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alejandrogervasioKevinGilmore
alejandrogervasio
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KevinGilmore
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BAEL-2789 - The Dependency Inversion Principle in Java (eugenp#6613)
* Initial Commit * Added dip dipmodular modules to pom.xml * Delete pom.xml * Add pom.xml * Update pom.xml * Update pom.xml * Update pom.xml * Update Application.java * Update CustomerDaoUnitTest.java * Update CustomerServiceUnitTest.java * Update Application.java * Update CustomerDaoUnitTest.java * Update CustomerServiceUnitTest.java * Update CustomerDaoUnitTest.java * Update CustomerServiceUnitTest.java
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-3
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9 files changed

+236
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‎patterns/dip/pom.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<groupId>com.baeldung.dip</groupId>
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<artifactId>dip</artifactId>
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<name>dip</name>
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<version>1.0-SNAPSHOT</version>
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<parent>
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<groupId>com.baeldung</groupId>
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<artifactId>patterns</artifactId>
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<version>1.0.0-SNAPSHOT</version>
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<relativePath>..</relativePath>
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</parent>
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<dependencies>
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<dependency>
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<groupId>junit</groupId>
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<artifactId>junit</artifactId>
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<version>4.12</version>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.assertj</groupId>
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<artifactId>assertj-core</artifactId>
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<version>3.12.1</version>
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<scope>test</scope>
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</dependency>
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</dependencies>
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<properties>
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<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
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<maven.compiler.source>11</maven.compiler.source>
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<maven.compiler.target>11</maven.compiler.target>
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</properties>
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</project>

‎patterns/dip/src/main/java/com/baeldung/dip/application/Application.java‎

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package com.baeldung.dip.application;
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import com.baeldung.dip.daoimplementations.SimpleCustomerDao;
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import com.baeldung.dip.entities.Customer;
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import com.baeldung.dip.services.CustomerService;
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import java.util.Map;
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import java.util.HashMap;
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public class Application {
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public static void main(String[] args) {
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Map<Integer, Customer> customers = new HashMap<>();
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customers.put(1, new Customer("John"));
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customers.put(2, new Customer("Susan"));
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CustomerService customerService = new CustomerService(new SimpleCustomerDao(customers));
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customerService.findAll().forEach(System.out::println);
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}
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}

‎patterns/dip/src/main/java/com/baeldung/dip/daoimplementations/SimpleCustomerDao.java‎

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package com.baeldung.dip.daoimplementations;
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import com.baeldung.dip.entities.Customer;
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import com.baeldung.dip.daointerfaces.CustomerDao;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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import java.util.Optional;
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public class SimpleCustomerDao implements CustomerDao {
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private Map<Integer, Customer> customers = new HashMap<>();
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public SimpleCustomerDao(Map<Integer, Customer> customers) {
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this.customers = customers;
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}
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@Override
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public Optional<Customer> findById(int id) {
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return Optional.ofNullable(customers.get(id));
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}
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@Override
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public List<Customer> findAll() {
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return new ArrayList<>(customers.values());
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}
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}

‎patterns/dip/src/main/java/com/baeldung/dip/daointerfaces/CustomerDao.java‎

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package com.baeldung.dip.daointerfaces;
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import com.baeldung.dip.entities.Customer;
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import java.util.List;
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import java.util.Optional;
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public interface CustomerDao {
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Optional<Customer> findById(int id);
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List<Customer> findAll();
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}

‎patterns/dip/src/main/java/com/baeldung/dip/entities/Customer.java‎

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package com.baeldung.dip.entities;
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public class Customer {
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private final String name;
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public Customer(String name) {
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this.name = name;
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}
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public String getName() {
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return name;
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}
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@Override
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public String toString() {
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return "Customer{" + "name=" + name + '}';
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}
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}

‎patterns/dip/src/main/java/com/baeldung/dip/services/CustomerService.java‎

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package com.baeldung.dip.services;
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import com.baeldung.dip.daointerfaces.CustomerDao;
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import com.baeldung.dip.entities.Customer;
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import java.util.List;
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import java.util.Optional;
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public class CustomerService {
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private final CustomerDao customerDao;
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public CustomerService(CustomerDao customerDao) {
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this.customerDao = customerDao;
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}
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public Optional<Customer> findById(int id) {
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return customerDao.findById(id);
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}
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public List<Customer> findAll() {
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return customerDao.findAll();
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}
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}

‎patterns/dip/src/test/java/com/baeldung/dip/tests/CustomerDaoUnitTest.java‎

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package com.baeldung.dip.tests;
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import com.baeldung.dip.daoimplementations.SimpleCustomerDao;
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import com.baeldung.dip.daointerfaces.CustomerDao;
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import com.baeldung.dip.entities.Customer;
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import java.util.Map;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Optional;
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import static org.assertj.core.api.Assertions.assertThat;
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import org.junit.Before;
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import org.junit.Test;
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public class CustomerDaoUnitTest {
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private CustomerDao customerDao;
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@Before
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public void setUpCustomerDaoInstance() {
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Map<Integer, Customer> customers = new HashMap<>();
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customers.put(1, new Customer("John"));
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customers.put(2, new Customer("Susan"));
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customerDao = new SimpleCustomerDao(customers);
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}
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@Test
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public void givenCustomerDaoInstance_whenCalledFindById_thenCorrect() {
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assertThat(customerDao.findById(1)).isInstanceOf(Optional.class);
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}
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@Test
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public void givenCustomerDaoInstance_whenCalledFindAll_thenCorrect() {
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assertThat(customerDao.findAll()).isInstanceOf(List.class);
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}
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@Test
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public void givenCustomerDaoInstance_whenCalledFindByIdWithNullCustomer_thenCorrect() {
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Map<Integer, Customer> customers = new HashMap<Integer, Customer>();
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customers.put(1, null);
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CustomerDao customerDaoObject = new SimpleCustomerDao(customers);
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Customer customer = customerDaoObject.findById(1).orElseGet(() -> new Customer("Non-existing customer"));
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assertThat(customer.getName()).isEqualTo("Non-existing customer");
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}
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}

‎patterns/dip/src/test/java/com/baeldung/dip/tests/CustomerServiceUnitTest.java‎

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package com.baeldung.dip.tests;
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import com.baeldung.dip.daoimplementations.SimpleCustomerDao;
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import com.baeldung.dip.entities.Customer;
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import com.baeldung.dip.services.CustomerService;
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import java.util.Map;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Optional;
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import static org.assertj.core.api.Assertions.assertThat;
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import org.junit.Before;
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import org.junit.Test;
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public class CustomerServiceUnitTest {
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private CustomerService customerService;
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@Before
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public void setUpCustomerServiceInstance() {
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Map<Integer, Customer> customers = new HashMap<>();
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customers.put(1, new Customer("John"));
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customers.put(2, new Customer("Susan"));
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customerService = new CustomerService(new SimpleCustomerDao(customers));
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}
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@Test
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public void givenCustomerServiceInstance_whenCalledFindById_thenCorrect() {
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assertThat(customerService.findById(1)).isInstanceOf(Optional.class);
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}
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@Test
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public void givenCustomerServiceInstance_whenCalledFindAll_thenCorrect() {
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assertThat(customerService.findAll()).isInstanceOf(List.class);
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}
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@Test
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public void givenCustomerServiceInstance_whenCalledFindByIdWithNullCustomer_thenCorrect() {
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Map<Integer, Customer> customers = new HashMap<>();
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customers.put(1, null);
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customerService = new CustomerService(new SimpleCustomerDao(customers));
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Customer customer = customerService.findById(1).orElseGet(() -> new Customer("Non-existing customer"));
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assertThat(customer.getName()).isEqualTo("Non-existing customer");
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}
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}

‎patterns/pom.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<artifactId>patterns</artifactId>
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<packaging>pom</packaging>
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<name>patterns</name>
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<name>patterns</name>
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<parent>
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<groupId>com.baeldung</groupId>
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<module>design-patterns</module>
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<module>design-patterns-2</module>
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<module>solid</module>
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<module>dip</module>
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</modules>
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<dependencyManagement>
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<jetty-maven-plugin.version>9.4.0.v20161208</jetty-maven-plugin.version>
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</properties>
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</project>
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</project>

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