使用setPropertyActionListener查看范围限定的受管bean

问题描述

我似乎无法使视图范围的托管bean与setPropertyActionListener一起使用:

I cant seem to get the view scoped managed bean to work with setPropertyActionListener:

   <h:commandButton value="Edit"  action="edit-company.xhtml">
    <f:setPropertyActionListener target="#{companyHolder.item}" value="#{company}"/>
   </h:commandButton>

如果companyHolder为会话或请求范围，则此方法正常，但如果其view为范围，则该方法不起作用.这正常吗?

This works fine if companyHolder is session or request scoped but doesnt work if its view scoped. Is this normal?

推荐答案

创建新视图时，将创建一个全新的视图作用域bean.目标视图与视图作用域bean的实例不同，该实例与通过action方法在具有表单的初始视图上设置属性的位置不同.

A brand new view scoped bean is been created when a new view is created. The target view holds a different instance of the view scoped bean than where the property is been set by the action method on the initial view with the form.

乍一看，这确实不直观，但这就是视图作用域的工作方式.一个视图范围的bean只要它存在就可以生存.毕竟是有道理的.

This is at first sight indeed unintuitive, but that's how the view scope works. A view scoped bean lives as long as the view lives. It makes sense after all.

您最好的选择是使用<f:param>而不是<f:setPropertyActionListener>，并让目标视图通过<f:viewParam>进行设置.

Your best bet is using <f:param> instead of <f:setPropertyActionListener> and let the target view set it by <f:viewParam>.

例如

<h:commandButton value="Edit"  action="edit-company.xhtml">
    <f:param name="companyId" value="#{company.id}"/>
</h:commandButton>

使用

<f:metadata>
    <f:viewParam name="companyId" value="#{bean.company}" required="true" />
</f:metadata>

和

@ManagedBean
@ViewScoped
public class Bean {

    private Company company;

    // ...
}

和

@FacesConverter(forClass=Company.class)
public class CompanyConverter implements Converter {

    @Override
    public void getAsObject(FacesContext context, UIComponent component, Object value) throws ConverterException {
       try {
           return companyService.find(Long.valueOf(value));
       } catch (Exception e) {
           throw new ConverterException(new FacesMessage(
               String.format("Cannot convert %s to Company", value)), e);
       }
    }

    // ...
}

作为另一种完全不同的选择，您还可以通过返回void或null并导航到相同的视图，并有条件地呈现包含内容.

As a completely different alternative, you can also just navigate back to the same view by returning void or null and render the include conditionally.

<ui:include src="#{bean.editmode ? 'edit' : 'view'}.xhtml" />

但是，如果您需要支持GET而不是POST(则需要将<h:commandButton>替换为<h:button>)，则此方法不起作用.

This however doesn't work if you require to support GET instead of POST (for which you would need to replace <h:commandButton> by <h:button> by the way).

这篇关于使用setPropertyActionListener查看范围限定的受管bean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！