无法访问 p:columns 中托管 bean 中的嵌套属性

问题描述

我有以下两个简单的 POJO:

I have following two simple POJOs:

class Person {
   String name
   Address address;
   //and of course the getter/setter for the attributes
}

class Address {
   String city;
   //also getter/setter for this attribute
}

还有一个支持 bean:

And a backing bean:

@ManagedBean
@RequestScoped
class PersonController {

    private List persons;
    private List<String> columns = Arrays.toList("name", "address.city");
   //of course getter/setter
}

现在我想创建一个数据表.

Now I want to create a dataTable.

<p:dataTable var="person" value="#{personController.persons}" columnIndexVar="index">
    <p:columns var="column" value="#{personController.columns}">
        <h:outputText value="#{person[column]}"/>
    <p:columms>
</p:dataTable>

当我执行这个时，我得到一个 ServletException:

When I execute this I get a ServletException:

Person 类没有属性address.city".

但是如果尝试在 p:columns 中像这样访问属性城市:

But if a try to access the property city like this within p:columns:

<h:outputText value="#{person.address.city}"/>

一切正常.

为什么我不能访问像 #{person['address.city']} 这样的嵌套属性?我如何在 p:columns 中访问它?

Why I can not access a nested property like that #{person['address.city']}? And how can I access it within p:columns?

推荐答案

默认情况下不支持在大括号表示法字符串表达式中嵌套 bean 属性，例如 #{person['address.city']}.你基本上需要一个#{person['address']['city']}.

Nested bean properties in a brace notation string expression like #{person['address.city']} is by default not supported. You basically need a #{person['address']['city']}.

您需要一个自定义的 ELResolver 在这里.最简单的方法是扩展现有的BeanELResolver.

You need a custom ELResolver here. Easiest is to extend the existing BeanELResolver.

这是一个启动示例:

public class ExtendedBeanELResolver extends BeanELResolver {

    @Override
    public Object getValue(ELContext context, Object base, Object property)
        throws NullPointerException, PropertyNotFoundException, ELException
    {
        if (property == null || base == null || base instanceof ResourceBundle || base instanceof Map || base instanceof Collection) {
            return null;
        }

        String propertyString = property.toString();

        if (propertyString.contains(".")) {
            Object value = base;

            for (String propertyPart : propertyString.split("\.")) {
                value = super.getValue(context, value, propertyPart);
            }

            return value;
        }
        else {
            return super.getValue(context, base, property);
        }
    }

}

要让它运行，在faces-config.xml中注册如下:

To get it to run, register it as follows in faces-config.xml:

<application>
    <el-resolver>com.example.ExtendedBeanELResolver</el-resolver>
</application>

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