Byron,
Thanks for writing this up. It helps a lot, but I'd like to
clarify the best practice for handling defaults. Is it this:
If you are implementing a crud command then make sure to
specify the default value on both the setter and the getter:
@Attribute(defaultValue="bar" String getFoo();
@Param(defaultValue="bar") void setFoo(String foo);
If you are not implementing a crud command then specify
the default value on the getter only:
@Attribute(defaultValue="bar" String getFoo();
void setFoo(String foo);
Joe
On 01/25/11 06:50 PM, Byron Nevins wrote:
> Jerome explained how the annotations work in configbeans:
>
>
> If you have a default value for the @Param, that will be used to initialise the
> corresponding field in the decorator which will also be used to inject into config
> attribute. However since you do not have a default value of the @Attribute declaration,
> that means the attribute does not have a default value so the command parameter default
> value will always be stored.
>
> think of it another way, if you were not using the CRUD commands (which are the only ones
> looking at the @Param declaration) but create your configuration with a normal config
> transaction (ConfigSupport.apply methods for instance), your resulting xml will not have
> any value unless you do and an explicit setXXX().
>
> for instance :
>
> @Attribute(defaultValue="bar") String getFoo();
> @Param void setFoo(String foo);
>
> no matter how your create your config (transaction, crud), if don't call setFoo(),
> getFoo() will return "bar"
>
> @Attribute String getFoo();
> @Param(defaultValue="bar") void setFoo(String foo);
>
> if you use a transaction to create the config and don't call setFoo() then getFoo() will
> be null.
> if you use CRUD, to create the config, user did not specify the foo option, getFoo() will
> return "bar".
>
> last example :
>
> @Attribute(defaultValue="ba" String getFoo();
> @Param(defaultValue="bar") void setFoo(String foo);
>
> if u create your config with a transaction and don't call setFoo(), getFoo() return "ba"
> if u create your config with a CRUD and foo is not specified by the user, getFoo() return
> "bar"
>
> nobody returns "babar" ;-)
>
> The @Param default value sets an initial value to the field that will be used when
> creating the underlying config.
> The @Attribute default value is the value of the field when not set.
>
> In my last example, I cannot imagine why you would want to have different @Param and
> @Attribute default values set on the @Configured configuration but it's possible maybe for
> compatibility with previous releases, etc
>
>