org.apache.bsf.engines.netrexx

Class NetRexxEngine

java.lang.Object

org.apache.bsf.util.BSFEngineImpl

org.apache.bsf.engines.netrexx.NetRexxEngine

All Implemented Interfaces:

java.beans.PropertyChangeListener, java.util.EventListener, BSFEngine

public class NetRexxEngine
extends BSFEngineImpl

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.

Field Summary

Fields inherited from class org.apache.bsf.util.BSFEngineImpl

classLoader, classPath, declaredBeans, lang, mgr, tempDir

Constructor Summary

Constructors

Constructor and Description
NetRexxEngine() Constructor.

Method Summary

Modifier and Type	Method and Description
java.lang.Object	call(java.lang.Object object, java.lang.String method, java.lang.Object[] args) Return an object from an extension.
void	declareBean(BSFDeclaredBean bean) Declare a bean after the engine has been started.
java.lang.Object	eval(java.lang.String source, int lineNo, int columnNo, java.lang.Object script) Override impl of execute.
void	exec(java.lang.String source, int lineNo, int columnNo, java.lang.Object script) Override impl of execute.
java.lang.Object	execEvalShared(java.lang.String source, int lineNo, int columnNo, java.lang.Object oscript, boolean returnsObject) This is shared code for the exec() and eval() operations.
void	initialize(BSFManager mgr, java.lang.String lang, java.util.Vector declaredBeans) initialize the engine; called right after construction by the manager.
void	undeclareBean(BSFDeclaredBean bean) Undeclare a previously declared bean.

Methods inherited from class org.apache.bsf.util.BSFEngineImpl

apply, compileApply, compileExpr, compileScript, iexec, propertyChange, terminate

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

NetRexxEngine

public NetRexxEngine()

Constructor.

Method Detail

call

public java.lang.Object call(java.lang.Object object,
                             java.lang.String method,
                             java.lang.Object[] args)
                      throws BSFException

Return an object from an extension.

Parameters:

object - object from which to call our static method

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.

Throws:

BSFException - if anything goes wrong while eval'ing a BSFException is thrown. The reason indicates the problem.

declareBean

public void declareBean(BSFDeclaredBean bean)
                 throws BSFException

Description copied from interface: BSFEngine

Declare a bean after the engine has been started. Declared beans are beans that are named and which the engine must make available to the scripts it runs in the most first class way possible.

Specified by:

declareBean in interface BSFEngine

Overrides:

declareBean in class BSFEngineImpl

Parameters:

bean - the bean to declare

Throws:

BSFException - if the engine cannot do this operation

eval

public java.lang.Object eval(java.lang.String source,
                             int lineNo,
                             int columnNo,
                             java.lang.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.

Parameters:

source - (context info) the source of this expression (e.g., filename)

lineNo - (context info) the line number in source for expr

columnNo - (context info) the column number in source for expr

script - the expression to evaluate

Throws:

BSFException - if anything goes wrong while eval'ing a BSFException is thrown. The reason indicates the problem.

exec

public void exec(java.lang.String source,
                 int lineNo,
                 int columnNo,
                 java.lang.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.

Specified by:

exec in interface BSFEngine

Overrides:

exec in class BSFEngineImpl

Parameters:

source - (context info) the source of this expression (e.g., filename)

lineNo - (context info) the line number in source for expr

columnNo - (context info) the column number in source for expr

script - the script to execute

Throws:

BSFException - if anything goes wrong while exec'ing a BSFException is thrown. The reason indicates the problem.

execEvalShared

public java.lang.Object execEvalShared(java.lang.String source,
                                       int lineNo,
                                       int columnNo,
                                       java.lang.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.

Throws:

BSFException

initialize

public void initialize(BSFManager mgr,
                       java.lang.String lang,
                       java.util.Vector declaredBeans)
                throws BSFException

Description copied from class: BSFEngineImpl

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.

Specified by:

initialize in interface BSFEngine

Overrides:

initialize in class BSFEngineImpl

Parameters:

mgr - The BSFManager that's hosting this engine.

lang - Language string which this engine is handling.

declaredBeans - Vector of BSFDeclaredObject containing beans that should be declared into the language runtime at init time as best as possible.

Throws:

BSFException - if anything goes wrong while init'ing a BSFException is thrown. The reason indicates the problem.

undeclareBean

public void undeclareBean(BSFDeclaredBean bean)
                   throws BSFException

Description copied from interface: BSFEngine

Undeclare a previously declared bean.

Specified by:

undeclareBean in interface BSFEngine

Overrides:

undeclareBean in class BSFEngineImpl

Parameters:

bean - the bean to undeclare

Throws:

BSFException - if the engine cannot do this operation