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