Question

I’m using Spring 3.1.1.RELEASE. I have this command object …

@Entity
public class Contract {

    @Id
        @Column(name = "ID")
        @GeneratedValue(strategy=GenerationType.AUTO)
        private Integer id;

        @OneToOne(fetch = FetchType.EAGER, targetEntity = Product.class)
        @JoinColumn(name = "PRODUCT_ID")
        @NotNull
        private Product product;

        @Column(name = "ORDER_ID")
        @NotNull
        private String orderId;     
    …

and what I want on my JSP form is to have a drop down list of products represent the product field. Once a user selects one and submits the form, it would populate the object’s “product” member field through the command object’s setProduct method. I know how to set up the String fields,

<form:input path="orderId" />

but what do I need to put in my controller and JSP so that when my request is submitted to the controller …

@RequestMapping(value = "/add", method = RequestMethod.POST)
public ModelAndView addContract(final Contract contract,
                                final BindingResult result) {
…

the Product field will be populated correctly?

Answer 1

The answer involved a little more than just the JSP select tag. It also required binders. If I have this class

@Component
public class ProductEditor extends PropertyEditorSupport
{

    @Autowired
    private ProductService m_productSvc;

    @Override
    public String getAsText()
    {
        final Product product = (Product) getValue();
        final String text = (product != null ? product.getProductId() : "");
        return text;
    }

    @Override
    public void setAsText(final String id)
    {
        final Product product = m_productSvc.findById(id);
        setValue(product);
    }
}

I can register the binder in my controller …

    @InitBinder
    public void initBinder(WebDataBinder binder) {
        …
        binder.registerCustomEditor(Product.class, this.m_productEditor);
    }

Then in my JSP, I can have

                <form:select path="product">
                    <form:option value="" label="Select" />
                    <form:options items="${productList}" itemValue="id" itemLabel="name" />
                </form:select>

and my selection will be bound to the “product” field of my command object.