Spring Autowired with Qualifier automatically converting Map to List?

[Peter Kovac]

Hi All,

In an existing code I saw the following:

@Autowired
public void setSystemDefaultFields (@Qualifier("systemFields") List<Map<String, Field>> systemFields)
{
     // .... use systemFields
}

and in XML :

<util:map id="systemFields">
     <entry>
         <key>
             <util:constant static-field="com.my.FIELD_NAME_1"/>
         </key>
         <bean class="com.my.FIELD"> .. properties omitted ... </bean>
     </entry>
</util:map>

My question if systemFields is declared as Map in XML why is it possible to use it as List<Map<String, Field>> parameter in setSystemDefaultFields?

Is it something like that if there are multiple systemFields definitions they're merged into a list?

[Mark Spritzler]

"Is it something like that if there are multiple systemFields definitions they're merged into a list?"

Well, yes and no.

The no part, One you can't make more than one bean be called systemFields in Spring. Basically, that id/name, is used in Spring in a Map as a key, so only one "systemFields" key could ever be in a Map. But that isn't your Map in your code. So only one systemFields bean is merged into a List.

So, the yes part. If you did not have @Qualifier there, then Spring will go out and find all the beans of type Map<String, Field> and automatically put them all into a List and do the autowiring.

Hope that helps

Mark

[Peter Kovac]

Mark Spritzler wrote:
So, the yes part. If you did not have @Qualifier there, then Spring will go out and find all the beans of type Map<String, Field> and automatically put them all into a List and do the autowiring.

Thanks for the answer.

The thing I don't get is why the code uses List<Map<String, Field>> instead of Map<String, Field>? Is that a precaution in case somebody specifies multiple maps of the same key and value types?

I guess if @Qualifier is used then Map<String, Field> would suffice and don't need List?

Thanks,

[Mark Spritzler]

Yeah, can't tell you what they were thinking when they passed in a List of those Maps to their api.

Are they still around that you can ask them?

Mark

[Peter Kovac]

Mark Spritzler wrote:
Are they still around that you can ask them?

Nope, but thanks for the information.