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Inventory Item Entity

Purpose: Represents individual products/items in inventory with stock tracking

Database Table: INVENTORY_ITEM

Entity Definition

@Entity
@Table(name = "INVENTORY_ITEM")
@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
public class InventoryItem {
    
    @Id
    @Column(name = "ID", nullable = false)
    private String id;  // UUID
    
    @Column(name = "NAME", nullable = false, unique = true)
    private String name;  // Unique item name
    
    @Column(name = "SKU")
    private String sku;  // Stock keeping unit
    
    @Column(name = "SUPPLIER_ID", nullable = false)
    private String supplierId;  // Foreign key to SUPPLIER
    
    @ManyToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "SUPPLIER_ID", insertable = false, updatable = false)
    private Supplier supplier;  // Relationship object (eagerly loaded)
    
    @Column(name = "QUANTITY", nullable = false)
    private int quantity;  // Current stock quantity
    
    @Column(name = "UNIT_PRICE", nullable = false)
    private BigDecimal unitPrice;  // Cost per unit
    
    @Column(name = "CREATED_BY", nullable = false)
    private String createdBy;
    
    @CreationTimestamp
    @Column(name = "CREATED_AT", nullable = false, updatable = false)
    private LocalDateTime createdAt;
    
    @Version  // Optimistic locking
    @Column(name = "VERSION")
    private Long version;  // Incremented on updates
}

Business Rules

1. Unique Name: Item name must be unique within system
2. Valid Supplier: Item must reference an existing supplier
3. Non-Negative Quantity: Stock quantity must be >= 0
4. Non-Negative Price: Unit price must be >= 0
5. Deletion Policy: Item cannot be deleted if stock > 0 (business policy)
6. Audit Trail: Every stock change creates entry in STOCK_HISTORY
7. Immutable Creation: createdAt and createdBy fields cannot be updated

Key Features

• Optimistic Locking: Version field prevents concurrent modification conflicts
  • Hibernate automatically increments on each update
  • Throws OptimisticLockException if stale data detected
• Eager Supplier Loading: Supplier always loaded with item (eliminates N+1 query problems)
• Immutable Timestamps: createdAt and createdBy protected with updatable = false

Key Relationships

• Many-to-One with Supplier: Many items belong to one supplier
• One-to-Many with StockHistory: One item can have multiple stock history entries (audit trail)

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