Merge pull request #1 from KrishnaBishowkarma/working

refactor: Organize CRUD operations in N-tier architecture

src/main/java/com/krishna/Main.java

@@ -0,0 +1,14 @@
+package com.krishna;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+
+public class Main {
+
+    public static void main(String[] args) {
+        SpringApplication.run(Main.class, args);
+    }
+
+}

src/main/java/com/krishna/customer/Customer.java

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+package com.krishna.customer;
+
+import java.util.Objects;
+
+public class Customer {
+    private Integer id;
+    private String name;
+    private String email;
+    private Integer age;
+
+    public Customer() {
+    }
+
+    public Customer(Integer id, String name, String email, Integer age) {
+        this.id = id;
+        this.name = name;
+        this.email = email;
+        this.age = age;
+    }
+
+    public Integer getId() {
+        return id;
+    }
+
+    public void setId(Integer id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getEmail() {
+        return email;
+    }
+
+    public void setEmail(String email) {
+        this.email = email;
+    }
+
+    public Integer getAge() {
+        return age;
+    }
+
+    public void setAge(Integer age) {
+        this.age = age;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Customer customer = (Customer) o;
+        return Objects.equals(id, customer.id) && Objects.equals(name, customer.name) && Objects.equals(email, customer.email) && Objects.equals(age, customer.age);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(id, name, email, age);
+    }
+
+    @Override
+    public String toString() {
+        return "Customer{" +
+                "id=" + id +
+                ", name='" + name + '\'' +
+                ", email='" + email + '\'' +
+                ", age=" + age +
+                '}';
+    }
+}

src/main/java/com/krishna/customer/CustomerController.java

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+package com.krishna.customer;
+
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.util.List;
+
+@RestController
+public class CustomerController {
+
+    private final CustomerService customerService;
+
+
+    public CustomerController(CustomerService customerService) {
+        this.customerService = customerService;
+    }
+
+    /*
+    @RequestMapping(value = "api/v1/customers",
+            method = RequestMethod.GET
+    )
+    This is the same as below :
+    */
+
+    @GetMapping("api/v1/customers")
+    public List<Customer> getCustomers() {
+        return customerService.getAllCustomers();
+    }
+
+    @GetMapping("api/v1/customers/{customerId}")
+    public Customer getCustomer(
+            @PathVariable("customerId") Integer customerId) {
+        return customerService.getCustomer(customerId);
+    }
+}

src/main/java/com/krishna/customer/CustomerDao.java

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+package com.krishna.customer;
+
+import java.util.List;
+import java.util.Optional;
+
+public interface CustomerDao {
+    List<Customer> selectAllCustomers();
+    Optional<Customer> selectCustomerById(Integer id);
+}

src/main/java/com/krishna/customer/CustomerDataAccessService.java

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+package com.krishna.customer;
+
+import org.springframework.stereotype.Repository;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+
+@Repository
+public class CustomerDataAccessService implements CustomerDao {
+
+    //db
+    private static List<Customer> customers;
+
+    static {
+        customers = new ArrayList<>();
+        Customer krishna = new Customer(
+                1,
+                "Krishna",
+                "[email protected]",
+                25
+        );
+        customers.add(krishna);
+
+        Customer janaki = new Customer(
+                2,
+                "Janaki",
+                "[email protected]",
+                28
+        );
+        customers.add(janaki);
+    }
+
+    @Override
+    public List<Customer> selectAllCustomers() {
+        return customers;
+    }
+
+    @Override
+    public Optional<Customer> selectCustomerById(Integer id) {
+        return customers.stream()
+                .filter(c -> c.getId().equals(id))
+                .findFirst();
+    }
+}

src/main/java/com/krishna/customer/CustomerService.java

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+package com.krishna.customer;
+
+import org.springframework.stereotype.Service;
+
+import java.util.List;
+
+@Service
+public class CustomerService {
+
+    private final CustomerDao customerDao;
+
+    public CustomerService(CustomerDao customerDao) {
+        this.customerDao = customerDao;
+    }
+
+    public List<Customer> getAllCustomers() {
+        return customerDao.selectAllCustomers();
+    }
+
+    public Customer getCustomer(Integer id) {
+        return customerDao.selectCustomerById(id)
+                .orElseThrow(() -> new IllegalArgumentException("Customer with [%s] not found".formatted(id)));
+    }
+}