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Spring 3 and Application Settings

Discover how AppDynamics steps in to upgrade your performance game and prevent your enterprise from these top 10 Java performance problems, brought to you in partnership with AppDynamics.

If you use Spring in your applications, you may need to pass some application settings to a spring bean. Your settings can be defined in properties files, in system properties or inside an internal storage.

Let's say we want to use a property inside a spring bean like the following:

<bean id="myBean" class="com.mypackage.MyClass">
        <property name="myProperty">
            <value>${propertyValue}</value>
        </property>
</bean> 

 If propertyValue is defined inside a properties file we should define a propertyConfigurer bean:

<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="location">
            <value>classpath:myfile.properties</value>
        </property>
</bean>

 If we want propertyValue to be overridden by system properties we can specify  systemPropertiesModeName :

<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="location">
            <value>classpath:myfile.properties</value>
        </property>
        <property name="systemPropertiesModeName">
            <value>SYSTEM_PROPERTIES_MODE_OVERRIDE</value>
        </property>
</bean>

If our settings are defined inside a storage system (database, content repository), spring 3 will help us a lot with its new expression language SpEL. This allows for calling methods from a defined spring bean.

Lets say we have a settings bean like the following, where storageService  can be any storage you need:

<bean id="settings" class="com.mypackage.SettingsBean">
        <property name="storageService" ref="storageService"></property>
</bean>

 SettingBean will offer us the propertyValue we need :

public class SettingsBean {
    
    private StorageService storageService;    
    
    public Settings getSettings() {
        return storageService.getSettings();
    }    

    @Required
    public void setStorageService(StorageService storageService) {
        this.storageService = storageService;        
    }
    
    // helper methods used in Spring with SpEL    
    public String getPropertyValue() {
        Settings settings = getSettings();
        return settings.getPropertyValue();
    }
}

 With SpEL we can use the propertyValue in our bean like this:

<bean id="myBean" class="com.mypackage.MyClass">
        <property name="myProperty" value="#{settings.getPropertyValue()}"/>
</bean>

If the bean, which needs some settings from a storage, is a bean from the spring api, then it's very easy to set the properties using SpEL . Otherwise we would have had to extend that class to inject our storage. For example a Spring ThreadPoolTaskExecutor can be defined like this :

<bean id="schedulingTaskExecutor" class="org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor">
        <property name="threadNamePrefix" value="Scheduler-"/>
        <property name="corePoolSize" value="#{settings.getSchedulerCorePoolSize()}"/>
        <property name="maxPoolSize" value="#{settings.getSchedulerMaxPoolSize()}"/>
        <property name="queueCapacity" value="#{settings.getSchedulerQueueCapacity()}"/>
</bean>

 

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