Using a script engine (javax.script.ScriptEngine) for implementing a FXML
controller there are two
important information missing in the ScriptContext.ENGINE_SCOPE Bindings
supplied to the script used
to eval() the script code:
* ScriptEngine.FILENAME
o This value denotes the file name from where the script code was fetched
that is being eval()'d.
o When debugging script controllers in a complex JavaFX application it is
mandatory to know
the file name the script code was taken from (as such scripts could be
called/run from
different FXML files). Also, in the case of script runtime errors,
usually the file name is
given by the script engine where the error has occurred to ease
debugging, such that it is
important to really supply the filename.
+ Note: the 'location'-URL in ScriptContext.GLOBAL_SCOPE refers the
FXML file, not to the
file that hosts the script that gets run if using the "<fx:script"
element where the
"source" attribute denotes the name of the script file.
o General solution: supply the appropriate ScriptEngine.FILENAME entry to
the
ScriptContext.ENGINE_SCOPE Bindings.
* ScriptEngine.ARGV
o This value denotes the arguments that get passed to the script from
Java in form of a Java
Array of type Object.
o When defining event handlers in FXML files in script code the script
does not get the
appropriate argument. Rather the script programmer needs to access the
ScriptContext.ENGINE_SCOPE and fetch the entry named "event" from
there. Some script engines
may make the entries in the Bindings implicitly available to the
scripts, however this
cannot be expected by default. However, a ScriptEngine.ARGV entry must
be supplied to the
script by the script engine implementor, such that a script coder gets
the event object
argument in the script language's manner.
o General solution: supply the appropriate ScriptEngine.ARGV Object array
to the
ScriptContext.ENGINE_SCOPE Bindings.
With these two changes not only writing controller scripts would be eased, it
also would
instrumentate ScriptContext.ENGINE_SCOPE Bindings the way it was intended by
JSR-223.
Enclosed please find a tested diff for FXMLLoader.java from the current
OpenJavaFX Master (version
14) that implements both, ScriptEngine.FILENAME entries for all script
invocations and in the case
of a script event handler the appropriate ScriptEngine.ARGV entry gets
supplied, allowing the script
to fetch the event object directly as an argument.
As I have signed the OCA the code (in form of a git diff) can be directly
applied to FXMLLoader.java.
If you need the patch in a different form, then please advise.
---rony
diff --git a/modules/javafx.fxml/src/main/java/javafx/fxml/FXMLLoader.java
b/modules/javafx.fxml/src/main/java/javafx/fxml/FXMLLoader.java
index 7f3d2f3083..eab4541659 100644
--- a/modules/javafx.fxml/src/main/java/javafx/fxml/FXMLLoader.java
+++ b/modules/javafx.fxml/src/main/java/javafx/fxml/FXMLLoader.java
@@ -1558,6 +1558,12 @@ public class FXMLLoader {
location = new URL(FXMLLoader.this.location, source);
}
+ Bindings engineBindings =
engine.getBindings(ScriptContext.ENGINE_SCOPE);
+ Bindings localBindings = engine.createBindings();
+ localBindings.put(engine.FILENAME, location.getPath());
+ localBindings.putAll(engineBindings);
+ scriptEngine.setBindings(localBindings,
ScriptContext.ENGINE_SCOPE);
+
InputStreamReader scriptReader = null;
try {
scriptReader = new
InputStreamReader(location.openStream(), charset);
@@ -1569,6 +1575,9 @@ public class FXMLLoader {
scriptReader.close();
}
}
+
+ // Restore the original bindings
+ engine.setBindings(engineBindings,
ScriptContext.ENGINE_SCOPE);
} catch (IOException exception) {
throw constructLoadException(exception);
}
@@ -1582,7 +1591,16 @@ public class FXMLLoader {
if (value != null && !staticLoad) {
// Evaluate the script
try {
+ Bindings engineBindings =
scriptEngine.getBindings(ScriptContext.ENGINE_SCOPE);
+ Bindings localBindings = scriptEngine.createBindings();
+ localBindings.put(scriptEngine.FILENAME,
location.getPath());
+ localBindings.putAll(engineBindings);
+ scriptEngine.setBindings(localBindings,
ScriptContext.ENGINE_SCOPE);
+
scriptEngine.eval((String)value);
+
+ // Restore the original bindings
+ scriptEngine.setBindings(engineBindings,
ScriptContext.ENGINE_SCOPE);
} catch (ScriptException exception) {
System.err.println(exception.getMessage());
}
@@ -1687,6 +1705,9 @@ public class FXMLLoader {
Bindings engineBindings =
scriptEngine.getBindings(ScriptContext.ENGINE_SCOPE);
Bindings localBindings = scriptEngine.createBindings();
localBindings.put(EVENT_KEY, event);
+ localBindings.put(scriptEngine.ARGV, new Object[]{event});
+ URL location=(URL)
scriptEngine.getBindings(ScriptContext.GLOBAL_SCOPE).get(LOCATION_KEY);
+ localBindings.put(scriptEngine.FILENAME, location.getPath());
localBindings.putAll(engineBindings);
scriptEngine.setBindings(localBindings,
ScriptContext.ENGINE_SCOPE);
