Spring 占位符不适用于自定义架构元素

我试图从占位符中获取一些值到自定义模式属性（cfg:merge elements'target）中，但它不起作用：

somexml.xml:

<bean id="stateMachineNamingStrategy" class="com.mycompany.statemachine.hibernate.StateMachineNamingStrategy">
    <property name="prefix" value="${statemachine.table_prefix}"/>
</bean>

<cfg:merge-elements id="packages-com.mycompany.statemachine" target="${session-factory-pkgs}">
    <value>com.mycompany.statemachine.machine.impl</value>
</cfg:merge-elements>

---

为什么它不将占位符转换为它的值？？？

以防有人遇到同样的问题：

事实证明，在我的

NamespaceHandler

中，我注册了一个新的BeanDefinition，它扩展了

BeanDefinitionRegistryPostProcessor

。这些特殊的后处理器在正常的

BeanFactoryPostProcessor

之前执行，以允许注册或删除BeanDefinitions。因此，无法在BeanDefinitionRegistryPostProcessor之前执行PropertyPlaceHolderConfigure（这是一个普通的BeanPostProcessor）

您可以在XmlWebApplicationContext（AbstractApplicationContext）中看到这一切。invokeBeanFactoryPostProcessors：

        Map<String, BeanDefinitionRegistryPostProcessor> beanMap =
                beanFactory.getBeansOfType(BeanDefinitionRegistryPostProcessor.class, true, false);
        List<BeanDefinitionRegistryPostProcessor> registryPostProcessorBeans =
                new ArrayList<BeanDefinitionRegistryPostProcessor>(beanMap.values());
        OrderComparator.sort(registryPostProcessorBeans);
        for (BeanDefinitionRegistryPostProcessor postProcessor : registryPostProcessorBeans) {

            //!!!!! BeanDefinitionRegistryPostProcessors are excecuted!!!!!
            postProcessor.postProcessBeanDefinitionRegistry(registry);
        }
        invokeBeanFactoryPostProcessors(registryPostProcessors, beanFactory);
        invokeBeanFactoryPostProcessors(registryPostProcessorBeans, beanFactory);
        invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
        processedBeans.addAll(beanMap.keySet());
    }
    else {
        // Invoke factory processors registered with the context instance.
        invokeBeanFactoryPostProcessors(getBeanFactoryPostProcessors(), beanFactory);
    }

    // Do not initialize FactoryBeans here: We need to leave all regular beans
    // uninitialized to let the bean factory post-processors apply to them!
    String[] postProcessorNames =
            beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

    // Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
    // Ordered, and the rest.
    List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
    List<String> orderedPostProcessorNames = new ArrayList<String>();
    List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
    for (String ppName : postProcessorNames) {

Map beanMap=
getBeansOfType（BeanDefinitionRegistryPostProcessor.class，true，false）；
列出registryPostProcessorBeans=
新的ArrayList（beanMap.values（））；
排序（registryPostProcessorBeans）；
for（BeanDefinitionRegistryPostProcessor后处理器：registryPostProcessorBeans）{
//！！！！！BeanDefinitionRegistryPostProcessor已超出限制！！！！！
postProcessor.postProcessBeanDefinitionRegistry（注册表）；
}
invokeBeanFactoryPostProcessors（registryPostProcessors，beanFactory）；
invokeBeanFactoryPostProcessors（registryPostProcessorBeans，beanFactory）；
invokeBeanFactoryPostProcessors（regularPostProcessors，beanFactory）；
processedBeans.addAll（beanMap.keySet（））；
}
否则{
//调用在上下文实例中注册的工厂处理器。
调用BeanFactoryPostProcessors（getBeanFactoryPostProcessors（），beanFactory）；
}
//不要在这里初始化FactoryBeans：我们需要保留所有常规Bean
//未初始化以使bean工厂后处理器应用于它们！
字符串[]后处理程序名称=
getBeanNamesForType（BeanFactoryPostProcessor.class，true，false）；
//在实现PriorityOrdered的BeanFactory后处理器之间进行分离，
//命令，其余的。
List priorityOrderedPostProcessors=new ArrayList（）；
List orderedPostProcessorNames=new ArrayList（）；
List nonOrderedPostProcessorNames=new ArrayList（）；
for（字符串ppName:postProcessorNames）{

        Map<String, BeanDefinitionRegistryPostProcessor> beanMap =
                beanFactory.getBeansOfType(BeanDefinitionRegistryPostProcessor.class, true, false);
        List<BeanDefinitionRegistryPostProcessor> registryPostProcessorBeans =
                new ArrayList<BeanDefinitionRegistryPostProcessor>(beanMap.values());
        OrderComparator.sort(registryPostProcessorBeans);
        for (BeanDefinitionRegistryPostProcessor postProcessor : registryPostProcessorBeans) {

            //!!!!! BeanDefinitionRegistryPostProcessors are excecuted!!!!!
            postProcessor.postProcessBeanDefinitionRegistry(registry);
        }
        invokeBeanFactoryPostProcessors(registryPostProcessors, beanFactory);
        invokeBeanFactoryPostProcessors(registryPostProcessorBeans, beanFactory);
        invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
        processedBeans.addAll(beanMap.keySet());
    }
    else {
        // Invoke factory processors registered with the context instance.
        invokeBeanFactoryPostProcessors(getBeanFactoryPostProcessors(), beanFactory);
    }

    // Do not initialize FactoryBeans here: We need to leave all regular beans
    // uninitialized to let the bean factory post-processors apply to them!
    String[] postProcessorNames =
            beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

    // Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
    // Ordered, and the rest.
    List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
    List<String> orderedPostProcessorNames = new ArrayList<String>();
    List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
    for (String ppName : postProcessorNames) {