Hi Rémi,
On 13.01.2015 09:18, Remi Forax wrote:
> does javax.script discovery implementation use java.util.ServiceLoader
> convention ?
The discovery mechanism relies on (cf.
<http://docs.oracle.com/javase/8/docs/api/javax/script/package-summary.html#package.description>):
5. *Script engine discovery and Metadata*: Applications written to the
Scripting API might have
specific requirements on script engines. Some may require a specific
scripting language and/or
version while others may require a specific implementation engine and/or
version. Script engines
are packaged in a specified way so that engines can be discovered at
runtime and queried for
attributes. The Engine discovery mechanism is based on the Service
discovery mechanism described
in the *Jar File Specification*. Script engine implementing classes are
packaged in jar files
that include a text resource named
*META-INF/services/javax.script.ScriptEngineFactory*. This
resource must include a line for each |ScriptEngineFactory|
<http://docs.oracle.com/javase/8/docs/api/javax/script/ScriptEngineFactory.html>
that is
packaged in the jar file. |ScriptEngineManager|
<http://docs.oracle.com/javase/8/docs/api/javax/script/ScriptEngineManager.html>
includes
|getEngineFactories|
<http://docs.oracle.com/javase/8/docs/api/javax/script/ScriptEngineManager.html#getEngineFactories-->
method to get all |ScriptEngineFactory|
<http://docs.oracle.com/javase/8/docs/api/javax/script/ScriptEngineFactory.html>
instances
discovered using this mechanism. |ScriptEngineFactory| has methods to query
attributes about
script engine.
Not sure whether this matches the java.util.ServiceLoader convention.
> If the answer is yes, then it will work out of the box.
If the answer would be yes, how would one make access to such a scripting
engine jar available (e.g.
to Java code running from the Oracle Java plugin in a browser), what needs to
be configured where?
TIA,
---rony
>
> On 01/12/2015 05:09 PM, Rony G. Flatscher wrote:
>> Hi there,
>>
>> reading <http://openjdk.java.net/jeps/220 this is a question or maybe a
>> request for information
>> regarding the removal of the "extension" mechanism and what can be used
>> instead?
>>
>> There is one particular use-case that I regard to be of tremendeous
>> importance for the Java world,
>> recognizing that many Java movers and shakers do not really realize ;) :
>> making javax.script
>> scripting languages available to Java applications.
>>
>> Background: I served as an expert on JSR-223 which defined javax.script
>> (personal background: Apache
>> Commons BSF scripting framework, BSF4ooRexx a JNI-bridge to the opensource
>> ooRexx.org scripting
>> language, which itself is implemented in C++, creator of the Apache
>> OpenOffice AOO ooRexx plugin
>> using the AOO Java scripting framework, teaching at a Business University
>> among other things
>> scripting, ...).
>>
>> "javax.script" defines a discovery mechanism which allows a Java app to
>> enumerate all available
>> scripting engines. This way all discoverable (= installed) javax.script
>> engines are available to any
>> Java app and script/macro programmers. As a result the (end) users become
>> able to pick the script
>> language they wish to use to create macros/scripts for their Java
>> application. [An example would be
>> Apache OpenOffice (AOO), which allows using any script language, provided it
>> is made available via
>> AOOs Java based scripting framework, like BeanShell, JavaScript, ooRexx,
>> et.al.]
>>
>> Please note, that a Java application developer may not even (and need not)
>> know in advance which
>> javax.script engines will be available on a target installation, just that
>> it is rather easy to
>> enumerate the javax.script engines available to it and allow the (end) user
>> programmer to pick one
>> for creating scripts targeted at the Java application.
>>
>> ---
>>
>> Currently (in pre-Java 9 environments), if one wishes to use javax.script
>> engines (e.g. in web
>> browsers via the Oracle browser Java plugin and in parallel in other Java
>> apps), one can make any
>> javax.script engine available by placing it in the Java "extension"
>> directory, which works even
>> then, when Java apps (like the Oracle browser Java plugin or AOO) does not
>> honor the CLASSPATH
>> environment variable.
>>
>> Now, having learned that JDK 9 will remove the "extension" mechanism, I am
>> very interested in
>> learning what alternatives are discussed, planned for Java 9 to enable this
>> particular important
>> use-case: making javax.script engines (packaged as jars) available to any
>> Java app!
>>
>> TIA,
>>
>> ---rony
