Package org.apache.bsf.engines.netrexx

Class NetRexxEngine

java.lang.Object
org.apache.bsf.util.BSFEngineImpl
org.apache.bsf.engines.netrexx.NetRexxEngine
All Implemented Interfaces:
PropertyChangeListener, 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.

Author:
Joe Kesselman, Sanjiva Weerawarana, Rony G. Flatscher (added BSF_Log[Factory] to allow BSF to run without org.apache.commons.logging present)

  • Constructor Details

    • NetRexxEngine

      public NetRexxEngine()
      Constructor.

  • Method Details

    • call

      public Object call(Object object, String method, 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 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.
      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(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.
      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 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.

      Throws:
      BSFException

    • initialize

      public void initialize(BSFManager mgr, String lang, 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