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Setting dynamic speed properties for maven archetype projects

I am creating an archetype and want to create an accessible project property that contains things like the current date and all the lower case of the artifact identifier. I found an https://stackoverflow.com/a/3126169/ which shows how this should usually be possible.

I tried adding this to the archetype-metadata.xml file like this:

... <requiredProperty key="artifactIdLower"> <defaultValue>${artifactId.toLowerCase()}</defaultValue> </requiredProperty> <requiredProperty key="ldt"> <defaultValue>${package.getClass().forName("java.time.LocalDateTime").getMethod("now").invoke(null)}</defaultValue> </requiredProperty> <requiredProperty key="dtf"> <defaultValue>${package.getClass().forName("java.time.format.DateTimeFormatter").getMethod("ofPattern", $package.getClass().forName("java.lang.String")).invoke(null, "dd MMM yyyy")}</defaultValue> </requiredProperty> <requiredProperty key="date"> <defaultValue>${ldt.format($dtf)}</defaultValue> </requiredProperty> ...

The artifactIdLower property works like a charm, but ldt , dtf and date do not seem to work, which gives an error:

 Null reference [template 'dtf', line 1, column 1] : ${package.getClass().forName("java.time.format.DateTimeFormatter").getMethod("ofPattern", $package.getClass().forName("java.lang.String")).invoke(null, "dd MMM yyyy")} cannot be resolved.

After that, I tried to see where in the chain this null link is. I managed to install pkgClass on $package.getClass() (or on $package.Class ),

but after that I was not able to set $strClass to $package.getClass().forName("java.lang.String") or $pkgClass.forName("java.lang.String") (funnily enough, both pkgClass and strClass must be class objects).

This made me wonder if there is a restriction on the use of reflection within the archetype-metadata.xml.

My question is: how can I set dynamically generated property values ​​(e.g. above) that can be used in a project?

I do not want to define these properties in every file that I create, because there may be more properties that I want to add later.

Edit : Instead, I tried to create a generalproperties.vm file containing the #set directives. This file will then be loaded by each file on the first line using #parse ("generalproperties.vm"). While I received a file that would be parsed from the pom.xml file, it did not behave the way I wanted.

Next entry

 test $null #set( $ldtClass = $package.getClass().forName("java.time.LocalDateTime") ) $ldtClass.Name $ldtClass.getMethod("now") #set( $ldtNowMethod = $ldtClass.getMethod("now") ) $ldtNowMethod.Name #set( $clsLoader = $package.getClass().getClassLoader() ) $clsLoader #set( $ldtClass2 = $clsLoader.loadClass("java.time.LocalDateTime") ) $ldtClass2.Name $ldtClass2.getMethod("now") #set( $ldtNowMethod2 = $ldtClass2.getMethod("now") ) $ldtNowMethod2.Name #set( $ldt = $ldtNowMethod2.invoke($null) ) $ldt #set( $dtf = $package.getClass().forName("java.time.format.DateTimeFormatter").getMethod("ofPattern", $package.getClass().forName("java.lang.String")).invoke($null, "yyyy/MM/dd HH:mm:ss") ) $dtf

Created the following output:

 test $null java.time.LocalDateTime $ldtClass.getMethod("now") $ldtNowMethod.Name $clsLoader $ldtClass2.Name $ldtClass2.getMethod("now") $ldtNowMethod2.Name $ldt $dtf

The first 3 exits are expected, but after that I do not get the results that I want. If someone can solve any of the above problems (with a metadata file or with a generalproperties file), he will be highly appreciated.

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2 answers

This should work:

 ... <requiredProperty key="date"> <defaultValue>${package.getClass().forName("java.time.LocalDateTime").getMethod("now").invoke(null).format($package.Class.forName("java.time.format.DateTimeFormatter").getMethod("ofPattern", $package.Class).invoke(null, "dd MMM yyyy"))}</defaultValue> </requiredProperty> ...
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The only limitation I could think of was to use the SecureUberspector instead of the standard Uberspector in the Velocity configuration settings. But you cannot get the java.time.LocalDateTime class, so that is not the case if, perhaps, if you are using the old version of Velocity. With Velocity 1.7, I can get a reference to the now() method and call it.

Are you also sure that the direct version of Java is working correctly? For example, I read in Class.getClassLoader() that "some implementations may use null to represent the boot class loader. This method returns null in such implementations if this class was loaded by the boot class loader."

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