Package org.apache.bsf

# Interface BSFEngine

All Superinterfaces:
  `EventListener`, `PropertyChangeListener`

All Known Implementing Classes:
  `BSFEngineImpl`, `fakeEngine`, `JaclEngine`, `JavaClassEngine`, `JavaEngine`, `JavaScriptEngine`, `JythonEngine`, `NetRexxEngine`, `XSLTEngine`

public interface BSFEngine extends PropertyChangeListener
This is the view of a scripting engine assumed by the Bean Scripting Framework. This interface is used when an application decides to run some script under application control. (This is the reverse of the more common situation, which is that of the scripting language calling into the application.)

When a scripting engine is first fired up, the initialize() method is called right after construction.

A scripting engine must provide two access points for applications to call into them: via function calls and via expression evaluation. It must also support loading scripts.

A scripting engine is a property change listener and will be notified when any of the relevant properties of the manager change. (See BSFManager to see which of its properties are bound.)

Author:
  Sanjiva Weerawarana, Matthew J. Duftler

- ## Method Summary

  Modifier and Type
  Method
  Description
  `Object`
  `apply(String source, int lineNo, int columnNo, Object funcBody, Vector paramNames, Vector arguments)`
  This is used by an application to invoke an anonymous function.
  `Object`
  `call(Object object, String name, Object[] args)`
  This is used by an application to call into the scripting engine to make a function/method call.
  `void`
  `compileApply(String source, int lineNo, int columnNo, Object funcBody, Vector paramNames, Vector arguments, CodeBuffer cb)`
  This is used by an application to compile an anonymous function.
  `void`
  `compileExpr(String source, int lineNo, int columnNo, Object expr, CodeBuffer cb)`
  This is used by an application to compile a value-returning expression.
  `void`
  `compileScript(String source, int lineNo, int columnNo, Object script, CodeBuffer cb)`
  This is used by an application to compile some script.
  `void`
  `declareBean(BSFDeclaredBean bean)`
  Declare a bean after the engine has been started.
  `Object`
  `eval(String source, int lineNo, int columnNo, Object expr)`
  This is used by an application to evaluate an expression.
  `void`
  `exec(String source, int lineNo, int columnNo, Object script)`
  This is used by an application to execute some script.
  `void`
  `iexec(String source, int lineNo, int columnNo, Object script)`
  This is used by an application to execute some script, as though one were interacting with the language in an interactive session.
  `void`
  `initialize(BSFManager mgr, String lang, Vector declaredBeans)`
  This method is used to initialize the engine right after construction.
  `void`
  `terminate()`
  Graceful termination
  `void`
  `undeclareBean(BSFDeclaredBean bean)`
  Undeclare a previously declared bean.

  ### Methods inherited from interface java.beans.PropertyChangeListener

  `propertyChange`

- ## Method Details

  - ### apply

    Object apply(String source, int lineNo, int columnNo, Object funcBody, Vector paramNames, Vector arguments) throws BSFException
    This is used by an application to invoke an anonymous function. An anonymous function is a multi-line script which when evaluated will produce a value. These are separated from expressions and scripts because the prior are spsed to be good 'ol expressions and scripts are not value returning. We allow anonymous functions to have parameters as well for completeness.
    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
      `funcBody` - the multi-line, value returning script to evaluate
      `paramNames` - the names of the parameters above assumes
      `arguments` - values of the above parameters
    Throws:
      `BSFException` - if anything goes wrong while doin' it.

  - ### call

    Object call(Object object, String name, Object[] args) throws BSFException
    This is used by an application to call into the scripting engine to make a function/method call. The "object" argument is the object whose method is to be called, if that applies. For non-OO languages, this is typically ignored and should be given as null. For pretend-OO languages such as VB, this would be the (String) name of the object. The arguments are given in the args array.
    Parameters:
      `object` - object on which to make the call
      `name` - name of the method / procedure to call
      `args` - the arguments to be given to the procedure
    Throws:
      `BSFException` - if anything goes wrong while eval'ing a BSFException is thrown. The reason indicates the problem.

  - ### compileApply

    void compileApply(String source, int lineNo, int columnNo, Object funcBody, Vector paramNames, Vector arguments, CodeBuffer cb) throws BSFException
    This is used by an application to compile an anonymous function. See comments in apply for more hdetails.
    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
      `funcBody` - the multi-line, value returning script to evaluate
      `paramNames` - the names of the parameters above assumes
      `arguments` - values of the above parameters
      `cb` - the CodeBuffer to compile into
    Throws:
      `BSFException` - if anything goes wrong while doin' it.

  - ### compileExpr

    void compileExpr(String source, int lineNo, int columnNo, Object expr, CodeBuffer cb) throws BSFException
    This is used by an application to compile a value-returning expression. The expr may be string or some other type, depending on the language. The generated code is dumped into the `CodeBuffer`.
    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
      `expr` - the expression to compile
      `cb` - the CodeBuffer to compile into
    Throws:
      `BSFException` - if anything goes wrong while compiling a BSFException is thrown. The reason indicates the problem.

  - ### compileScript

    void compileScript(String source, int lineNo, int columnNo, Object script, CodeBuffer cb) throws BSFException
    This is used by an application to compile some script. The script may be string or some other type, depending on the language. The generated code is dumped into the `CodeBuffer`.
    Parameters:
      `source` - (context info) the source of this script (e.g., filename)
      `lineNo` - (context info) the line number in source for script
      `columnNo` - (context info) the column number in source for script
      `script` - the script to compile
      `cb` - the CodeBuffer to compile into
    Throws:
      `BSFException` - if anything goes wrong while compiling a BSFException is thrown. The reason indicates the problem.

  - ### declareBean

    void declareBean(BSFDeclaredBean bean) throws BSFException
    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.
    Parameters:
      `bean` - the bean to declare
    Throws:
      `BSFException` - if the engine cannot do this operation

  - ### eval

    Object eval(String source, int lineNo, int columnNo, Object expr) throws BSFException
    This is used by an application to evaluate an expression. The expression may be string or some other type, depending on the language. (For example, for BML it'll be an org.w3c.dom.Element object.)
    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
      `expr` - the expression to evaluate
    Throws:
      `BSFException` - if anything goes wrong while eval'ing a BSFException is thrown. The reason indicates the problem.

  - ### exec

    void exec(String source, int lineNo, int columnNo, Object script) throws BSFException
    This is used by an application to execute some script. The expression may be string or some other type, depending on the language. Returns nothing but if something goes wrong it excepts (of course).
    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.

  - ### iexec

    void iexec(String source, int lineNo, int columnNo, Object script) throws BSFException
    This is used by an application to execute some script, as though one were interacting with the language in an interactive session. The expression may be string or some other type, depending on the language. Returns nothing but if something goes wrong it excepts (of course).
    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.

  - ### initialize

    void initialize(BSFManager mgr, String lang, Vector declaredBeans) throws BSFException
    This method is used to initialize the engine right after construction. This method will be called before any calls to eval or call. At this time the engine should capture the current values of interesting properties from the manager. In the future, any changes to those will be mirrored to me by the manager via a property change event.
    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.

  - ### terminate

    void terminate()
    Graceful termination

  - ### undeclareBean

    void undeclareBean(BSFDeclaredBean bean) throws BSFException
    Undeclare a previously declared bean.
    Parameters:
      `bean` - the bean to undeclare
    Throws:
      `BSFException` - if the engine cannot do this operation