added comment on the class level

src/main/java/com/ecom/common/EcomUtils.java

 package com.ecom.common;
 
+/**
+ * Utility class
+ */
 public interface EcomUtils {
     String ERROR_IN_DB="Some error in DB could not process your order";
     String SUCCESS_MESSAGE = "Order Placed...!  you have spent :";

src/main/java/com/ecom/controller/ItemController.java

@@ -11,6 +11,9 @@ import org.springframework.web.bind.annotation.*;
 import java.util.List;
 import java.util.Optional;
 
+/**
+ * Item related CRUD OPERATION
+ */
 @RestController
 @RequestMapping("item")
 @Slf4j

src/main/java/com/ecom/controller/OrderController.java

@@ -10,6 +10,9 @@ import org.springframework.web.bind.annotation.*;
 
 import java.util.List;
 
+/**
+ * ORDER RELATED CRUD OPERATION AND ORDER PROCESS CONTROLLER
+ */
 @RestController
 @RequestMapping("order")
 @Slf4j

src/main/java/com/ecom/model/OrderedItems.java

@@ -7,6 +7,9 @@ import javax.persistence.GeneratedValue;
 import javax.persistence.GenerationType;
 import javax.persistence.Id;
 
+/**
+ * ORDER DETAILS HAS EACH ITEM RELATED INFO
+ */
 @Data
 @NoArgsConstructor
 @Entity

src/main/java/com/ecom/model/Orders.java

@@ -6,6 +6,10 @@ import lombok.NoArgsConstructor;
 import javax.persistence.*;
 import java.util.List;
 
+/**
+ * ACTUAL ORDER PLACED PER UER
+ * also  //used hibernate one-to-many mapping
+ */
 @Data
 @Entity
 @NoArgsConstructor
@@ -13,6 +17,8 @@ public class Orders {
     @Id
     @GeneratedValue(strategy = GenerationType.AUTO)
     private int orderId;
+
+    //using hibernate one-to-many mapping
     @OneToMany(targetEntity = OrderedItems.class,cascade = CascadeType.ALL)
     @JoinColumn(name = "orderId",referencedColumnName = "orderId")
     private List<OrderedItems> orderedItems;

src/main/java/com/ecom/repository/ItemRepository.java

 package com.ecom.repository;
 
 import com.ecom.model.Item;
+import org.hibernate.validator.constraints.pl.REGON;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.stereotype.Repository;
 
+/**
+ * SAVING DATA TO DB
+ */
+@Repository
 public interface ItemRepository  extends JpaRepository<Item,Integer> {
 }

src/main/java/com/ecom/repository/OrderRepository.java

@@ -2,9 +2,14 @@ package com.ecom.repository;
 
 import com.ecom.model.Orders;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.stereotype.Repository;
 
 import java.util.List;
 
+/**
+ * saving order data to db
+ */
+@Repository
 public interface OrderRepository  extends JpaRepository<Orders, Integer> {
     List<Orders> findByEmailId(String emailId);
 }

src/main/java/com/ecom/repository/OrderedItemsRepository.java

@@ -2,7 +2,12 @@ package com.ecom.repository;
 
 import com.ecom.model.OrderedItems;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.stereotype.Repository;
 
+/**
+ * SAVING DATA TO DB
+ */
+@Repository
 public interface OrderedItemsRepository extends JpaRepository<OrderedItems,Integer> {
 
 }

src/main/java/com/ecom/service/impl/ItemServiceImpl.java

@@ -10,6 +10,9 @@ import org.springframework.stereotype.Service;
 import java.util.List;
 import java.util.Optional;
 
+/**
+ * Item related service Basic CRUD OPERATION
+ */
 @Service
 @Slf4j
 public class ItemServiceImpl  implements ItemService {

src/main/java/com/ecom/service/impl/OrderServiceImpl.java

@@ -15,6 +15,9 @@ import org.springframework.stereotype.Service;
 import java.util.List;
 import java.util.Optional;
 
+/**
+ * Actual Business logic for Processing the order and fetching the order details
+ */
 @Service
 @Slf4j
 public class OrderServiceImpl implements OrderService {