Java 如何获取前缀为“abc”的所有属性。来自 PropertyPlaceholderConfigurer
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How can I get all properties with prefix 'abc.' from PropertyPlaceholderConfigurer
提问by Freewind
In spring context file, I use org.springframework.beans.factory.config.PropertyPlaceholderConfigurerto load several configuration files:
在spring上下文文件中，我org.springframework.beans.factory.config.PropertyPlaceholderConfigurer用来加载几个配置文件：
<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations">
<list>
<value>a.properties</value>
<value>b.properties</value>
<value>c.properties</value>
</list>
</property>
</bean>
The a.properties, b.properties, c.propertesmay have some hibernate configurations which have prefix of abc.:
的a.properties，b.properties，c.propertes可能具有的前缀一些休眠的配置abc.：
abc.hibernate.show_sql=true
abc.hibernate.default_schema=myschema
abc.hibernate.xxx=xxx
abc.hibernate.xxx=xxx
abc.hibernate.xxx=xxx
abc.hibernate.xxx=xxx
abc.hibernate.xxx=xxx
abc.hibernate.xxx=xxx
Now I want to define a hibernate session factory:
现在我想定义一个休眠会话工厂：
<bean id="sessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
<property name="hibernateProperties">
<util:properties>
<prop key="hibernate.show_sql">${abc.hibernate.show_sql}</prop>
<prop key="hibernate.xxx">${abc.hibernate.xxx}</prop>
<prop key="hibernate.xxx">${abc.hibernate.xxx}</prop>
<prop key="hibernate.xxx">${abc.hibernate.xxx}</prop>
<prop key="hibernate.xxx">${abc.hibernate.xxx}</prop>
<prop key="hibernate.xxx">${abc.hibernate.xxx}</prop>
</util:properties>
</property>
</bean>
You can see I have to write the property in bean declaration again and again:
你可以看到我必须一次又一次地在 bean 声明中写入属性：
<prop key="hibernate.xxx">${abc.hibernate.xxx}</prop>
Is there any way to just tell spring to get all properties which have prefix abc.?
有什么方法可以告诉 spring 获取所有具有前缀的属性abc.吗？
So I can write:
所以我可以写：
<bean id="sessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
<property name="hibernateProperties">
<something prefix="abc" /> <!-- TODO -->
</property>
</bean>
Is it possible or is there any other simple solutions for it?
是否有可能或是否有其他简单的解决方案？
回答by Vlad
You can use something like the following class to extend java.util.Properties:
您可以使用类似于以下类的内容来扩展 java.util.Properties：
import java.util.Enumeration;
import java.util.Properties;
public class PrefixedProperties extends Properties {
public PrefixedProperties(Properties props, String prefix){
if(props == null){
return;
}
Enumeration<String> en = (Enumeration<String>) props.propertyNames();
while(en.hasMoreElements()){
String propName = en.nextElement();
String propValue = props.getProperty(propName);
if(propName.startsWith(prefix)){
String key = propName.substring(prefix.length());
setProperty(key, propValue);
}
}
}
}
Then you can define sessionFactory as following:
然后你可以定义 sessionFactory 如下：
<bean id="sessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
<property name="hibernateProperties">
<bean id="sessionFactoryProperties" class="PrefixedProperties">
<constructor-arg ref="props"/> <!-- reference to all properties -->
<constructor-arg value="abc.hibernate."/> <!-- prefix -->
</bean>
</property>
</bean>
I don't see any other possibility to filter properties.
我看不到任何其他过滤属性的可能性。
回答by Sean Patrick Floyd
The PropertyPlaceHolderConfigureris a special construct that is meant for bean creation only. It does not expose the underlying properties in a way that you can access.
这PropertyPlaceHolderConfigurer是一个特殊的构造，仅用于创建 bean。它不会以您可以访问的方式公开底层属性。
A possible workaround is to subclass PropertyPlaceHolderConfigurer, as I have outlined in a previous answer of mine.
一种可能的解决方法是子类化PropertyPlaceHolderConfigurer，正如我在我之前的回答中概述的那样。
Another way is to have a custom PropertiesFactoryBean, like this one:
另一种方法是使用自定义 PropertiesFactoryBean，如下所示：
public class PrefixedPropertyFactoryBean extends AbstractFactoryBean<Properties> {
private List<Resource> locations;
public void setLocations(List<Resource> locations) { this.locations = locations; }
private String prefix;
public void setPrefix(String prefix) { this.prefix = prefix; }
@Override public Class<?> getObjectType() { return Properties.class; }
@Override
protected Properties createInstance() throws Exception {
Properties properties = new Properties();
for (Resource resource : locations) {
properties.load( resource.getInputStream());
}
final Iterator<Object> keyIterator = properties.keySet().iterator();
while(keyIterator.hasNext()) {
if(!keyIterator.next().toString().startsWith(prefix))
keyIterator.remove();
}
return properties;
}
}
You can use this in your XML as follows:
您可以在您的 XML 中使用它，如下所示：
<bean id="hibernateProps" class="some.path.PrefixedPropertyFactoryBean">
<property name="locations">
<list>
<value>a.properties</value>
<value>b.properties</value>
<value>c.properties</value>
</list>
</property>
<property name="prefix" value="abc.hibernate" />
</bean>
<bean id="sessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
<property name="hibernateProperties" ref="hibernateProps" />
</bean>
This is of course redundant, as you'd probably still have to wire the PropertyPlaceHolderConfigurerto set up your other beans.
这当然是多余的，因为您可能仍然需要连接PropertyPlaceHolderConfigurer来设置其他 bean。
回答by Jose Luis Martin
As Sean said, PropertyPlaceHolderConfigurerdon't expose his properties, but you could use reflection to filter them.
正如肖恩所说，PropertyPlaceHolderConfigurer不要暴露他的属性，但你可以使用反射来过滤它们。
public static Properties filterProperties(String prefix, PropertyPlaceholderConfigurer ppc) {
Properties props = new Properties();
Method method = ReflectionUtils.findMethod(PropertiesLoaderSupport.class, "mergeProperties");
ReflectionUtils.makeAccessible(method);
Properties all = (Properties) ReflectionUtils.invokeMethod(method, ppc);
for (String key : all.stringPropertyNames()) {
if (key.startsWith(prefix))
props.setProperty(key, all.getProperty(key));
}
return props;
}
And inject with spel
并用拼写注入
<bean id="ppc" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
...
</bean>
<bean id="sessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
<property name="hibernateProperties" value="#{T(SomeClass).filterProperties('abc.', @ppc)}" />
</bean>
