I have a simple model class Product
which exhibits a many to one relationship with ProductCategory
:
Product class:
@Entity
@Table(name="product")
public class Product {
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="id")
private Long id;
@Column(name="name")
private String name;
@Column(name="description")
private String description;
@ManyToOne(fetch=FetchType.LAZY)
@JoinColumn(name="category_id")
private ProductCategory category;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPdfUrl() {
return pdfUrl;
}
public void setPdfUrl(String pdfUrl) {
this.pdfUrl = pdfUrl;
}
public ProductCategory getCategory() {
return category;
}
public void setCategoryId(ProductCategory category) {
this.category = category;
}
}
ProductCategory class
@Entity
@Table(name="product_category",uniqueConstraints={@UniqueConstraint(columnNames="name")})
public class ProductCategory {
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="id")
private Long id;
@Column(name="name")
private String name;
@OneToMany(fetch=FetchType.LAZY, mappedBy="category")
private Set<Product> products = new HashSet<Product>(0);
// getters() & setters()
}
I am using Spring boot with Thymeleaf to create the necessary forms for the usual CRUD operations.
Here is the essential portion of my html page which I use to add a new Product
object into the database.
<form action="#" th:action="/product/save" th:object="${newProduct}" method="POST">
<input type="text" th:field="*{name}" />
<input type="text" th:field="*{description}" />
<select th:field="*{category}">
<option th:each="category: ${productCategories}" th:value="${category}" th:text="${category.name}" />
</select>
<button type="submit">Submit</button>
</form>
The problem is, when I try and insert the resulting Product
object from the controller (I know I haven't shown it here, mostly because I don't think that is actually the cause of the problem), there is a
MySQLIntegrityConstraintViolationException: Column 'category_id' cannot be null
I have tried changing the value
of the option
to ${category.id}
, but even that doesn't fix it.
How do I actually pass a complex object as a POST parameter into a controller using Thymeleaf?
Contrary to my first thoughts, this might actually be related to my Controller
, so here is my ProductController
:
@RequestMapping(value="/product/save", method=RequestMethod.POST)
public String saveProduct(@Valid @ModelAttribute("newProduct") Product product, ModelMap model) {
productRepo.save(product);
model.addAttribute("productCategories", productCategoryRepo.findAll());
return "admin-home";
}
@RequestMapping(value="/product/save")
public String addProduct(ModelMap model) {
model.addAttribute("newProduct", new Product());
model.addAttribute("productCategories", productCategoryRepo.findAll());
return "add-product";
}
Note that I have changed the form method to POST.
From thymeleafs perspective I can assure the below code should work.
<form method="POST" th:action="@{/product/save}" th:object="${newProduct}">
....
<select th:field="*{category}" class="form-control">
<option th:each="category: ${productCategories}" th:value="${category.id}" th:text="${category.name}"></option>
</select>
Provided that your controller looks like this.
@RequestMapping(value = "/product/save")
public String create(Model model) {
model.addAttribute("productCategories", productCategoryService.findAll());
model.addAttribute("newproduct", new Product()); //or try to fetch an existing object
return '<your view path>';
}
@RequestMapping(value = "/product/save", method = RequestMethod.POST)
public String create(Model model, @Valid @ModelAttribute("newProduct") Product newProduct, BindingResult result) {
if(result.hasErrors()){
//error handling
....
}else {
//or calling the repository to save the newProduct
productService.save(newProduct);
....
}
}
Update
Your models should have proper getters and setters with the correct names. For example, for the property category
You should have,
public ProductCategory getCategory(){
return category;
}
public void setCategory(productCategory category){
this.category = category;
}
NOTE - I have not compiled this code, I got it extracted from my current working project and replace the names with your class names
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With