Spring: PropertyPlaceHolderConfigurer to set values for non-string/integer properties

Question

Hi,

All the examples I have seen where the PropertyPlaceHolderConfigurer is used seem to be setting simple values like Strings and ints.

How do you use the PPC to set the values of classes.

E.g. If i had a class signature Source(String name, DistributionSample batch, DistributionSample delay)

How would I go about setting the batch and delay properties.

There is also a small catch. DistributionSample is an abstract class. On the bright side, The class that is using the propertyPlaceHolder knows the beanName of the "Solid" class that needs to be instantiated.

Any help would be much appreciated.

Answer 1

As you said, PropertyPlaceHolderConfigurer only works for String values which String can convert into the target type.

So you can either tell Spring how to convert a String into DistributionSample objects, or you can use the property placeholders to refer to bean names,e.g.

<bean class="Source">
   <constructor-arg value="source name"/>
   <constructor-arg ref="${batch.beanName}"/>
   <constructor-arg ref="${delay.beanName}"/>
</bean>

<bean id="batch" class="....."/>
<bean id="delay" class="....."/>

If your properties file contains

batch.beanName = batch
delay.beanName = delay

Then the bean references will be resolved. You can also use property placeholder syntax for bean classes, if that's useful for you:

<bean id="sample" class="${batch.classname}/>

Answer 2

Have a look at the PropertyOverrideConfigurer when you want to override properties of specific beans whose assembling you have no control of.

Answer 3

In the end it made more sense to use Castor to map the XML to the java objects.

Castor integrates with spring, so the beans can be instantiated from the Castor marshallers.

Thanks for all the hints and tips guys.