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/OpenJDK 21

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

Modifier and Type Interface Description
static final 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 Details

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

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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
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https://docs.oracle.com/en/java/javase/21/docs/api/jdk.jshell/jdk/jshell/spi/ExecutionControl.html