Implement validator using Visitor pattern and move Customer to a dedicated package (#71)

Author: mperor

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/CorporateCustomer.java

@@ -0,0 +1,4 @@
+package pl.mperor.lab.java.design.pattern.behavioral.visitor.customer;
+
+record CorporateCustomer() implements Customer {
+}

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/Letter.java

@@ -1,4 +1,4 @@
-package pl.mperor.lab.java.design.pattern.behavioral.visitor;
+package pl.mperor.lab.java.design.pattern.behavioral.visitor.customer;
 
 public sealed interface Customer permits CorporateCustomer, RegularCustomer, PremiumCustomer {
 

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/PremiumCustomer.java

@@ -1,4 +1,4 @@
-package pl.mperor.lab.java.design.pattern.behavioral.visitor;
+package pl.mperor.lab.java.design.pattern.behavioral.visitor.customer;
 
 public interface CustomerVisitor<T> {
 

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/RegularCustomer.java

@@ -1,4 +1,4 @@
-package pl.mperor.lab.java.design.pattern.behavioral.visitor;
+package pl.mperor.lab.java.design.pattern.behavioral.visitor.customer;
 
 enum DiscountLevel {
     BRONZE(10),

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/customer/CorporateCustomer.java

@@ -1,4 +1,4 @@
-package pl.mperor.lab.java.design.pattern.behavioral.visitor;
+package pl.mperor.lab.java.design.pattern.behavioral.visitor.customer;
 
 public class DiscountProvider implements CustomerVisitor<DiscountLevel> {
 

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/Customer.java renamed to DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/customer/Customer.java

@@ -1,4 +1,4 @@
-package pl.mperor.lab.java.design.pattern.behavioral.visitor;
+package pl.mperor.lab.java.design.pattern.behavioral.visitor.customer;
 
 public class InvitationLetterGenerator implements CustomerVisitor<Letter> {
 

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/CustomerVisitor.java renamed to DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/customer/CustomerVisitor.java

@@ -0,0 +1,4 @@
+package pl.mperor.lab.java.design.pattern.behavioral.visitor.customer;
+
+record Letter(String content) {
+}

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/DiscountLevel.java renamed to DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/customer/DiscountLevel.java

@@ -0,0 +1,4 @@
+package pl.mperor.lab.java.design.pattern.behavioral.visitor.customer;
+
+record PremiumCustomer() implements Customer {
+}

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/DiscountProvider.java renamed to DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/customer/DiscountProvider.java

@@ -0,0 +1,4 @@
+package pl.mperor.lab.java.design.pattern.behavioral.visitor.customer;
+
+record RegularCustomer() implements Customer {
+}

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/InvitationLetterGenerator.java renamed to DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/customer/InvitationLetterGenerator.java

@@ -0,0 +1,22 @@
+package pl.mperor.lab.java.design.pattern.behavioral.visitor.validator;
+
+import java.util.ArrayList;
+import java.util.List;
+
+class AggregatingValidationExceptionHandler implements ValidationExceptionHandler {
+
+    private List<ValidationException> errors = new ArrayList<>();
+
+    @Override
+    public void handle(ValidationException exception) {
+        errors.add(exception);
+    }
+
+    boolean hasErrors() {
+        return !errors.isEmpty();
+    }
+
+    public List<ValidationException> getErrors() {
+        return List.copyOf(errors);
+    }
+}

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/customer/Letter.java

@@ -0,0 +1,29 @@
+package pl.mperor.lab.java.design.pattern.behavioral.visitor.validator;
+
+import java.util.regex.Pattern;
+
+record Email(String address) {
+
+    public Email {
+        test(address, new ThrowingValidationExceptionHandler());
+    }
+
+    public static void test(String address, ValidationExceptionHandler handler) {
+        new EmailValidator().validate(address, handler);
+    }
+
+    static class EmailValidator implements Validator<String> {
+
+        public static final Pattern FORMAT_PATTERN = Pattern.compile("^[a-zA-Z0-9+_.-]+@[a-zA-Z0-9.-]+$");
+
+        @Override
+        public void validate(String address, ValidationExceptionHandler validationExceptionHandler) {
+            if (FORMAT_PATTERN.asMatchPredicate().negate().test(address)) {
+                validationExceptionHandler.handle(new InvalidFormatException());
+            }
+        }
+    }
+
+    static class InvalidFormatException extends ValidationException {
+    }
+}

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/customer/PremiumCustomer.java

@@ -0,0 +1,25 @@
+package pl.mperor.lab.java.design.pattern.behavioral.visitor.validator;
+
+record Password(String value) {
+
+    public Password {
+        Password.test(value, new ThrowingValidationExceptionHandler());
+    }
+
+    public static void test(String password, ValidationExceptionHandler validationExceptionHandler) {
+        new PasswordValidator().validate(password, validationExceptionHandler);
+    }
+
+    static class PasswordValidator implements Validator<String> {
+
+        @Override
+        public void validate(String password, ValidationExceptionHandler validationExceptionHandler) {
+            if (password.length() < 8 || password.length() > 16) {
+                validationExceptionHandler.handle(new InvalidLengthException());
+            }
+        }
+    }
+
+    static class InvalidLengthException extends ValidationException {
+    }
+}

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/customer/RegularCustomer.java

@@ -0,0 +1,9 @@
+package pl.mperor.lab.java.design.pattern.behavioral.visitor.validator;
+
+class ThrowingValidationExceptionHandler implements ValidationExceptionHandler{
+
+    @Override
+    public void handle(ValidationException exception) {
+        throw exception;
+    }
+}

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/validator/AggregatingValidationExceptionHandler.java

@@ -0,0 +1,4 @@
+package pl.mperor.lab.java.design.pattern.behavioral.visitor.validator;
+
+abstract class ValidationException extends RuntimeException {
+}

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/validator/Email.java

@@ -0,0 +1,6 @@
+package pl.mperor.lab.java.design.pattern.behavioral.visitor.validator;
+
+interface ValidationExceptionHandler {
+
+    void handle(ValidationException exception);
+}

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/validator/Password.java

@@ -0,0 +1,6 @@
+package pl.mperor.lab.java.design.pattern.behavioral.visitor.validator;
+
+interface Validator<T> {
+
+    void validate(T toValid, ValidationExceptionHandler validationExceptionHandler);
+}

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/validator/ThrowingValidationExceptionHandler.java

@@ -1,4 +1,4 @@
-package pl.mperor.lab.java.design.pattern.behavioral.visitor;
+package pl.mperor.lab.java.design.pattern.behavioral.visitor.customer;
 
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/visitor/validator/ValidationException.java

@@ -0,0 +1,26 @@
+package pl.mperor.lab.java.design.pattern.behavioral.visitor.validator;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+class ValidatorVisitorTest {
+
+    @Test
+    public void testValidatePasswordAndEmailWithExceptionAggregation() {
+        var aggregationHandler = new AggregatingValidationExceptionHandler();
+        Password.test("xyz", aggregationHandler);
+        Email.test("user1$gmail.com", aggregationHandler);
+        Assertions.assertTrue(aggregationHandler.hasErrors());
+        Assertions.assertEquals(aggregationHandler.getErrors().size(), 2);
+    }
+
+    @Test
+    public void testValidatePasswordAndEmailWithExceptionThrowing() {
+        Assertions.assertThrows(Password.InvalidLengthException.class, () -> new Password("xyz"));
+        Assertions.assertThrows(Email.InvalidFormatException.class, () -> new Email("user1$gmail.com"));
+
+        var throwingHandler = new ThrowingValidationExceptionHandler();
+        Assertions.assertThrows(Password.InvalidLengthException.class, () -> Password.test("xyz", throwingHandler));
+        Assertions.assertThrows(Email.InvalidFormatException.class, () -> Email.test("user1$gmail.com", throwingHandler));
+    }
+}