javax.script

## Interface ScriptEngineFactory

-     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 mechanism described in the Jar File Specification to obtain instances of all `ScriptEngineFactories` available in the current ClassLoader.
  Since:
    1.6

- - ### Method Summary

    Methods
    Modifier and Type | Method and 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"}.

    - #### 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.NAME
      - ScriptEngine.LANGUAGE
      - ScriptEngine.LANGUAGE_VERSION

      The values for these keys are the Strings returned by `getEngineName`, `getEngineVersion`, `getName`, `getLanguageName` and `getLanguageVersion` respectively.
      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.

    - #### 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.

    - #### 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

    - #### 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.

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