问题描述
我是JSF的新手，我一直试图从使用h：selectOneMenu的表单中存储数据来获取产品的类别。 h：selectOneMenu正在从DB填充，但是，当尝试在DB中存储产品时，我收到一个错误：转换错误设置值'52'表示'null Converter'。我已经在线查看了StackOverflow和教程中的类似问题，但我仍然收到错误。
I'm new to JSF and I have been trying to store data from a form that uses a h:selectOneMenu to get the category of a product. The h:selectOneMenu is being populated from the DB, however, when trying to store a product in the DB, I am getting an error: Conversion Error setting value '52' for 'null Converter'. I have reviewed similar problems in StackOverflow and tutorials online but I am still getting the error.
这是xhtml：
<h:selectOneMenu id="category_fk" value="#{productController.product.category_fk}"
converter="#{categoryConverter}" title="Category_fk" >
<!-- DONE: update below reference to list of available items-->
<f:selectItems value="#{productController.categoryList}" var="prodCat"
itemValue="#{prodCat}" itemLabel="#{prodCat.name}"/>
</h:selectOneMenu>
这是产品控制器：
@Named
@RequestScoped
public class ProductController {
@EJB
private ProductEJB productEjb;
@EJB
private CategoryEJB categoryEjb;
private Product product = new Product();
private List<Product> productList = new ArrayList<Product>();
private Category category;
private List<Category> categoryList = new ArrayList<Category>();
public String doCreateProduct()
{
product = productEjb.createProduct(product);
productList = productEjb.findAllProducts();
return "listProduct";
}
@PostConstruct
public void init()
{
categoryList = categoryEjb.findAllCategory();
productList = productEjb.findAllProducts();
}
// Getters/Setters and other methods omitted for simplicity
为简单起见，这是简化的EJB：
This is the EJB simplified for simplicity:
@Stateless
public class ProductEJB{
@PersistenceContext(unitName = "luavipuPU")
private EntityManager em;
public List<Product> findAllProducts()
{
TypedQuery<Product> query = em.createNamedQuery("findAllProducts", Product.class);
return query.getResultList();
}
public Product createProduct(Product product)
{
em.persist(product);
return product;
}
}
这是产品实体简化为简单：
This is the product Entity simplified for simplicity:
@Entity
@NamedQueries({
@NamedQuery(name="findAllProducts", query = "SELECT p from Product p")
})
public class Product implements Serializable
{
private static final long serialVersionUID = 1L;
@Id @GeneratedValue(strategy= GenerationType.AUTO)
private int product_id;
private String name;
private String description;
protected byte[] imageFile;
private Float price;
@Temporal(TemporalType.TIMESTAMP)
private Date dateAdded;
@ManyToOne
private Category category_fk;
@ManyToOne
private SaleDetails saleDetails_fk;
这是我正在使用的更新转换器：
This is the updated converter I am using:
@ManagedBean
@FacesConverter(value="categoryConverter")
public class CategoryConverter implements Converter{
@PersistenceContext
private transient EntityManager em;
@Override
public Object getAsObject(FacesContext context, UIComponent component, String value) {
return em.find(Category.class, new Integer(value));
}
@Override
public String getAsString(FacesContext context, UIComponent component, Object value) {
Category category;
category = (Category) value;
return String.valueOf(category.getCategory_id());
}
}
代码已包含已从Orignal问题更新，代码现在完美有效。
The code has been updated from the Orignal problem, the code perfectly works now.
推荐答案
您不能在<$上使用自定义类型c $ c>< h：selectOneMenu /> 组件（或任何< h：selectXXXX /> ）而不创建JSF 。转换器存在于JSF中，以帮助将基本上自定义或服务器端的项目/构造转换为网页友好/人类可读格式，并且还能够将选择从客户端保存回服务器端。那么错误消息本质上告诉你的是，它从客户端提交的值 52 中没有足够的意义将其作为<$保存到服务器端c $ c>类别对象/类型
You can't use a custom type on the <h:selectOneMenu/> component (or any of the <h:selectXXXX/>) without creating a JSF Converter. Converters exist in JSF to assist with translating essentially custom or sever-side items/constructs into web page friendly/human readable formats and also to be able to save selections from the client side back to the server side. So what the error message is essentially telling you there is that it cannot make sense enough of the value 52 submitted from the client side to save it to the server side as a Category object/type
所以你需要做的是创建一个JSF的实现转换器这实际上有助于JSF理解你的 Category 对象。
So what you're required to do is to create an implementation of a JSF converter that essentially helps JSF make sense of your Category object.
这里是粗略估计您需要做什么：
Here's a rough estimation of what you need to do:
-
为您的
类别实施转换器类型：
// You must annotate the converter as a managed bean, if you want to inject
// anything into it, like your persistence unit for example.
@ManagedBean(name = "categoryConverterBean")
@FacesConverter(value = "categoryConverter")
public class CategoryConverter implements Converter {
@PersistenceContext(unitName = "luavipuPU")
// I include this because you will need to
// lookup your entities based on submitted values
private transient EntityManager em;
@Override
public Object getAsObject(FacesContext ctx, UIComponent component,
String value) {
// This will return the actual object representation
// of your Category using the value (in your case 52)
// returned from the client side
return em.find(Category.class, new BigInteger(value));
}
@Override
public String getAsString(FacesContext fc, UIComponent uic, Object o) {
//This will return view-friendly output for the dropdown menu
return ((Category) o).getId().toString();
}
}
在您的<$中引用您的新转换器c $ c>< h：selectOneMenu />
<h:selectOneMenu id="category_fk"
converter="#{categoryConverterBean}"
value="#productController.product.category_fk}"
title="Category_fk" >
<!-- DONE: update below reference to list of available items-->
<f:selectItems value="#{productController.categoryList}"
var="prodCat" itemValue="#{prodCat.category_id}"
itemLabel="#{prodCat.name}"/>
</h:selectOneMenu>
我们使用的名称是 categoryConverterBean 因为我们想利用您在转换器中提取的实体管理器技巧。在任何其他情况下，您将使用您在转换器注释上设置的名称。
We're using the name categoryConverterBean because we want to take advantage of the entity manager trick you pulled in the converter. Any other case, you would've used the name you set on the converter annotation.
这篇关于'null Converter'的转换错误设置值'52'的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！