嵌套JSF表达式字符串

Question

我想使用值表达式的动态参数来实现此目的:

<h:dataTable value="#{someBean.someValue}" var="field">
    <h:column>#{anotherBean[field]}</h:column>
</h:dataTable>

这里field是'user.name'或'location.address.zip'或...

可能吗？

请注意,这是一个简单的例子,我对组件ValueExpression不感兴趣dataTable.

现在更新的问题是:如何替换标准的BeanELResolver？

寻找ELUtils:

    ...
    composite.addRootELResolver(IMPLICIT_RESOLVER);
    composite.add(FLASH_RESOLVER);
    composite.addPropertyELResolver(COMPOSITE_COMPONENT_ATTRIBUTES_EL_RESOLVER);
    addELResolvers(composite, associate.getELResolversFromFacesConfig());
    addVariableResolvers(composite, FacesCompositeELResolver.ELResolverChainType.Faces,
            associate);
    addPropertyResolvers(composite, associate);
    composite.add(associate.getApplicationELResolvers());
    composite.addRootELResolver(MANAGED_BEAN_RESOLVER);
    composite.addPropertyELResolver(RESOURCE_RESOLVER);
    composite.addPropertyELResolver(BUNDLE_RESOLVER);
    ...

但我还没有完全理解旋转变压器链......所以我会去学习:)

更新2

这段代码有效;)

public class ExtendedBeanELResolver extends BeanELResolver
{
    @Override
    public Object getValue(ELContext context, Object base, Object property) throws NullPointerException, PropertyNotFoundException, ELException
    {
        try
        {
            return super.getValue(context, base, property);
        }
        catch(PropertyNotFoundException e)
        {
            try
            {
                Object value = base;

                for(String part : property.toString().split("\\."))
                {
                    value = super.getValue(context, value, part);
                }

                return value;
            }
            catch(PropertyNotFoundException e1)
            {
                context.setPropertyResolved(false);
            }
        }

        return null;
    }
}

Answer 1

默认情况下不支持此操作.你需要一个自定义ELResolver.最简单的是扩展现有的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);
        }
    }

}

要使其运行,请按以下方式注册faces-config.xml:

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