How to Retrieve Multiple Values from a Spring .properties File as an Array

How can I correctly retrieve multiple values from a Spring .properties file and store them as an array or list?

base.module.elementToSearch=1,2,3,4,5,6

When using Spring to load properties from a .properties file, multiple entries with the same key will not aggregate values into a list automatically. Instead, only the last value is retained. To solve this and effectively retrieve multiple values as a list, you can utilize a combination of property handling and the SpEL (Spring Expression Language).

<bean id="some"
      class="com.some.Class">
      <property name="property" value="#{{'${base.module.elementToSearch}'.split(',')}}" />
</bean

Causes

• Spring's property resolver does not support mapping multiple properties with the same key directly into a collection.
• The last defined property overwrites previous entries when using the same key.

Solutions

• Aggregate the values in a single property entry, like you mentioned (using commas to separate values).
• Alternatively, you can create a custom property editor or use Spring's conversion service for more complex scenarios.

Mistake: Defining multiple properties with the same key in the .properties file and expecting them to aggregate automatically.

Solution: Use a single property with values separated by commas instead.

Mistake: Assuming that just using SpEL will work without correct formatting of the property value in the XML configuration.

Solution: Ensure your property value is formatted correctly to utilize SpEL effectively.