JavaFX and Java Technology - JavaFX: Developing Rich Internet Applications - page 298

show them if a ScriptException is encountered. The javax.tools.Diagnostic-
Collector class provides a means to do this.
First, create an instance of DiagnosticCollector , then pass this to either the
compile() or eval() methods on the JavaFXScriptEngine instance.

DiagnosticCollector diags =
new DiagnosticCollector();

try {
CompiledScript compiled =
engine.compile(script, diags );

...

Now, when a ScriptException is thrown, detailed error messages are contained
in the DiagnosticCollector object. Listing 11.5 shows how to list all the error
messages.

Listing 11.5 Java Code - Java Scripting API Error Handling

} catch (ScriptException ex) {
List<Diagnostic> errorList =
diags.getDiagnostics();
Iterator<Diagnostic> iter =
errorList.iterator();
while (iter.hasNext()) {
Diagnostic d = iter.next();
System.out.println(
d.getKind().toString() + ": Line:" +
d.getLineNumber() + " Col:" +
d.getColumnNumber() + "\n'" +
d.getMessage(null) + "'");
}
}

To illustrate this, if we take the Student script and change the getName() function
to return the erroneous instance variable nameBogus . Without diagnostic han-
dling, we get the following fairly useless error message from ScriptException .

javax.script.ScriptException: compilation failed
at com.sun.tools.javafx.script.JavaFXScriptEngineImpl.
parse(JavaFXScriptEngineImpl.java:260)
at com.sun.tools.javafx.script.JavaFXScriptEngineImpl.
compile(JavaFXScriptEngineImpl.java:119)
at com.sun.tools.javafx.script.JavaFXScriptEngineImpl.
compile(JavaFXScriptEngineImpl.java:110)
at FXCompile.main(FXCompile.java:45)