, Loan
  • 1 codebase, 450k lines of code, 60k unit tests, 150 selenium tests
  • 22 Developers, 2 DevOps, 4 Architects
  • 19 production servers including Load balancers, Frontend, Backend, Databases, BI
  • 1 release per day
  • 9 years of code history
  • 3M quotes/year, 40% of market share, 4M of customers

Introduction

LesFurets service orchestration

LesFurets service orchestration

Insurers partners

We have 71 live insurers, on 5 products, each with business validation rules,
that filter prospects based on their profile

Insurer exclusions

Hierarchy of 492 legacy classes, no governance or auditability

Use case: insurer exclusions

Insurer exclusions based on object model (legacy code)

                
public void check(FieldContext context, FormuleMoto formule, Conducteur conducteur,
                  Vehicule vehicule, Void unused, Besoins besoins,
                  Set<EAbTestingScenario> scenarios)
                  throws ExclusionException {
    if (besoins == null) {
        return;
    }
    if (besoins.getDateDebutContrat() == null) {
        return;
    }
    if (!DateHelper.isAfter(besoins.getDateDebutContrat(),
                    DateHelper.ajouteJoursADate(DateHelper.getToday(), NBR_JOURS),
                    DateHelper.EPrecision.jour)) {
        throw new ExclusionException(DATE_EFFET_PLUS_60_JOURS);
    }
}
                
              

Use case: goal

  • compliance: the rules correspond to the specification documents
  • auditability: understand a rule without looking at the code
  • governance: maintenance of the rules catalogue
  • clarity: productivity for developers

Same rule, more fluent:

                
public ExclusionRule exclusionRule() {
    return DOOV.when(dateContrat().after(todayPlusDays(60)))
               .exclusionRule();
}
                
              

Why a fluent API?

Java is verbose, but you can reduce the noise and write code like natural language with a fluent API

                
// JUnit API
assertEquals(9, fellowshipOfTheRing.size());
assertTrue(fellowshipOfTheRing.contains(frodo, sam));
assertFalse(fellowshipOfTheRing.contains(sauron));

// AssertJ API (fluent)
assertThat(fellowshipOfTheRing).hasSize(9)
                               .contains(frodo, sam)
                               .doesNotContain(sauron);
                
              

Fluent API

New elements in Java 8 makes it easier to write a fluent API

                
// java.util.function (io.doov.core.dsl.impl.LogicalBinaryCondition)
left.predicate().and(right.predicate()).test(model, context)

// java.util.stream (io.doov.core.dsl.impl.LogicalNaryCondition)
steps.stream().anyMatch(s -> s.predicate().test(model, context))

// lambda and method reference (io.doov.core.dsl.impl.NumericCondition)
predicate(greaterThanMetadata(field, value),
          (model, context) -> Optional.ofNullable(value),
          (l, r) -> greaterThanFunction().apply(l, r));
                
              

Fluent API

Many popular libraries propose fluent APIs like
jOOQ, AssertJ, Apache Spark, etc.

                
Dataset<Row> averagePrice = prices
        .filter(value.<String>getAs("insurer")
                     .equals("COOL insurer"))
        .groupBy("product")
        .agg(avg("price").as("average"))
        .orderBy(desc("average"));
                
              

DSL

"A domain-specific language (DSL) is a computer language specialized to a particular application domain. This is in contrast to a general-purpose language (GPL), which is broadly applicable across domains"

Meet dOOv!

Domain Object Oriented Validation

dOOv is a fluent API for typesafe domain model validation

dOOv ecosystem

How to write a validation rule?

key model

                    
// Root class of model
class Model {
  User user;
}

// Add key named EMAIL
enum ModelFieldId {
  EMAIL;
}

// Annotate email field
class User {
  @Path(field = EMAIL
        readable = ...)
  String email;
}
                    
                  

code generate

                    
// dOOv typed field class
class DslModel {
  StringFieldInfo userEmail;
}

// dOOv typed rule
class ModelRule {
  Result executeOn(Model m);
}
                    
                  

write rules

                    
// Create rules by using
// generated fields
// in DslModel
class Validations {
  ModelRule email = DslModel
    .when(userEmail.eq(...))
    .validate()

    // Optionaly add rules
    // to a registry
    .registerOn(DEFAULT);
}
                    
                  

How to validate a model

get model

                    
// Get model from somewhere
// or instanciate it
User user = new User();
user.setEmail("e@mail.com");

Model model = new Model();
model.setUser(user);
                    
                  

execute

                    
// Directly reference rule email
Validations.email.executeOn(model);

// Or use the registry
DEFAULT.stream()
  .map(rule -> rule.executeOn(model));
                    
                  

Keying a model

Keying a model

Live code

                
public class Account extends Identity {

    @SamplePath(field = SampleFieldId.TIMEZONE,
                readable = "account timezone")
    private Timezone timezone;

    @SamplePath(field = SampleFieldId.PHONE_NUMBER,
                readable = "account phone number")
    private String phoneNumber;

    @SamplePath(field = SampleFieldId.EMAIL,
                readable = "account email")
    private String email;

    @SamplePath(field = SampleFieldId.EMAIL_ACCEPTED,
                readable = "account email accepted")
    private boolean acceptEmail;

    @SamplePath(field = SampleFieldId.EMAILS_PREFERENCES,
                readable = "account préférences mail")
    private Collection<EmailType> emailTypes = new HashSet<>();

}
                
              

Live code: rewrite with dOOv

                
public static boolean validateAccount(User user, Account account, Configuration config) {
    if (config == null) {
        return false;
    }
    if (user == null || user.getBirthDate() == null) {
        return false;
    }
    if (account == null || account.getCountry() == null || account.getPhoneNumber() == null) {
        return false;
    }
    if (YEARS.between(user.getBirthDate(), LocalDate.now()) >= 18
                    && account.getEmail().length() <= config.getMaxEmailSize()
                    && account.getCountry().equals(Country.FR) 
                    && account.getPhoneNumber().startsWith("+33")) {
        return true;
    }
    return false;
}
                
              

Live code: result

                
public interface RulesConference {

  SampleModelRule userAccount = DslSampleModel
    // Entry point is when
    .when(userBirthdate.ageAt(today()).greaterOrEquals(18)
     .and(accountEmail.length().lesserOrEquals(configurationMaxEmailSize))
     .and(accountCountry.eq(Country.FR))
     .and(accountPhoneNumber.startsWith("+33")))
    // Terminal operation is validate
    .validate()
    // Optional: add to registry
    .registerOn(REGISTRY_DEFAULT);

}
                
              

Live code: test

                
public class RulesConferenceTest {

  private SampleModel model;

  @BeforeEach
  public void before() {
    model = SampleModels.sample();
  }

  @Test
  public void should_default_user_account_validates() {
    Result result = userAccount.executeOn(model);
    assertThat(result).isTrue().hasNoFailureCause();
  }

  @Test
  public void should_user_account_too_young_fail() {
    model.getAccount().setPhoneNumber(null);
    Result result = userAccount.executeOn(model);
    assertThat(result).isFalse()
                      .hasFailureCause("account phone number starts with '+33'");
  }

}
                
              

Live code: entry point

The entry point is DOOV#when(StepCondition) and the operation StepWhen#validate returns the validation rule

                
DOOV.when(accountEmail().matches("\\w+[@]\\w+\\.com")
      .or(accountEmail().matches("\\w+[@]\\w+\\.fr")))
    .validate();
                
              

This is lazy

Live code: entry point

We've used entry point DslSampleModel#when in the example: it makes typing simpler and more domain specific, but doesn't change execution.

Live code: natural language

A natural language version of the rule is available with ValidationRule#readable.

This makes auditability and compliance possible.

                
System.out.println("> " + EMAIL_VALID.readable());
                
              
                
> When (email matches '\w+[@]\w+\.com' or
email matches '\w+[@]\w+\.fr') validate
                
              

Live code: validation rule registry

You can add the rule in one or many registry with ValidationRule#registerOn(Registry)

This makes governance possible.

                
DOOV.when(accountEmail().matches("\\w+[@]\\w+\\.com")
      .or(accountEmail().matches("\\w+[@]\\w+\\.fr")))
   .validate()
   .registerOn(REGISTRY_ACCOUNT);
                
              

Live code: execution

The terminal operation ValidationRule#executeOn(FieldModel)
executes the rule

                
REGISTRY_ACCOUNT.stream()
    .map(rule -> rule.executeOn(model))
    .filter(Result::isInvalid)
    .map(Result::message)
    .collect(toList());
                
              

Live code: type safety

The available operations depend on the field type, and the arguments are type safe and validated by the compiler

                
DOOV.when(userAccountCreation().after(LocalDate.of(2000, 01, 01))).validate();
//                              ^^^^^
//                        only for date field
                
              
                
DOOV.when(userAccountCreation().after(LocalDate.of(2000, 01, 01))).validate();
//        ^^^^^^^^^^^^^^^^^^^         ^^^^^^^^^^^^^^^^^^^^^^^^^^^
//             date field                  is type safe here
                
              

Syntax tree

Why a syntax tree?

Makes readable text generation possible:
we can output a multi-language rules catalog
in multiple formats (text, markdown, HTML, etc.)

LesFurets rules catalog

We generate a HTML validation rules catalog,
grouped by insurers and by insurance product

Rules catalog

The syntax tree makes it possible to generate the rule as text. Notice how the elements from the tree are tokenized (operator, fields, etc.)

Rules catalog

Also, the syntax tree makes it possible to see all the rules that applies for a specific field, for example the driver's date of birth.

i18n of the syntax tree

The syntax tree is localized for left side elements (fields) and operators via MessageBundle.

                
// User.java
@SamplePath(field = SampleFieldId.FIRST_NAME, 
            readable = "user.first.name")
private String firstName;
                
              
                
// SampleResourceBundle_en_US.properties
user.first.name = user first name

// SampleResourceBundle_fr_FR.properties
user.first.name = prénom utilisateur
                
              

You can also specify the text directly in the readable field.

i18n of the syntax tree

You can use ValidationRule#readable(Locale) and Result#getFailureCause(Locale) to specify a locale

                
// Output in default Locale.getDefault()
String readable = DOOV.when(userFirstName.isNotNull())
                      .readable())
System.out.println("> " + readable);
                
              
                
> when first name exists
                
              
                
// Output in french
String readable = DOOV.when(userFirstName.isNotNull())
                      .readable(Locale.FRANCE))
System.out.println("> " + readable)
                
              
                
> lorsque prénom utilisateur existe
                
              

Execution statistics

During execution, each node of the AST captures context value and predicate result. We know at runtime which node failed, and why.

Execution statistics

We make daily statistics that helps us shape the business,
by removing or tweaking rules as needed

Execution statistics

We also rewrite the execution rules by simplifying the predicate tree, to show the minimal predicate that fails.

Failure cause - and / or

Validate that the profile has an email with less than 20 characters, is at least 18 years old when the country is France, and the country is France when the phone number starts with '+33'

                
DOOV.when(accountEmail.length().lesserThan(20)
      .and(userBirthdate.ageAt(today()).greaterThan(18)
        .and(accountCountry.eq(Country.FR)))
      .and(accountCountry.eq(Country.FR)
        .and(accountPhoneNumber.startsWith("+33"))))
    .validate();
                
              

Failure cause - and / or

                
model.getAccount().setEmail("test@test.org");
model.getAccount().setCountry(Country.FR);
model.getUser().setBirthDate(LocalDate.now().minusYears(19));

ValidationRule rule = DOOV
    .when(accountEmail.length().lesserThan(20)  
      .and(userBirthdate.ageAt(today()).greaterThan(18)
        .and(accountCountry.eq(Country.FR)))
      .and(accountCountry.eq(Country.FR)
        .and(accountPhoneNumber.startsWith("+33"))))
    .validate();

Result result = rule.withShortCircuit(false)
                    .executeOn(wrapper);
System.out.println("> " + result.getFailureCause());
                
              
                
> account phone number starts with '+33'
                
              

Failure cause - matchAny / matchAll

Validate that the profile is least 18 years old, the country is France, the phone number starts with '+33', is at least 21 years old when their country is Canada, and their phone number starts with '+1'

                
DOOV.when(matchAny(
      matchAll(userBirthdate.ageAt(today()).greaterThan(18),
               accountCountry.eq(Country.FR),
               accountPhoneNumber.startsWith("+33")),
      matchAll(userBirthdate.ageAt(today()).greaterThan(21),
               accountCountry.eq(Country.CAN),
               accountPhoneNumber.startsWith("+1"))))
    .validate();
                
              

Failure cause - matchAny / matchAll

                
model.getUser().setBirthDate(LocalDate.now().minusYears(22));
model.getAccount().setCountry(Country.FR);

ValidationRule rule = DOOV
    .when(matchAny(
        matchAll(userBirthdate.ageAt(today()).greaterThan(18),
                 accountCountry.eq(Country.FR),
                 accountPhoneNumber.startsWith("+33")),
        matchAll(userBirthdate.ageAt(today()).greaterThan(21),
                 accountCountry.eq(Country.CAN),
                 accountPhoneNumber.startsWith("+1"))))
    .validate();

Result result = rule.withShortCircuit(false)
                    .executeOn(wrapper);
System.out.println("> " + result.getFailureCause());
                
              
                
> match any [account phone number starts with '+33',
             match all [account country = CAN,
                        account phone number starts with '+1']]
                
              

Execution short-circuit

By default, predicate evaluation in dOOv behaves like Java: it short-circuits. This can be disabled to execute all nodes, even if they don't impact the end result.

Beyond bean validation

Performance - Java Microbenchmark Harness

We use JMH to check the performance of the DSL

                
Benchmark                          Mode  Samples      Mean  Mean error   Units
o.m.BenchmarkOldRule.valid_email  thrpt       25  1860.553      42.269  ops/ms
o.m.BenchmarkRule.valid_email     thrpt       25  1733.465      18.461  ops/ms
                
              

Performance of the DSL and POJO code are very close

Performance - comparing with Hibernate Validator

Running the Bean Validation benchmark:
dOOv is faster in every category (hint: reflection API)

Visit our blog for details: https://beastie.lesfurets.com

Beyond Bean Validation: types

Bean Validation rules are not strongly typed since it's annotation based. This code will fail at compile time, but your IDE won't be able to tell you why.

                
public class Account {

    @NotNull @Email
    private Email email;

}
                
              

Beyond Bean Validation: complex validation

Because Bean Validation constraints are based on field annotation, cross validation between fields are only available through the extension mechanism.

                
public class Account {

    @Pattern(regexp = "(FR)|(UK)")
    private String country;

    @Pattern(regexp = "???")
    private String phoneNumber;

}
                
              

Beyond Bean Validation: natural language

Bean Validation rules are not written with a natural language syntax and does not provide a syntax tree

                
@Size(min = 10, max = 200,
      message = "About Me must be between 10 and 200 characters")
private String aboutMe;
                
              

DSL

                
userAboutMe().length().between(10, 200).validate().readable()
> When user about me length is between 10 and 200, validate
                
              

Beyond Bean Validation: syntax versus consistency

 

Bean Validation allows syntax validation
 
 
Bean Validation rules are written on the model
 
 
Bean Validation uses reflection
dOOv allows consistency checks
 
 
dOOv rules are writtent outside of the model, allowing complex checks
 
 
dOOv uses code generation

Conclusion

Goal

We migrated our 492 business rules to dOOv,
we now have compliance, auditability, governance, clarity
(and more!)

Roadmap

Next step is extending the DSL to create an object to object mapping framework, Domain Object Oriented Mapping (dOOm). It will feature the same AST to text and statistics functionnalities.

                
DOOV.map(userEmail().to(insurerEmail())
    .map(userFirstName(), userLastName())
      .using(StringJoiner)
      .to(insurerFullName())
    .when(userCountry().eq(FR))
      .map(userPhone().to(insurerPhone()))
                
              

Stay tuned for the next versions!

Enjoy dOOv.io

http://www.dOOv.io

Appendices

Failure cause - sample 1

Validate that a profile
has an email with less than 20 characters
has at least 18 years when their country is France
their country is France when their phone number starts with '+33'

                
DOOV.when(accountEmail.length().lesserThan(20)
      .and(userBirthdate.ageAt(today()).greaterThan(18)
        .and(accountCountry.eq(Country.FR)))
      .and(accountCountry.eq(Country.FR)
        .and(accountPhoneNumber.startsWith("+33"))))
    .validate();
                
              

Failure cause - sample 1

                
model.getAccount().setEmail("test@test.org");
model.getAccount().setCountry(Country.FR);
model.getUser().setBirthDate(LocalDate.now().minusYears(19));

ValidationRule rule = DOOV
    .when(accountEmail.length().lesserThan(20)  
      .and(userBirthdate.ageAt(today()).greaterThan(18)
          .and(accountCountry.eq(Country.FR)))
      .and(accountCountry.eq(Country.FR)
          .and(accountPhoneNumber.startsWith("+33"))))
    .validate();

Result result = rule.withShortCircuit(false)
                    .executeOn(wrapper);
System.out.println("> " + result.getFailureCause());
                
              
                
> account phone number starts with '+33'
                
              

Failure cause - sample 2

Validate that a profile
has at least 18 years when their country is France
and their phone number starts with '+33'
has at least 21 years when their country is Canadian
and their phone number starts with '+1'

                  
DOOV.when(userBirthdate.ageAt(today()).greaterThan(18)
        .and(accountCountry.eq(Country.FR)
        .and(accountPhoneNumber.startsWith("+33")))
        .or(userBirthdate.ageAt(today()).greaterThan(21)
              .and(accountCountry.eq(Country.CAN)
              .and(accountPhoneNumber.startsWith("+1")))))
    .validate();
                  
                

Failure cause - sample 2

                
model.getUser().setBirthDate(LocalDate.now().minusYears(22));
model.getAccount().setCountry(Country.FR);

ValidationRule rule = DOOV
    .when(userBirthdate.ageAt(today()).greaterThan(18)
        .and(accountCountry.eq(Country.FR)
        .and(accountPhoneNumber.startsWith("+33")))
        .or(userBirthdate.ageAt(today()).greaterThan(21)
              .and(accountCountry.eq(Country.CAN)
              .and(accountPhoneNumber.startsWith("+1")))))
    .validate();

Result result = rule.withShortCircuit(false)
                    .executeOn(wrapper);
System.out.println("> " + result.getFailureCause());
                
              
                
> account phone number starts with '+33'
    or (account country = CAN and
        account phone number starts with '+1')
                
              

Failure cause - sample 3

Validate that a profile
has at least 18 years when their country is France
and their phone number starts with '+33'
has at least 21 years when their country is Canadian
and their phone number starts with '+1'

                  
DOOV.when(matchAny(
        matchAll(userBirthdate.ageAt(today()).greaterThan(18),
                 accountCountry.eq(Country.FR),
                 accountPhoneNumber.startsWith("+33")),
        matchAll(userBirthdate.ageAt(today()).greaterThan(21),
                 accountCountry.eq(Country.CAN),
                 accountPhoneNumber.startsWith("+1"))))
     .validate();
                 
                

Failure cause - sample 3

                
model.getUser().setBirthDate(LocalDate.now().minusYears(22));
model.getAccount().setCountry(Country.FR);

ValidationRule rule = DOOV
    .when(matchAny(
        matchAll(userBirthdate.ageAt(today()).greaterThan(18),
                 accountCountry.eq(Country.FR),
                 accountPhoneNumber.startsWith("+33")),
        matchAll(userBirthdate.ageAt(today()).greaterThan(21),
                 accountCountry.eq(Country.CAN),
                 accountPhoneNumber.startsWith("+1"))))
    .validate();

Result result = rule.withShortCircuit(false)
                    .executeOn(wrapper);
System.out.println("> " + result.getFailureCause());
                
              
                
> match any [account phone number starts with '+33',
             match all [account country = CAN,
                        account phone number starts with '+1']]
                
              

Failure cause - sample 4

Validate that a profile country is Canadian or French

                
DOOV.when(accountCountry.anyMatch(Country.CAN, Country.FR))
    .validate();
                
              

Failure cause - sample 4

                
model.getAccount().setCountry(Country.UK);

ValidationRule rule = DOOV
    .when(accountCountry.anyMatch(Country.CAN, Country.FR))
    .validate();

Result result = rule.withShortCircuit(false)
                    .executeOn(wrapper);
System.out.println("> " + result.getFailureCause());
                
              
                
> account country != UK
                
              

Failure cause - sample 5

Validate that a profile match at least two conditions :

  • profile has at least 18 years
  • country is France
  • phone number starts with '+33'

                
DOOV.when(count(
      userBirthdate.ageAt(today()).greaterThan(18),
      accountCountry.eq(Country.FR),
      accountPhoneNumber.startsWith("+33")).greaterThan(1))
    .validate();
                
              

Failure cause - sample 5

                
model.getUser().setBirthDate(LocalDate.now().minusYears(19));
model.getAccount().setCountry(Country.CAN);
model.getAccount().setPhoneNumber("1 23 45 67 89");

ValidationRule rule = DOOV
    .when(count(
            userBirthdate.ageAt(today()).greaterThan(18),
            accountCountry.eq(Country.FR),
            accountPhoneNumber.startsWith("+33"))
        .greaterThan(1))
    .validate();

Result result = rule.withShortCircuit(false)
                    .executeOn(wrapper);
System.out.println("> " + result.getFailureCause());
                
              
                
> account country = FR and account phone number starts with '+33'