BAEL-2789 - The Dependency Inversion Principle in Java (#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
2019-03-30 13:01:00 -03:00
parent 86bded12be
commit b67a006020
9 changed files with 236 additions and 3 deletions
@@ -0,0 +1,18 @@
+package com.baeldung.dip.application;
+
+import com.baeldung.dip.daoimplementations.SimpleCustomerDao;
+import com.baeldung.dip.entities.Customer;
+import com.baeldung.dip.services.CustomerService;
+import java.util.Map;
+import java.util.HashMap;
+
+public class Application {
+
+    public static void main(String[] args) {
+        Map<Integer, Customer> customers = new HashMap<>();
+        customers.put(1, new Customer("John"));
+        customers.put(2, new Customer("Susan"));
+        CustomerService customerService = new CustomerService(new SimpleCustomerDao(customers));
+        customerService.findAll().forEach(System.out::println);
+    }
+}
@@ -0,0 +1,28 @@
+package com.baeldung.dip.daoimplementations;
+
+import com.baeldung.dip.entities.Customer;
+import com.baeldung.dip.daointerfaces.CustomerDao;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+
+public class SimpleCustomerDao implements CustomerDao {
+
+    private Map<Integer, Customer> customers = new HashMap<>();
+
+    public SimpleCustomerDao(Map<Integer, Customer> customers) {
+        this.customers = customers;
+    }
+
+    @Override
+    public Optional<Customer> findById(int id) {
+        return Optional.ofNullable(customers.get(id));
+    }
+
+    @Override
+    public List<Customer> findAll() {
+        return new ArrayList<>(customers.values());
+    }
+}
@@ -0,0 +1,13 @@
+package com.baeldung.dip.daointerfaces;
+
+import com.baeldung.dip.entities.Customer;
+import java.util.List;
+import java.util.Optional;
+
+public interface CustomerDao {
+
+    Optional<Customer> findById(int id);
+
+    List<Customer> findAll();
+
+}
@@ -0,0 +1,19 @@
+package com.baeldung.dip.entities;
+
+public class Customer {
+
+    private final String name;
+
+    public Customer(String name) {
+        this.name = name;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    @Override
+    public String toString() {
+        return "Customer{" + "name=" + name + '}';
+    }
+}
@@ -0,0 +1,23 @@
+package com.baeldung.dip.services;
+
+import com.baeldung.dip.daointerfaces.CustomerDao;
+import com.baeldung.dip.entities.Customer;
+import java.util.List;
+import java.util.Optional;
+
+public class CustomerService {
+
+    private final CustomerDao customerDao;
+
+    public CustomerService(CustomerDao customerDao) {
+        this.customerDao = customerDao;
+    }
+
+    public Optional<Customer> findById(int id) {
+        return customerDao.findById(id);
+    }
+
+    public List<Customer> findAll() {
+        return customerDao.findAll();
+    }
+}
@@ -0,0 +1,46 @@
+package com.baeldung.dip.tests;
+
+import com.baeldung.dip.daoimplementations.SimpleCustomerDao;
+import com.baeldung.dip.daointerfaces.CustomerDao;
+import com.baeldung.dip.entities.Customer;
+import java.util.Map;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Optional;
+import static org.assertj.core.api.Assertions.assertThat;
+import org.junit.Before;
+import org.junit.Test;
+
+public class CustomerDaoUnitTest {
+
+    private CustomerDao customerDao;
+
+    @Before
+    public void setUpCustomerDaoInstance() {
+        Map<Integer, Customer> customers = new HashMap<>();
+        customers.put(1, new Customer("John"));
+        customers.put(2, new Customer("Susan"));
+        customerDao = new SimpleCustomerDao(customers);
+    }
+
+    @Test
+    public void givenCustomerDaoInstance_whenCalledFindById_thenCorrect() {
+        assertThat(customerDao.findById(1)).isInstanceOf(Optional.class);
+    }
+
+    @Test
+    public void givenCustomerDaoInstance_whenCalledFindAll_thenCorrect() {
+        assertThat(customerDao.findAll()).isInstanceOf(List.class);
+    }
+
+    @Test
+    public void givenCustomerDaoInstance_whenCalledFindByIdWithNullCustomer_thenCorrect() {
+        Map<Integer, Customer> customers = new HashMap<Integer, Customer>();
+        customers.put(1, null);
+        CustomerDao customerDaoObject = new SimpleCustomerDao(customers);
+
+        Customer customer = customerDaoObject.findById(1).orElseGet(() -> new Customer("Non-existing customer"));
+
+        assertThat(customer.getName()).isEqualTo("Non-existing customer");
+    }
+}
@@ -0,0 +1,46 @@
+package com.baeldung.dip.tests;
+
+import com.baeldung.dip.daoimplementations.SimpleCustomerDao;
+import com.baeldung.dip.entities.Customer;
+import com.baeldung.dip.services.CustomerService;
+import java.util.Map;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Optional;
+import static org.assertj.core.api.Assertions.assertThat;
+import org.junit.Before;
+import org.junit.Test;
+
+public class CustomerServiceUnitTest {
+
+    private CustomerService customerService;
+
+    @Before
+    public void setUpCustomerServiceInstance() {
+        Map<Integer, Customer> customers = new HashMap<>();
+        customers.put(1, new Customer("John"));
+        customers.put(2, new Customer("Susan"));
+        customerService = new CustomerService(new SimpleCustomerDao(customers));
+    }
+
+    @Test
+    public void givenCustomerServiceInstance_whenCalledFindById_thenCorrect() {
+        assertThat(customerService.findById(1)).isInstanceOf(Optional.class);
+    }
+
+    @Test
+    public void givenCustomerServiceInstance_whenCalledFindAll_thenCorrect() {
+        assertThat(customerService.findAll()).isInstanceOf(List.class);
+    }
+
+    @Test
+    public void givenCustomerServiceInstance_whenCalledFindByIdWithNullCustomer_thenCorrect() {
+        Map<Integer, Customer> customers = new HashMap<>();
+        customers.put(1, null);
+        customerService = new CustomerService(new SimpleCustomerDao(customers));
+
+        Customer customer = customerService.findById(1).orElseGet(() -> new Customer("Non-existing customer"));
+
+        assertThat(customer.getName()).isEqualTo("Non-existing customer");
+    }
+}