如何在Spring XML上下文中实现条件资源导入？ [英] How to achieve conditional resource import in a Spring XML context?

问题描述

我想要实现的是动态（即基于配置文件中定义的属性）启用/禁用导入子Spring XML上下文的能力。

What I would like to achieve is the ability to "dynamically" (i.e. based on a property defined in a configuration file) enable/disable the importing of a child Spring XML context.

我想象的是：

<import condition="some.property.name" resource="some-context.xml"/>

属性被解析（到布尔值），当为真时，导入上下文，否则它不是't。

Where the property is resolved (to a boolean) and when true the context is imported, otherwise it isn't.

到目前为止我的一些研究：

Some of my research so far:

• 编写自定义NamespaceHandler（及相关类），以便我可以在自己的命名空间中注册自己的自定义元素。例如：< myns：import condition =some.property.nameresource =some-context.xml/>

这种方法的问题在于我不想从Spring复制整个资源导入逻辑，对我来说，我需要委派什么来做这件事并不明显。

The problem with this approach is that I do not want to replicate the entire resource importing logic from Spring and it isn't obvious to me what I need to delegate to to do this.

推荐答案

现在这完全是可能，使用Spring 4.

This is now completely possible, using Spring 4.

在主应用程序内容文件中

In your main application content file

<bean class="com.example.MyConditionalConfiguration"/>

MyConditionalConfiguration看起来像

And the MyConditionalConfiguration looks like

@Configuration
@Conditional(MyConditionalConfiguration.Condition.class)
@ImportResource("/com/example/context-fragment.xml")
public class MyConditionalConfiguration {
    static class Condition implements ConfigurationCondition {
         @Override
         public ConfigurationPhase getConfigurationPhase() {
             return ConfigurationPhase.PARSE_CONFIGURATION;
         }
         @Override
         public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
             // only load context-fragment.xml if the system property is defined
             return System.getProperty("com.example.context-fragment") != null;
         }
    }
}

最后，你把您想要包含在/com/example/context-fragment.xml中的bean定义

And then finally, you put the bean definitions you want included in the /com/example/context-fragment.xml

请参阅 JavaDoc for @Conditional

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