如何使用 JSF2 处理多态性? [英] How to handle polymorphism with JSF2?

问题描述

我需要显示/编辑多态实体.

I need to display/edit polymorphic entities.

我的抽象类是Person.我的具体课程是 PhysicalPerson 和 MoralPerson

My abstract class is Person. My concrete classes are PhysicalPerson and MoralPerson

每个具体类都有自己的自定义属性.

Each concrete class has its own custom attributes.

如何根据实体类使用合适的显示/编辑(复合)组件?

How can I use the appropriate display/edit (composite) component according to entity class ?

谢谢！:)

推荐答案

EL中没有instanceof这样的东西.但是，您可以(ab)使用 Object#getClass() 并访问 Class 在 EL 中也是如此.然后只需在组件的 rendered 属性中确定结果即可.

There is no such thing as instanceof in EL. You can however (ab)use Object#getClass() and access the getters of Class in EL as well. Then just determine the outcome in the component's rendered attribute.

<h:panelGroup rendered="#{entity.class.name == 'com.example.PhysicalPerson'}">
    <p>According to Class#getName(), this is a PhysicalPerson.</p>
</h:panelGroup>
<h:panelGroup rendered="#{entity.class.simpleName == 'MoralPerson'}">
    <p>According to Class#getSimpleName(), this is a MoralPerson.</p>
</h:panelGroup>

但是，自定义 EL 函数会更干净.请注意，由于 EL 中允许的属性名的严格限制，上述内容不适用于 Tomcat 7 和克隆.不再允许使用诸如 class 之类的 Java 保留字面量.你需要 #{entity['class'].name} 等等.

A custom EL function would be more clean however. Note that the above doesn't work on Tomcat 7 and clones due to extremely restrictive restrictions of allowed propertynames in EL. Java reserved literals such as class are not allowed anymore. You'd need #{entity['class'].name} and so on instead.

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