This is the interface to NetRexx from the
Bean Scripting Framework.
The NetRexx code must be written script-style, without a "class" or
"properties" section preceeding the executable code. The NetRexxEngine will
generate a prefix for this code:
class $$CLASSNAME$$;
method BSFNetRexxEngineEntry(bsf=org.apache.bsf.BSFManager) public static;
$$CLASSNAME$$ will be replaced by a generated classname of the form
BSFNetRexx*, and the bsf parameter can be used to retrieve application
objects registered with the Bean Scripting Framework.
If you use the placeholder string $$CLASSNAME$$ elsewhere
in your script -- including within text strings -- BSFNetRexxEngine will
replace it with the generated name of the class before the NetRexx code
is compiled.
If you need to use full NetRexx functionality, we recommend that your
NetRexx script define and invoke a "minor class", with or without the
"dependent" keyword as suits your needs. You'll have to use $$CLASSNAME$$
in naming the minor class, since the name of the main class is synthesized;
for example, to create the minor class "bar" you'd write
"class $$CLASSNAME$$.Bar".
Hazards:
Since NetRexx has to be _compiled_ to a Java classfile, invoking it involves
a fair amount of computation to load and execute the compiler. We are
currently making an attempt to manage that by caching the class
after it has been loaded, but the indexing is fairly primitive; we
hash against the script string to find the class for it.
Minor-class .class files are now being deleted after the major class loads.
This coould potentially cause problems.
call
public Object call(Object object,
String method,
Object[] args)
throws BSFException
Return an object from an extension.
- call in interface BSFEngine
method
- The name of the method to call.args
- an array of arguments to be
passed to the extension, which may be either
Vectors of Nodes, or Strings.
eval
public Object eval(String source,
int lineNo,
int columnNo,
Object script)
throws BSFException
Override impl of execute. In NetRexx, methods which do not wish
to return a value should be invoked via exec, which will cause them
to be generated without the "returns" clause.
Those which wish to return a value should call eval instead.
which will add "returns java.lang.Object" to the header.
Note: It would be nice to have the "real" return type avaialable, so
we could do something more type-safe than Object, and so we could
return primitive types without having to enclose them in their
object wrappers. BSF does not currently support that concept.
- eval in interface BSFEngine
exec
public void exec(String source,
int lineNo,
int columnNo,
Object script)
throws BSFException
Override impl of execute. In NetRexx, methods which do not wish
to return a value should be invoked via exec, which will cause them
to be generated without the "returns" clause.
Those which wish to return a value should call eval instead.
which will add "returns java.lang.Object" to the header.
- exec in interface BSFEngine
- exec in interface BSFEngineImpl
execEvalShared
public Object execEvalShared(String source,
int lineNo,
int columnNo,
Object oscript,
boolean returnsObject)
throws BSFException
This is shared code for the exec() and eval() operations. It will
evaluate a string containing a NetRexx method body -- which may be
as simple as a single return statement.
It should store the "bsf" handle where the
script can get to it, for callback purposes.
Note that NetRexx compilation imposes serious overhead -- 11 seconds for
the first compile, about 3 thereafter -- but in exchange you get
Java-like speeds once the classes have been created (minus the cache
lookup cost).
Nobody knows whether javac is threadsafe.
I'm going to serialize access to the compilers to protect it.
initialize
public void initialize(BSFManager mgr,
String lang,
Vector declaredBeans)
throws BSFException
initialize the engine; called right after construction by
the manager. Declared beans are simply kept in a vector and
that's it. Subclasses must do whatever they want with it.
- initialize in interface BSFEngine
- initialize in interface BSFEngineImpl