Interface ScriptEngineFactory

All Known Implementing Classes:: NashornScriptEngineFactory

public interface ScriptEngineFactory

ScriptEngineFactory is used to describe and instantiate ScriptEngines.

Each class implementing ScriptEngine has a corresponding factory that exposes metadata describing the engine class.

The ScriptEngineManager uses the service-provider loader mechanism described in the ServiceLoader class to obtain instances of ScriptEngineFactory instances. See ScriptEngineManager() and ScriptEngineManager(java.lang.ClassLoader).

Since:: 1.6

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`String`	`getEngineName()`	Returns the full name of the `ScriptEngine`.
`String`	`getEngineVersion()`	Returns the version of the `ScriptEngine`.
`List<String>`	`getExtensions()`	Returns an immutable list of filename extensions, which generally identify scripts written in the language supported by this `ScriptEngine`.
`String`	`getLanguageName()`	Returns the name of the scripting language supported by this `ScriptEngine`.
`String`	`getLanguageVersion()`	Returns the version of the scripting language supported by this `ScriptEngine`.
`String`	`getMethodCallSyntax(String obj, String m, String... args)`	Returns a String which can be used to invoke a method of a Java object using the syntax of the supported scripting language.
`List<String>`	`getMimeTypes()`	Returns an immutable list of mimetypes, associated with scripts that can be executed by the engine.
`List<String>`	`getNames()`	Returns an immutable list of short names for the `ScriptEngine`, which may be used to identify the `ScriptEngine` by the `ScriptEngineManager`.
`String`	`getOutputStatement(String toDisplay)`	Returns a String that can be used as a statement to display the specified String using the syntax of the supported scripting language.
`Object`	`getParameter(String key)`	Returns the value of an attribute whose meaning may be implementation-specific.
`String`	`getProgram(String... statements)`	Returns a valid scripting language executable program with given statements.
`ScriptEngine`	`getScriptEngine()`	Returns an instance of the `ScriptEngine` associated with this `ScriptEngineFactory`.

Method Detail

getEngineName

String getEngineName()

Returns the full name of the ScriptEngine. For instance an implementation based on the Mozilla Rhino Javascript engine might return Rhino Mozilla Javascript Engine.

Returns:: The name of the engine implementation.

getEngineVersion

String getEngineVersion()

Returns the version of the ScriptEngine.

Returns:: The ScriptEngine implementation version.

getExtensions

List<String> getExtensions()

Returns an immutable list of filename extensions, which generally identify scripts written in the language supported by this ScriptEngine. The array is used by the ScriptEngineManager to implement its getEngineByExtension method.

Returns:: The list of extensions.

getMimeTypes

List<String> getMimeTypes()

Returns an immutable list of mimetypes, associated with scripts that can be executed by the engine. The list is used by the ScriptEngineManager class to implement its getEngineByMimetype method.

Returns:: The list of mime types.

getNames

List<String> getNames()

Returns an immutable list of short names for the ScriptEngine, which may be used to identify the ScriptEngine by the ScriptEngineManager. For instance, an implementation based on the Mozilla Rhino Javascript engine might return list containing {"javascript", "rhino"}.

Returns:: an immutable list of short names

getLanguageName

String getLanguageName()

Returns the name of the scripting language supported by this ScriptEngine.

Returns:: The name of the supported language.

getLanguageVersion

String getLanguageVersion()

Returns the version of the scripting language supported by this ScriptEngine.

Returns:: The version of the supported language.

getParameter

Object getParameter(String key)

Returns the value of an attribute whose meaning may be implementation-specific. Keys for which the value is defined in all implementations are:

ScriptEngine.ENGINE
ScriptEngine.ENGINE_VERSION
ScriptEngine.LANGUAGE
ScriptEngine.LANGUAGE_VERSION
ScriptEngine.NAME

The values for these keys are the Strings returned by getEngineName, getEngineVersion, getLanguageName, getLanguageVersion for the first four keys respectively. For NAME, one of the Strings returned by getNames is returned.

A reserved key, THREADING, whose value describes the behavior of the engine with respect to concurrent execution of scripts and maintenance of state is also defined. These values for the THREADING key are:

null - The engine implementation is not thread safe, and cannot be used to execute scripts concurrently on multiple threads.
"MULTITHREADED" - The engine implementation is internally thread-safe and scripts may execute concurrently although effects of script execution on one thread may be visible to scripts on other threads.
"THREAD-ISOLATED" - The implementation satisfies the requirements of "MULTITHREADED", and also, the engine maintains independent values for symbols in scripts executing on different threads.
"STATELESS" - The implementation satisfies the requirements of "THREAD-ISOLATED". In addition, script executions do not alter the mappings in the Bindings which is the engine scope of the ScriptEngine. In particular, the keys in the Bindings and their associated values are the same before and after the execution of the script.

Implementations may define implementation-specific keys.

Parameters:: key - The name of the parameter
Returns:: The value for the given parameter. Returns null if no value is assigned to the key.
Throws:: NullPointerException - if the key is null.

getMethodCallSyntax

String getMethodCallSyntax(String obj,
                           String m,
                           String... args)

Returns a String which can be used to invoke a method of a Java object using the syntax of the supported scripting language. For instance, an implementation for a Javascript engine might be;

public String getMethodCallSyntax(String obj,
                                   String m, String... args) {
      String ret = obj;
      ret += "." + m + "(";
      for (int i = 0; i < args.length; i++) {
          ret += args[i];
          if (i < args.length - 1) {
              ret += ",";
          }
      }
      ret += ")";
      return ret;
 }

Parameters:: obj - The name representing the object whose method is to be invoked. The name is the one used to create bindings using the put method of ScriptEngine, the put method of an ENGINE_SCOPE Bindings,or the setAttribute method of ScriptContext. The identifier used in scripts may be a decorated form of the specified one.; m - The name of the method to invoke.; args - names of the arguments in the method call.
Returns:: The String used to invoke the method in the syntax of the scripting language.
Throws:: NullPointerException - if obj or m or args or any of the elements of args is null.

getOutputStatement

String getOutputStatement(String toDisplay)

Returns a String that can be used as a statement to display the specified String using the syntax of the supported scripting language. For instance, the implementation for a Perl engine might be;

public String getOutputStatement(String toDisplay) {
      return "print(" + toDisplay + ")";
 }

Parameters:: toDisplay - The String to be displayed by the returned statement.
Returns:: The string used to display the String in the syntax of the scripting language.

getProgram

String getProgram(String... statements)

Returns a valid scripting language executable program with given statements. For instance an implementation for a PHP engine might be:

public String getProgram(String... statements) {
      String retval = "<?\n";
      int len = statements.length;
      for (int i = 0; i < len; i++) {
          retval += statements[i] + ";\n";
      }
      return retval += "?>";
 }

Parameters:: statements - The statements to be executed. May be return values of calls to the getMethodCallSyntax and getOutputStatement methods.
Returns:: The Program
Throws:: NullPointerException - if the statements array or any of its elements is null

getScriptEngine

ScriptEngine getScriptEngine()

Returns an instance of the ScriptEngine associated with this ScriptEngineFactory. A new ScriptEngine is generally returned, but implementations may pool, share or reuse engines.

Returns:: A new ScriptEngine instance.