Default Values for Configuration with @Value

[mrenteln]

I have tried to use the new @Value-Annotation of Spring 3.0 to configure the application.

My config file has some properties like

month=2010-02
#start_date=2009-12-01
#end_date=2009-12-31
...

It is referenced in the Spring configuration with

<util:properties id="props" location="file:application.properties" />

In my central Config class I use the @Value-Annotation to reference these properties:

private @Value("#{props.month}") String month;

private @Value("#{props.end_date}") String sEndDate;

private @Value("#{props.start_date}") String sStartDate;

As you can see above, the property month is set in the configuration file, start_date and end_date are commented out. They are only neccessary if month is not set.

If I set every property (remove the #) everything is fine. If I start the application with the mentioned configuration I get an exception:
EL1008E: (pos 6): Field or property 'end_date' cannot be found on object of type 'java.util.Properties'

OK, Properties return null if a key is not set. But I think this should not produce an Exception... The PropertyPlaceholderConfigurer can be configured to ignore not existing properties. Is there a possibility to define a default value or ignore properties that are not set with @Value?

[mrenteln]

I found out that one can write

private @Value("#{props['end_date']}") String sEndDate;

instead. The bean props is of type java.util.Properties so one can access the properties as attributes using "props.foo" or the "map-way" using "props['foo']". The first one throws an exception if the property is missing because it interprets it as missing attribute. The last one simply ignores it...

[amit.kapps]

With SPEL you can do slightly more complex conditional logic as well.
eg. in your case - use end date if month is not null

[eyal]

A very simple solution is to use the following syntax:

${propertyName:default}