Module jdk.jshell

Package jdk.jshell.spi

Interface ExecutionControl

All Superinterfaces:

AutoCloseable

All Known Implementing Classes:

DirectExecutionControl, JdiDefaultExecutionControl, JdiExecutionControl, LocalExecutionControl, RemoteExecutionControl, StreamingExecutionControl

public interface ExecutionControl
extends AutoCloseable

This interface specifies the functionality that must provided to implement a pluggable JShell execution engine.

The audience for this Service Provider Interface is engineers wishing to implement their own version of the execution engine in support of the JShell API.

A Snippet is compiled into code wrapped in a 'wrapper class'. The execution engine is used by the core JShell implementation to load and, for executable Snippets, execute the Snippet.

Methods defined in this interface should only be called by the core JShell implementation.

Since:

9

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static class	ExecutionControl.ClassBytecodes	Bundles class name with class bytecodes.
static class	ExecutionControl.ClassInstallException	A class install (load or redefine) encountered a problem.
static class	ExecutionControl.EngineTerminationException	Unbidden execution engine termination has occurred.
static class	ExecutionControl.ExecutionControlException	The abstract base of all ExecutionControl exceptions.
static class	ExecutionControl.InternalException	An internal problem has occurred.
static class	ExecutionControl.NotImplementedException	The command is not implemented.
static class	ExecutionControl.ResolutionException	An exception indicating that a DeclarationSnippet with unresolved references has been encountered.
static class	ExecutionControl.RunException	The abstract base of of exceptions specific to running user code.
static class	ExecutionControl.StoppedException	An exception indicating that an invoke(java.lang.String, java.lang.String) (or theoretically a varValue(java.lang.String, java.lang.String)) has been interrupted by a stop().
static class	ExecutionControl.UserException	A 'normal' user exception occurred.

Method Summary

Modifier and Type	Method	Description
void	addToClasspath(String path)	Adds the path to the execution class path.
void	close()	Shuts down this execution engine.
Object	extensionCommand(String command, Object arg)	Run a non-standard command (or a standard command from a newer version).
static ExecutionControl	generate(ExecutionEnv env, String spec)	Search for a provider, then create and return the ExecutionControl instance.
static ExecutionControl	generate(ExecutionEnv env, String name, Map<String,String> parameters)	Search for a provider, then create and return the ExecutionControl instance.
String	invoke(String className, String methodName)	Invokes an executable Snippet by calling a method on the specified wrapper class.
void	load(ExecutionControl.ClassBytecodes[] cbcs)	Attempts to load new classes.
void	redefine(ExecutionControl.ClassBytecodes[] cbcs)	Attempts to redefine previously loaded classes.
void	stop()	Interrupts a running invoke.
String	varValue(String className, String varName)	Returns the value of a variable.

Method Detail

load

void load(ExecutionControl.ClassBytecodes[] cbcs)
   throws ExecutionControl.ClassInstallException,
          ExecutionControl.NotImplementedException,
          ExecutionControl.EngineTerminationException

Attempts to load new classes.

Parameters:

cbcs - the class name and bytecodes to load

Throws:

ExecutionControl.ClassInstallException - exception occurred loading the classes, some or all were not loaded

ExecutionControl.NotImplementedException - if not implemented

ExecutionControl.EngineTerminationException - the execution engine has terminated

redefine

void redefine(ExecutionControl.ClassBytecodes[] cbcs)
       throws ExecutionControl.ClassInstallException,
              ExecutionControl.NotImplementedException,
              ExecutionControl.EngineTerminationException

Attempts to redefine previously loaded classes.

Parameters:

cbcs - the class name and bytecodes to redefine

Throws:

ExecutionControl.ClassInstallException - exception occurred redefining the classes, some or all were not redefined

ExecutionControl.NotImplementedException - if not implemented

ExecutionControl.EngineTerminationException - the execution engine has terminated

invoke

String invoke(String className,
              String methodName)
       throws ExecutionControl.RunException,
              ExecutionControl.EngineTerminationException,
              ExecutionControl.InternalException

Invokes an executable Snippet by calling a method on the specified wrapper class. The method must have no arguments and return String.

Parameters:

className - the class whose method should be invoked

methodName - the name of method to invoke

Returns:

the result of the execution or null if no result

Throws:

ExecutionControl.UserException - the invoke raised a user exception

ExecutionControl.ResolutionException - the invoke attempted to directly or indirectly invoke an unresolved snippet

ExecutionControl.StoppedException - if the invoke() was canceled by stop()

ExecutionControl.EngineTerminationException - the execution engine has terminated

ExecutionControl.InternalException - an internal problem occurred

ExecutionControl.RunException

varValue

String varValue(String className,
                String varName)
         throws ExecutionControl.RunException,
                ExecutionControl.EngineTerminationException,
                ExecutionControl.InternalException

Returns the value of a variable.

Parameters:

className - the name of the wrapper class of the variable

varName - the name of the variable

Returns:

the value of the variable

Throws:

ExecutionControl.UserException - formatting the value raised a user exception

ExecutionControl.ResolutionException - formatting the value attempted to directly or indirectly invoke an unresolved snippet

ExecutionControl.StoppedException - if the formatting the value was canceled by stop()

ExecutionControl.EngineTerminationException - the execution engine has terminated

ExecutionControl.InternalException - an internal problem occurred

ExecutionControl.RunException

addToClasspath

void addToClasspath(String path)
             throws ExecutionControl.EngineTerminationException,
                    ExecutionControl.InternalException

Adds the path to the execution class path.

Parameters:

path - the path to add

Throws:

ExecutionControl.EngineTerminationException - the execution engine has terminated

ExecutionControl.InternalException - an internal problem occurred

stop

void stop()
   throws ExecutionControl.EngineTerminationException,
          ExecutionControl.InternalException

Interrupts a running invoke.

Throws:

ExecutionControl.EngineTerminationException - the execution engine has terminated

ExecutionControl.InternalException - an internal problem occurred

extensionCommand

Object extensionCommand(String command,
                        Object arg)
                 throws ExecutionControl.RunException,
                        ExecutionControl.EngineTerminationException,
                        ExecutionControl.InternalException

Run a non-standard command (or a standard command from a newer version).

Parameters:

command - the non-standard command

arg - the commands argument

Returns:

the commands return value

Throws:

ExecutionControl.UserException - the command raised a user exception

ExecutionControl.ResolutionException - the command attempted to directly or indirectly invoke an unresolved snippet

ExecutionControl.StoppedException - if the command was canceled by stop()

ExecutionControl.EngineTerminationException - the execution engine has terminated

ExecutionControl.NotImplementedException - if not implemented

ExecutionControl.InternalException - an internal problem occurred

ExecutionControl.RunException

close

void close()

Shuts down this execution engine. Implementation should free all resources held by this execution engine.

No calls to methods on this interface should be made after close.

Specified by:

close in interface AutoCloseable

generate

static ExecutionControl generate(ExecutionEnv env,
                                 String name,
                                 Map<String,String> parameters)
                          throws Throwable

Search for a provider, then create and return the ExecutionControl instance.

Parameters:

env - the execution environment (provided by JShell)

name - the name of provider

parameters - the parameter map.

Returns:

the execution engine

Throws:

Throwable - an exception that occurred attempting to find or create the execution engine.

IllegalArgumentException - if no ExecutionControlProvider has the specified name and parameters.

generate

static ExecutionControl generate(ExecutionEnv env,
                                 String spec)
                          throws Throwable

Search for a provider, then create and return the ExecutionControl instance.

Parameters:

env - the execution environment (provided by JShell)

spec - the ExecutionControl spec, which is described in the documentation of this package documentation.

Returns:

the execution engine

Throws:

Throwable - an exception that occurred attempting to find or create the execution engine.

IllegalArgumentException - if no ExecutionControlProvider has the specified name and parameters.

IllegalArgumentException - if spec is malformed