PropertyPlaceholderConfigurer，用于读取属性文件和数据库

Question

I am trying to create two PropertyPlaceholderConfigurer's, one for accessing property files and the other for accessing the database... the code is as follows

  <bean id="otherPropertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="ignoreUnresolvablePlaceholders" value="true"/>
        <property name="properties">
        <bean class="org.apache.commons.configuration.ConfigurationConverter" factory-method="getProperties">
            <constructor-arg>
                <bean class="org.apache.commons.configuration.DatabaseConfiguration">
                    <constructor-arg ref="myDataSource"/>
                     <constructor-arg value="dbo.APPLICATIONPROPERTIES"/>
                     <constructor-arg value="NAME"/>
                   <constructor-arg value="VALUE"/>
                </bean>
            </constructor-arg>
        </bean>
        </property>
    </bean>

  <bean id="propertyConfigurer" class="com.fexco.wuams.util.PropertyPlaceholderConfigurer">
        <property name="locations">
            <list>
                <value>classpath:database.properties</value>
            </list>         
        </property>
    </bean>

I have the following ComboPooledDataSource bean

<bean id="myDataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close">
    <property name="driverClass" value="${driver}"/>
    <property name="jdbcUrl" value="${url}"/>
    <property name="user" value="${username}"/>
    <property name="password" value="${password}"/>
    <property name="initialPoolSize" value="5"/>
    <property name="minPoolSize" value="5"/>
    <property name="maxPoolSize" value="5"/>
    <property name="maxIdleTime" value="1200"/>
    <property name="idleConnectionTestPeriod" value="300"/>
  </bean>

which works perfectly for the rest of my application except when i try use it for my bean id="otherPropertyConfigurer" ... i get the following error

Caused by: org.springframework.beans.PropertyBatchUpdateException; nested PropertyAccessExceptions (1) are:
PropertyAccessException 1: org.springframework.beans.MethodInvocationException: Property 'driverClass' threw exception; nested exception is java.beans.PropertyVetoException: Could not locate driver class with name '${jdbc.driverClassName}'.
    at org.springframework.beans.AbstractPropertyAccessor.setPropertyValues(AbstractPropertyAccessor.java:104)
    at org.springframework.beans.AbstractPropertyAccessor.setPropertyValues(AbstractPropertyAccessor.java:59)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1275)
    ... 72 more

if i hardcode the database variables in ComboPooledDataSource (eg change ${jdbc.driverClassName} to net.sourceforge.jtds.jdbc.Driver everything works fine but for some reason when i add the otherPropertyConfigurer , my original propertyConfigurer does not work

Does anyone have any ideas on how to resolve this?

Answer 1

I hate to be the barer of bad news, but what you are trying to achieve, Spring physically can not do.

Because Springs PropertyPlaceholderConfigurer classes as beanPostProcessors, it creates and invokes these beans before the creation of any other beans. However, if you have multiple PropertyPlaceholderConfigurer's, where one depends on another, Spring will always create both instances fully before invoking either of them. Therefore your placeholders in myDataSource can never be resolved.

The problem is better described in this question .

The best solution to this problem is generally to stop using a database for your configuration management. I find that it is better to use a simple configuration file, which can be modified per environment, and hosted in your deployment container.

Answer 2

As ConMan suggested this cannot be done in the way that i was explaining in my question above. But i have managed to resolve this issue my instead passing the properties ( propertiesFromDB ) into the class using the following code

<bean id="propertiesFromDB"
        class="org.springframework.beans.factory.config.PropertiesFactoryBean">
        <property name="properties" ref="configurationFactoryBean" />
    </bean>

    <bean name="configurationFactoryBean"
        class="org.springmodules.commons.configuration.CommonsConfigurationFactoryBean">
        <property name="configurations" ref="applicationProperties" />
    </bean>


    <bean id="applicationProperties" class="org.apache.commons.configuration.DatabaseConfiguration">
        <constructor-arg type="javax.sql.DataSource" ref="myDataSource" />
        <constructor-arg index="1" value="dbo.APPLICATIONPROPERTIES" />
        <constructor-arg index="2" value="NAME" />
        <constructor-arg index="3" value="VALUE" />
    </bean>

i can then get the what ever property i want using the getProperty() method and passing the NAME variable