java 在 spring 配置中使用属性
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/7241356/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Using Properties in spring config
提问by echox
I have a property configuration depending on my environment, like this:
根据我的环境，我有一个属性配置，如下所示：
<bean id="someConfigurer"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations">
<list>
<value>classpath:properties/database.${my.env}.properties</value>
<value>classpath:properties/morestuff.${my.env}.properties</value>
[..]
</list>
</property>
</bean>
Now I can keep different property files in my project, for example database.prod.propertiesor database.qual.properties. This works fine, if I start my application with -Dmy.env=foobar.
现在我可以在我的项目中保留不同的属性文件，例如database.prod.properties或database.qual.properties。这很好用，如果我用 -Dmy.env=foobar 启动我的应用程序。
What happens if no environment is supplied? The application won't start, because of a FileNotFoundException thrown by the PropertyPlaceholderConfigurer. I don't want to keep a copy of all property files as a fallback. What I want is to set a environment as fallback, if the system property is not set.
如果没有提供环境会发生什么？由于 PropertyPlaceholderConfigurer 抛出 FileNotFoundException，应用程序将无法启动。我不想保留所有属性文件的副本作为后备。如果未设置系统属性，我想要的是将环境设置为后备。
I tried to solve this with a second PropertyPlaceholderConfigurer like:
我试图用第二个 PropertyPlaceholderConfigurer 来解决这个问题，比如：
<bean id="fallbackPropertyConfigurer"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations">
<list>
<value>classpath:properties/default-env.properties</value>
</list>
</property>
<property name="order" value="0" />
<property name="ignoreUnresolvablePlaceholders" value="true"/>
<property name="systemPropertiesModeName" value="SYSTEM_PROPERTIES_MODE_OVERRIDE"/>
</bean>
default-env.propertiesconsists of just one property: my.env=qual.
default-env.properties仅包含一个属性：my.env=qual.
The order is set to '0' to be sure, that this bean is evaluated first. I still get the following exception:
order 设置为“0”以确保首先评估此 bean。我仍然收到以下异常：
DEBUG o.s.c.e.PropertySourcesPropertyResolver - Searching for key 'my.env' in [systemProperties]
DEBUG o.s.c.e.PropertySourcesPropertyResolver - Searching for key 'my.env' in [systemEnvironment]
DEBUG o.s.c.e.PropertySourcesPropertyResolver - Could not find key 'my.env' in any property source. Returning [null]
DEBUG o.s.b.f.s.DefaultListableBeanFactory - Finished creating instance of bean 'someConfigurer'
INFO o.s.b.f.c.PropertyPlaceholderConfigurer - Loading properties file from class path resource [properties/default-env.properties]
INFO o.s.b.f.c.PropertyPlaceholderConfigurer - Loading properties file from class path resource [properties/database.${my.env}.properties]
INFO o.s.b.f.s.DefaultListableBeanFactory - Destroying singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@435a3a: defining beans [fallbackPropertyConfigurer,someConfigurer,[..],org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.context.annotation.ConfigurationClassPostProcessor$ImportAwareBeanPostProcessor#0]; root of factory hierarchy
Exception in thread "main" org.springframework.beans.factory.BeanInitializationException: Could not load properties; nested exception is java.io.FileNotFoundException: class path resource [properties/database.${my.env}.properties] cannot be opened because it does not exist
at org.springframework.beans.factory.config.PropertyResourceConfigurer.postProcessBeanFactory(PropertyResourceConfigurer.java:87)
at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:681)
[..]
If I comment out the PropertyPlaceholderConfigurer to get rid of the errors I can use %{my.env}in other beans.
如果我注释掉 PropertyPlaceholderConfigurer 以消除我可以%{my.env}在其他 bean 中使用的错误。
Can anybody explain this behavior?
有人可以解释这种行为吗？
采纳答案by FrVaBe
You can set your default value (in Spring 3) like this:
您可以像这样设置默认值（在 Spring 3 中）：
${my.env:qual}
回答by Adriaan Koster
I suggest to localize your build using the Maven Assembly plugininstead of fiddling with filenames in your Spring context.
我建议使用Maven Assembly 插件本地化您的构建，而不是在 Spring 上下文中摆弄文件名。
回答by ragav k
as farmor said, the property 'ignoreUnresolvablePlaceholders' should be set with true for the 1st bean too, as explained in API..
正如farmor所说，第一个bean的属性“ignoreUnresolvablePlaceholders”也应该设置为true，如API中所述。
Default is "false": An exception will be thrown if a placeholder fails to resolve. Switch this flag to "true" in order to preserve the placeholder String as-is in such a case, leaving it up to other placeholder configurers to resolve it.
默认为“false”：如果占位符无法解析，则会抛出异常。将此标志切换为“true”，以便在这种情况下按原样保留占位符字符串，将其留给其他占位符配置器来解决。
回答by Fareed Alnamrouti
you can also use:
您还可以使用：
<property name="ignoreResourceNotFound" value="true"/>
<property name="ignoreUnresolvablePlaceholders" value="true"/>
回答by Farmor
A longshoot try to add
一个长镜头尝试添加
property name="ignoreUnresolvablePlaceholders" value="true"/>
属性名称="ignoreUnresolvablePlaceholders" value="true"/>
to your first bean as well
还有你的第一个豆子
