[jira] [Comment Edited] (JEXL-342) Support for Java Optional.

["Garret Wilson (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/JEXL-342?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17270914#comment-17270914 ] 

Garret Wilson edited comment on JEXL-342 at 1/24/21, 4:02 PM:
--------------------------------------------------------------

To get really wil

To get really wild, we could get the Elvis operator working, too. Using the API in the description, I would want to have the following JEXL expression work equivalent to the Java code {{foo.findBar("test").map(Bar::getName).orElse("unavailable")}}:

{code}
foo.bar("test").name ?: "unavailable"
{code}

I realize that under the hood this could get pretty complicated and that the current design of JEXL may not be amenable to this, so I didn't place it in the main feature request description. But it does show the sort of native support that would be nice.

In the least, recognizing the {{findXXX()}} getter pattern and turning {{Optional<>}} to a nullable by calling {{orElse(null)}} during instance tree traversal (and treating as you normally would treat a {{null}} return value to short-circuit expression evaluation) should be completely doable and likely not too much trouble.


was (Author: garretwilson):
To get really wil

To get really wild, we could get the Elvis operator working, too. Using the API in the description, I would want to have the following JEXL expression work equivalent to the Java code {{foo.findBar("test").map(Bar::getName).orElse("no such bar")}}:

{code}
foo.bar("test").name ?: "no such bar"
{code}

I realize that under the hood this could get pretty complicated and that the current design of JEXL may not be amenable to this, so I didn't place it in the main feature request description. But it does show the sort of native support that would be nice.

In the least, recognizing the {{findXXX()}} getter pattern and turning {{Optional<>}} to a nullable by calling {{orElse(null)}} during instance tree traversal (and treating as you normally would treat a {{null}} return value to short-circuit expression evaluation) should be completely doable and likely not too much trouble.

> Support for Java Optional.
> --------------------------
>
>                 Key: JEXL-342
>                 URL: https://issues.apache.org/jira/browse/JEXL-342
>             Project: Commons JEXL
>          Issue Type: New Feature
>    Affects Versions: 3.1
>            Reporter: Garret Wilson
>            Priority: Major
>
> Does JEXL provide any native support for Java 8+ {{Optional<>}}? If not can this this easily be added as some sort of plugin, or better yet can it be added to the library?
> h3. {{Optional}} Traversal
> I need to create an API that works well for application developers as for those using templates with JEXL expressions. Let's say that the {{Bar}} class has a {{Bar.getName()}}. And the {{Foo}} class has this method:
> {code:java}
> Optional<Bar> getBar(String barId);
> {code}
> In code getting the "test" foo-bar name would be like this:
> {code:java}
> String fooBarName=foo.getBar("test").map(Bar::getName).orElse(null);
> {code}
> I want the navigation across {{Optional<>}} to work just as if it were a nullable variable. That is, I want the following JEXL expression to give the same result as {{fooBarName}} above:
> {code}
> foo.bar("test").name
> {code}
> If {{Foo.getBar(String)}} returned a nullable rather than an {{Optional<>}}, I think JEXL would work for this already. but the whole point of {{Optional<>}} is that I keep nullables out of my code, so I don't want to create inferior APIs inconsistent with the rest of my project just to work with JEXL.
> h3. {{Optional}} Getter Name
> As icing on the cake, I would like to have {{Optional<>}} returning getter discovery to recognize the {{findXXX}} pattern, as [Stephen Colebourne suggested|https://blog.joda.org/2015/09/naming-optional-query-methods.html]. I've been using this pattern for several years, and I really like it. Thus to indicate that the {{Foo.getBar(String)}} "getter" doesn't return a nullable but an {{Optional<>}}, I would name it {{Foo.findBar(String)}}, like this:
> {code:java}
> Optional<Bar> getBar(String barId);
> {code}
> I would thus want the exact same JEXL expression above to still work:
> {code}
> foo.bar("test").name
> {code}
> Otherwise I'll have to forego use of modern Java constructs and make an outdated style and less safe API just to get JEXL to work.



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