A Kotlin DSL would be pretty awesome. We’d first need a good way to generate all the relevant type metadata to do code generation. Or it might work better for a scripted DSL since you’d be using actual types of things.
On Tue, May 7, 2019 at 09:11, Raman Gupta <[email protected]> wrote: > A follow-on feature could be a Kotlin DSL. Kotlin is fully typed, but > with a lot of Groovy-like features that enable elegant DSLs. The > Gradle team, for example, has created a Kotlin DSL that can be used > instead of their Groovy DSL. I don't know the details of how it works, > but IntelliJ is able to provide type-safe validation and code > completion for the Gradle Kotlin DSL. I suspect a Kotlin DSL for Log4j > could benefit from the same capabilities. > > Regards, > Raman > > On Fri, May 3, 2019 at 1:08 PM Matt Sicker <[email protected]> wrote: > > > > I believe Ralph has brought up a feature request in the past, though I > > don't remember where. Anyways, Logback has a Groovy DSL [1] as an > > option to configure itself, and we could introduce a similar feature > > built on top of the existing ConfigurationBuilder code from the Java > > DSL in log4j-core. After seeing how easily Groovy integrates with Java > > to form DSLs in Jenkins [2] (more so in the web framework than in > > pipelines, but both are valid), I've been considering working on such > > a feature. > > > > Let's take a random configuration sample from the manual [3]: > > > > <?xml version="1.0" encoding="UTF-8"?> > > <Configuration status="WARN"> > > <Appenders> > > <Console name="Console" target="SYSTEM_OUT"> > > <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level > > %logger{36} - %msg%n"/> > > </Console> > > </Appenders> > > <Loggers> > > <Logger name="com.foo.Bar" level="trace"> > > <AppenderRef ref="Console"/> > > </Logger> > > <Root level="error"> > > <AppenderRef ref="Console"/> > > </Root> > > </Loggers> > > </Configuration> > > > > If I were to translate this to the equivalent Groovy DSL, here is one > > example of how that might look: > > > > configuration(status: 'warn') { > > appenders { > > console(name: 'Console', target: 'SYSTEM_OUT') { > > patternLayout(pattern: '%d{HH:mm:ss.SSS} [%t] %-5level > > %logger{36} - %msg%n') > > } > > } > > loggers { > > logger(name: 'com.foo.Bar', level: 'trace') { > > appenderRef(ref: 'Console') > > } > > root(level: 'error') { > > appenderRef(ref: 'Console') > > } > > } > > } > > > > An alternative syntax would be to switch from using method parameters > > to properties of the closure. For example, that might look like: > > > > configuration { > > status = 'warn' > > console { > > name = 'Console' > > target = 'SYSTEM_OUT' > > patternLayout { > > pattern = '%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n' > > } > > } > > // ... > > } > > > > Are there any preferences on syntax? I don't think we can get super > > fancy with the DSL due to the underlying APIs (i.e., we can't provide > > much in the way of code completion AFAIK), but supporting a dynamic > > DSL like that is fairly easy with Groovy. This does open a question of > > configuration being scripted versus declarative since we'd be offering > > a full script engine technically in order to write your configuration. > > I do not expect this feature to offer a programmatic way of > > manipulating the underlying plugin objects (i.e., this would be for > > building a Configuration, not manipulating a running one); that might > > make more sense with a more standardized plugin API which is a > > wishlist item I have for 3.0. > > > > [1]: https://logback.qos.ch/manual/groovy.html > > [2]: > https://github.com/stapler/stapler/blob/master/groovy/src/main/java/org/kohsuke/stapler/jelly/groovy/JellyBuilder.java > > [3]: https://logging.apache.org/log4j/2.x/manual/configuration.html > > > > -- > > Matt Sicker <[email protected]> > -- Matt Sicker <[email protected]>
