Bael 7436 (#15550)

* BAEL-7436: Initial Unit Tests

* BAEL-7436: Added an Example with Service

* BAEL-7436: Cleanup and test fixes

* BAEL-7436: Test rename

* BAEL-7436: Cleanup

* BAEL-7436: Fix pom

* BAEL-7436: Test rename

patterns-modules/design-patterns-behavioral-2/pom.xml

@@ -14,4 +14,20 @@
         <version>1.0.0-SNAPSHOT</version>
     </parent>
 
+    <dependencies>
+      <dependency>
+          <groupId>org.apache.commons</groupId>
+          <artifactId>commons-lang3</artifactId>
+          <version>${apache.commons.version}</version>
+      </dependency>
+      <dependency>
+          <groupId>com.google.guava</groupId>
+          <artifactId>guava</artifactId>
+          <version>${guava.version}</version>
+      </dependency>
+    </dependencies>
+
+    <properties>
+      <apache.commons.version>3.14.0</apache.commons.version>
+    </properties>
 </project>

patterns-modules/design-patterns-behavioral-2/src/main/java/com/baeldung/nullconversion/Address.java

@@ -0,0 +1,26 @@
+package com.baeldung.nullconversion;
+
+public class Address implements Cloneable {
+
+    private ZipCode zipCode;
+
+    public ZipCode getZipCode() {
+        return zipCode;
+    }
+
+    public void setZipCode(ZipCode zipCode) {
+        this.zipCode = zipCode;
+    }
+
+    @Override
+    protected Address clone()  {
+        Address address;
+        try {
+            address = ((Address) super.clone());
+        } catch (CloneNotSupportedException e) {
+            throw new RuntimeException(e);
+        }
+        zipCode = zipCode.clone();
+        return address;
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/main/java/com/baeldung/nullconversion/Delivery.java

@@ -0,0 +1,35 @@
+package com.baeldung.nullconversion;
+
+import java.util.Objects;
+
+public class Delivery {
+
+    private String message;
+
+    public Delivery(String message) {
+        this.message = message;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+
+        Delivery delivery = (Delivery) o;
+
+        return Objects.equals(message, delivery.message);
+    }
+
+    @Override
+    public int hashCode() {
+        return message != null ? message.hashCode() : 0;
+    }
+
+    public static Delivery freeDelivery() {
+        return new Delivery("Free delivery");
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/main/java/com/baeldung/nullconversion/DeliveryService.java

@@ -0,0 +1,6 @@
+package com.baeldung.nullconversion;
+
+public interface DeliveryService {
+
+    Delivery calculateDeliveryForPerson(Long id);
+}

patterns-modules/design-patterns-behavioral-2/src/main/java/com/baeldung/nullconversion/Person.java

@@ -0,0 +1,26 @@
+package com.baeldung.nullconversion;
+
+public class Person implements Cloneable {
+
+    private Address address;
+
+    public Address getAddress() {
+        return address;
+    }
+
+    public void setAddress(Address address) {
+        this.address = address;
+    }
+
+    @Override
+    protected Person clone() {
+        Person person;
+        try {
+            person = (Person) super.clone();
+        } catch (CloneNotSupportedException e) {
+            throw new RuntimeException(e);
+        }
+        address = address.clone();
+        return person;
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/main/java/com/baeldung/nullconversion/ZipCode.java

@@ -0,0 +1,27 @@
+package com.baeldung.nullconversion;
+
+public class ZipCode implements Cloneable {
+
+    private String code;
+
+    public ZipCode(String code) {
+        this.code = code;
+    }
+
+    public String getCode() {
+        return code;
+    }
+
+    @Override
+    protected ZipCode clone() {
+        try {
+            return (ZipCode) super.clone();
+        } catch (CloneNotSupportedException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public void setCode(String code) {
+        this.code = code;
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/NullConversionUnitTest.java

@@ -0,0 +1,130 @@
+package com.baeldung.nullconversion;
+
+import static java.util.Objects.requireNonNullElse;
+import static java.util.Objects.requireNonNullElseGet;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+
+import com.google.common.base.MoreObjects;
+import java.util.Optional;
+import java.util.function.Supplier;
+import org.apache.commons.lang3.ObjectUtils;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ArgumentsSource;
+
+class NullConversionUnitTest {
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsProvider.class)
+    void givenIfWhenNotNullThenReturnsDefault(String givenValue, String defaultValue) {
+        String actual = defaultValue;
+        if (givenValue != null) {
+            actual = givenValue;
+        }
+        assertDefaultConversion(givenValue, defaultValue, actual);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsSupplierProvider.class)
+    void givenIfWhenNotNullThenReturnsDefault(String givenValue, String expected,
+      Supplier<String> expensiveSupplier) {
+        String actual;
+        if (givenValue != null) {
+            actual = givenValue;
+        } else {
+            actual = expensiveSupplier.get();
+        }
+        assertDefaultConversion(givenValue, expected, actual);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsProvider.class)
+    void givenTernaryWhenNotNullThenReturnsDefault(String givenValue, String defaultValue) {
+        String actual = givenValue != null ? givenValue : defaultValue;
+        assertDefaultConversion(givenValue, defaultValue, actual);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsSupplierProvider.class)
+    void givenLazyTernaryWhenNotNullThenReturnsDefault(String givenValue, String expected,
+      Supplier<String> expensiveSupplier) {
+        String actual = givenValue != null ? givenValue : expensiveSupplier.get();
+        assertDefaultConversion(givenValue, expected, actual);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsProvider.class)
+    void givenObjectsWhenNotNullThenReturnsDefault(String givenValue, String defaultValue) {
+        String actual = requireNonNullElse(givenValue, defaultValue);
+        assertDefaultConversion(givenValue, defaultValue, actual);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsSupplierProvider.class)
+    void givenLazyObjectsWhenNotNullThenReturnsDefault(String givenValue, String expected,
+      Supplier<String> expensiveSupplier) {
+        String actual = requireNonNullElseGet(givenValue, expensiveSupplier);
+        assertDefaultConversion(givenValue, expected, actual);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsProvider.class)
+    void givenOptionalWhenNotNullThenReturnsDefault(String givenValue, String defaultValue) {
+        String actual = Optional.ofNullable(givenValue).orElse(defaultValue);
+        assertDefaultConversion(givenValue, defaultValue, actual);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsSupplierProvider.class)
+    void givenLazyOptionalWhenNotNullThenReturnsDefault(String givenValue, String expected,
+      Supplier<String> expensiveSupplier) {
+        String actual = Optional.ofNullable(givenValue).orElseGet(expensiveSupplier);
+        assertDefaultConversion(givenValue, expected, actual);
+    }
+
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsProvider.class)
+    void givenGuavaWhenNotNullThenReturnsDefault(String givenValue, String defaultValue) {
+        String actual = MoreObjects.firstNonNull(givenValue, defaultValue);
+        assertDefaultConversion(givenValue, defaultValue, actual);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsProvider.class)
+    void givenGuavaOptionalWhenNotNullThenReturnsDefault(String givenValue, String defaultValue) {
+        String actual = com.google.common.base.Optional.fromNullable(givenValue).or(defaultValue);
+        assertDefaultConversion(givenValue, defaultValue, actual);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsProvider.class)
+    void givenApacheWhenNotNullThenReturnsDefault(String givenValue, String defaultValue) {
+        String actual = ObjectUtils.firstNonNull(givenValue, defaultValue);
+        assertDefaultConversion(givenValue, defaultValue, actual);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsSupplierProvider.class)
+    void givenLazyApacheWhenNotNullThenReturnsDefault(String givenValue, String expected,
+      Supplier<String> expensiveSupplier) {
+        String actual = ObjectUtils.getFirstNonNull(() -> givenValue, expensiveSupplier);
+        assertDefaultConversion(givenValue, expected, actual);
+    }
+
+    @Test
+    void givenAllNullsWithObjectsWhenNotNullThenThrowException() {
+        assertThatExceptionOfType(NullPointerException.class)
+          .isThrownBy(() -> requireNonNullElse(null, null));
+    }
+
+    private static void assertDefaultConversion(String given, String expected, String actual) {
+        if (given == null) {
+            assertThat(actual).isEqualTo(expected);
+        } else {
+            assertThat(actual).isEqualTo(given);
+        }
+    }
+
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/NullReturningPersonChainProvider.java

@@ -0,0 +1,26 @@
+package com.baeldung.nullconversion;
+
+import java.util.stream.Stream;
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.ArgumentsProvider;
+
+public class NullReturningPersonChainProvider implements ArgumentsProvider {
+
+    @Override
+    public Stream<? extends Arguments> provideArguments(ExtensionContext context) {
+        Person person = new Person();
+        Address address = new Address();
+        ZipCode zipCode = new ZipCode("98-323");
+        address.setZipCode(zipCode);
+        person.setAddress(address);
+
+        return Stream.of(
+          Arguments.of(PersonMutatorUtil.cloneAndMutate(person, p -> p.getAddress().getZipCode().setCode(""))),
+          Arguments.of(PersonMutatorUtil.cloneAndMutate(person, p -> p.getAddress().setZipCode(null))),
+          Arguments.of(PersonMutatorUtil.cloneAndMutate(person, p -> p.setAddress(null)))
+        );
+
+    }
+
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/ObjectsProvider.java

@@ -0,0 +1,18 @@
+package com.baeldung.nullconversion;
+
+import java.util.stream.Stream;
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.ArgumentsProvider;
+
+public class ObjectsProvider implements ArgumentsProvider {
+
+    @Override
+    public Stream<? extends Arguments> provideArguments(ExtensionContext context) {
+        return Stream.of(
+          Arguments.of(null, "default"),
+          Arguments.of("not null", "default")
+        );
+
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/ObjectsSupplierProvider.java

@@ -0,0 +1,20 @@
+package com.baeldung.nullconversion;
+
+import java.util.function.Supplier;
+import java.util.stream.Stream;
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.ArgumentsProvider;
+
+public class ObjectsSupplierProvider implements ArgumentsProvider {
+
+    @Override
+    public Stream<? extends Arguments> provideArguments(ExtensionContext context) {
+        Supplier<String> supplier = () -> "default";
+        return Stream.of(
+          Arguments.of(null, "default", supplier),
+          Arguments.of("not null", "default", supplier)
+        );
+
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/OnePersonDeliveryServiceUnitTest.java

@@ -0,0 +1,39 @@
+package com.baeldung.nullconversion;
+
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+
+import com.baeldung.nullconversion.service.OnePersonExplicitDeliveryService;
+import com.baeldung.nullconversion.service.OnePersonGuavaOptionalDeliveryService;
+import com.baeldung.nullconversion.service.OnePersonOptionalDeliveryService;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ArgumentsSource;
+
+class OnePersonDeliveryServiceUnitTest {
+
+    @ParameterizedTest
+    @ArgumentsSource(PersonProvider.class)
+    void givenMockDeliverServiceWhenNullValuesThenExplicitServiceHandleThem(Person person, Delivery expected) {
+        DeliveryService deliveryService = new OnePersonExplicitDeliveryService(person);
+        Delivery actual = deliveryService.calculateDeliveryForPerson(1L);
+        assertThat(actual).isEqualTo(expected);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(PersonProvider.class)
+    void givenMockDeliverServiceWhenNullValuesThenOptionalServiceHandleThem(Person person, Delivery expected) {
+        DeliveryService deliveryService = new OnePersonOptionalDeliveryService(person);
+        Delivery actual = deliveryService.calculateDeliveryForPerson(1L);
+        assertThat(actual).isEqualTo(expected);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(NullReturningPersonChainProvider.class)
+    void givenMockDeliverServiceWhenNullValuesThenGuavaOptionalServiceThrowsException(Person person) {
+        DeliveryService deliveryService = new OnePersonGuavaOptionalDeliveryService(person);
+        assertThatExceptionOfType(NullPointerException.class)
+          .isThrownBy(() -> deliveryService.calculateDeliveryForPerson(1L));
+
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/PersonMutatorUtil.java

@@ -0,0 +1,12 @@
+package com.baeldung.nullconversion;
+
+import java.util.function.Consumer;
+
+public class PersonMutatorUtil {
+
+    public static Person cloneAndMutate(Person person, Consumer<Person> mutator) {
+        Person clone = person.clone();
+        mutator.accept(clone);
+        return clone;
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/PersonProvider.java

@@ -0,0 +1,34 @@
+package com.baeldung.nullconversion;
+
+import java.util.function.Consumer;
+import java.util.stream.Stream;
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.ArgumentsProvider;
+
+public class PersonProvider implements ArgumentsProvider {
+
+    @Override
+    public Stream<? extends Arguments> provideArguments(ExtensionContext context) {
+        Person person = new Person();
+        Address address = new Address();
+        ZipCode zipCode = new ZipCode("98-323");
+        address.setZipCode(zipCode);
+        person.setAddress(address);
+
+        return Stream.of(
+          Arguments.of(person, Delivery.freeDelivery()),
+          Arguments.of(cloneAndMutate(person, p -> p.getAddress().getZipCode().setCode("")), null),
+          Arguments.of(cloneAndMutate(person, p -> p.getAddress().setZipCode(null)), null),
+          Arguments.of(cloneAndMutate(person, p -> p.setAddress(null)), null),
+          Arguments.of(null, null)
+        );
+
+    }
+
+    private static Person cloneAndMutate(Person person, Consumer<Person> mutator) {
+        Person clone = person.clone();
+        mutator.accept(clone);
+        return clone;
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/service/MockOnePersonDeliveryServiceBase.java

@@ -0,0 +1,50 @@
+package com.baeldung.nullconversion.service;
+
+import com.baeldung.nullconversion.Address;
+import com.baeldung.nullconversion.Delivery;
+import com.baeldung.nullconversion.DeliveryService;
+import com.baeldung.nullconversion.Person;
+import com.baeldung.nullconversion.ZipCode;
+import java.util.Optional;
+
+public abstract class MockOnePersonDeliveryServiceBase implements DeliveryService {
+
+    private final Person person;
+
+    public MockOnePersonDeliveryServiceBase(Person person) {
+        this.person = person;
+    }
+
+    @Override
+    public Delivery calculateDeliveryForPerson(Long id) {
+        Person person = getPersonById(id);
+        if (person != null && person.getAddress() != null && person.getAddress().getZipCode() != null) {
+            ZipCode zipCode = person.getAddress().getZipCode();
+            String code = zipCode.getCode();
+            return calculateDeliveryForZipCode(code);
+        }
+        return null;
+    }
+
+    public Delivery calculateDeliveryForPersonWithOptional(Long id) {
+        return Optional.ofNullable(getPersonById(id))
+          .map(Person::getAddress)
+          .map(Address::getZipCode)
+          .map(ZipCode::getCode)
+          .map(this::calculateDeliveryForZipCode)
+          .orElse(null);
+    }
+
+    protected Person getPersonById(Long id) {
+        return person;
+    }
+
+    protected Delivery calculateDeliveryForZipCode(String zipCode) {
+        if (zipCode == null || zipCode.isEmpty()) {
+            return null;
+        } else {
+            return Delivery.freeDelivery();
+        }
+    }
+
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/service/OnePersonExplicitDeliveryService.java

@@ -0,0 +1,24 @@
+package com.baeldung.nullconversion.service;
+
+import com.baeldung.nullconversion.Delivery;
+import com.baeldung.nullconversion.Person;
+import com.baeldung.nullconversion.ZipCode;
+
+public class OnePersonExplicitDeliveryService extends MockOnePersonDeliveryServiceBase {
+
+
+    public OnePersonExplicitDeliveryService(Person person) {
+        super(person);
+    }
+
+    @Override
+    public Delivery calculateDeliveryForPerson(Long id) {
+        Person person = getPersonById(id);
+        if (person != null && person.getAddress() != null && person.getAddress().getZipCode() != null) {
+            ZipCode zipCode = person.getAddress().getZipCode();
+            String code = zipCode.getCode();
+            return calculateDeliveryForZipCode(code);
+        }
+        return null;
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/service/OnePersonGuavaOptionalDeliveryService.java

@@ -0,0 +1,26 @@
+package com.baeldung.nullconversion.service;
+
+import com.baeldung.nullconversion.Address;
+import com.baeldung.nullconversion.Delivery;
+import com.baeldung.nullconversion.Person;
+import com.baeldung.nullconversion.ZipCode;
+import com.google.common.base.Optional;
+
+public class OnePersonGuavaOptionalDeliveryService extends MockOnePersonDeliveryServiceBase {
+
+
+    public OnePersonGuavaOptionalDeliveryService(Person person) {
+        super(person);
+    }
+
+    @Override
+    public Delivery calculateDeliveryForPerson(Long id) {
+        return Optional.fromNullable(getPersonById(id))
+          .transform(Person::getAddress)
+          .transform(Address::getZipCode)
+          .transform(ZipCode::getCode)
+          .transform(this::calculateDeliveryForZipCode)
+          .orNull();
+    }
+
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/service/OnePersonOptionalDeliveryService.java

@@ -0,0 +1,26 @@
+package com.baeldung.nullconversion.service;
+
+import com.baeldung.nullconversion.Address;
+import com.baeldung.nullconversion.Delivery;
+import com.baeldung.nullconversion.Person;
+import com.baeldung.nullconversion.ZipCode;
+import java.util.Optional;
+
+public class OnePersonOptionalDeliveryService extends MockOnePersonDeliveryServiceBase {
+
+
+    public OnePersonOptionalDeliveryService(Person person) {
+        super(person);
+    }
+
+    @Override
+    public Delivery calculateDeliveryForPerson(Long id) {
+        return Optional.ofNullable(getPersonById(id))
+          .map(Person::getAddress)
+          .map(Address::getZipCode)
+          .map(ZipCode::getCode)
+          .map(this::calculateDeliveryForZipCode)
+          .orElse(null);
+    }
+
+}