如何在 SpringMvc 的 @JoinColumn 中插入数据

Question

I have two tables CustomerDetails and Product , I want to fetch customerid from customer table and add it to @joincolumn(order_id) column in same CustomerDetails table.

CustomerDetails.java

@Entity
@Table(name = "CustomerDetails")
public class CustomerDetails {

    @Id
    @GeneratedValue
    @Column(name="CUSTOMER_ID")
    private Long custid;

    @Column(name="CUSTOMER_NAME")
    private String customerName;
    
    @Column(name="EMAIL")
    private String email;
    
    @Column(name="ADDRESS")
    private String address;
    
    @Column(name="PHONENO")
    private String phoneno;
    
    public CustomerDetails() {
    }

    @Override
    public String toString() {
        return "CustomerDetails [custid=" + custid + ", customername=" + customerName + ", email=" + email
                + ", address=" + address + ", phoneno=" + phoneno + "]";
    }

    public CustomerDetails(String customername, String email, String address, String phoneno) {
        super();
        this.customerName = customername;
        this.email = email;
        this.address = address;
        this.phoneno = phoneno;
    }   
    public Long getCustid() {
        return custid;
    }

    public void setCustid(Long custid) {
        this.custid = custid;
    }

    public String getName() {
        return customerName;
    }

    public void setName(String name) {
        this.customerName = name;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getPassword() {
        return address;
    }

    public void setPassword(String password) {
        this.address = password;
    }

    public String getPhoneno() {
        return phoneno;
    }

    public void setPhoneno(String phoneno) {
        this.phoneno = phoneno;
    }   
}

Product.java

@Entity
@Table(name="Product")
public class Product {
    
    @Id
    @GeneratedValue
    @Column(name="PRODUCT_ID")
    private Long productId;
    
    @Column(name="PRODUCT_NAME")
    private String productName;
    
    @Column(name="PRODUCT_BRAND")
    private String productBrand;
    
    @Column(name="PRODUCT_PRICE")
    private double productPrice;
    
    @OneToOne
    private CustomerDetails cd;
   
    public Product(Long productId, String productName, String productBrand, double productPrice, CustomerDetails cd) {
        super();
        this.productId = productId;
        this.productName = productName;
        this.productBrand = productBrand;
        this.productPrice = productPrice;
        this.cd = cd;
    }
    
    public Product(String productName, String productType, double productPrice) {
        super();
        this.productName = productName;
        this.productBrand = productType;
        this.productPrice = productPrice;
    }
    
    public Long getProductId() {
        return productId;
    }
    public void setProductId(Long productId) {
        this.productId = productId;
    }
    public String getProductName() {
        return productName;
    }
    public void setProductName(String productName) {
        this.productName = productName;
    }
    public String getProductBrand() {
        return productBrand;
    }
    public void setProductBrand(String productType) {
        this.productBrand = productType;
    }
    public double getProductPrice() {
        return productPrice;
    }
    public void setProductPrice(double productPrice) {
        this.productPrice = productPrice;
    }
    
    public CustomerDetails getCd() {
        return cd;
    }

    public void setCd(CustomerDetails cd) {
        this.cd = cd;
    }
    public Product() {
        //super();
    }
    @Override
    public String toString() {
        return "Product [productId=" + productId + ", productName=" + productName + ", productType=" + productBrand
                + ", productPrice=" + productPrice + "]";
    }
 
}

CustomerDetails repository

@Repository
public interface CdRepo extends JpaRepository<CustomerDetails, Long>
{
            
}

Product repository

@Repository
public interface ProductRepo extends JpaRepository<Product, Long>
{
        
}

CustomerService

@Service
@Transactional
public class CustomerService  {
    
    private final CdRepo cdRepo;
    
    @Autowired
    public CustomerService(CdRepo cdRepo) {
        
        this.cdRepo = cdRepo;
        
    }
    public void saveCustomer(CustomerDetails cd) 
    {
        cdRepo.save(cd);
            
    }   
}

controller

@RequestMapping(value = {"/addCustomerDetails"}, method = RequestMethod.POST)
    public ModelAndView addCustomerDetails(CustomerDetails cd) 
    {
        
        customerService.saveCustomer(cd);
        System.out.println(cd.getCustid());
        ModelAndView model = new ModelAndView();
        model.setViewName("homepage");
        return model;
    }

In controller using getCustid() I'm getting current customer's id now I want to insert that id into @joinColumn(order_id)

Answer 1

If I've understood correctly, you want to assign a product to a user (eg Customer). For a @OneToOne relation you don't need private CustomerDetails cd; in product class. Although I don't know why are you implementing such thing in that way at all!

Generally If you want to assign two things together, let's say you want to assign a product to a user so that the product would be for that user, you should find the product obj from repository or any where (both product and user must have an id generated by db) and then assign it to user.product .

product service

@Service
public class ProductService  {

  @Autowired
  private ProductRepo productRepository;

  public Optional<Product> findProductById(Long id) {
     return this.productRepository.findByProductId(id);
  }  

}

customer service

@Service
@Transactional
public class CustomerService  {

  private final CdRepo cdRepo;

  @Autowired
  public CustomerService(CdRepo cdRepo) {
    this.cdRepo = cdRepo;
  }

  public CustomerDetails saveCustomer(CustomerDetails cd, Long productId) {
    CustomerDetails dbCustomer = customerService.saveCustomer(cd);
    // I'm getting the id from path variable, change it if you have other logics
    Optional<Product> dbProduct = this.productService.findProductById(productId);
    // I don't know how you handle run time errors so I can't write it, don't
    // forget to check the dbProduct in case it didn't exist :)
    
    // In case you did not created getters and setters in CustomerDetails,
    // use dbCustomer.product = dbProduct.get();
    dbCustomer.setProduct(dbProduct.get());

    // update our customer using JPA, after customer update JPA handles everything
    return this.cdRepo.save(dbCustomer);
        
  }  

}

controller

@RequestMapping(value = {"/addCustomerDetails/{productId}"}, method = RequestMethod.POST)
public ModelAndView addCustomerDetails(CustomerDetails cd, @PathVariable Long productId ) 
{
    
    CustomerDetails dbCustomer = this.customerService.saveCustomer(cd, productId);
    // Use the dbCustomer in your logic ...
    ModelAndView model = new ModelAndView();
    model.setViewName("homepage");
    return model;
}

Write getters and setters in each entity or use Lombok annotation @Data . Usually when I want to deploy an ecommerce with user and product. I use user , cart , product model.

The problem with the code above is that if you assign that product to a user, it's ONLY for that user. if other users want the same product you have to create all of those products for them. Solution to that would be using product as a series or a model.

Imagine a situation that you want to create a website to sell coffee packages. you only have two type of package to sell. you can create an entity like product for those packages with a quantity for each. Then create a @OneToMany relationship in your cart model to products. It will create a join table to store any possible product id there with cart id. After that, create a @ManyToOne relationship in your cart entity and @OneToMany in your user entity. Now each cart is only for a specific user and not the products.

Some Friendly Advice:

• Don't populate your controller with logic. Let service layer handle it.
• For each entity, create a package with the name of the entity instead and create 3 classes; the entity itself, response POJO and request POJO.
• Use getters and setters for your entites. You can use lombok for that matter. It will handle the situation by generating them.
• Use convertor components to create and convert requested entity to the entity itself and also convert entity to response entity.
• Avoid interacting with Data base as much as you can. hold the object in a variable like dbCustomer for doing operations.