ScriptEngineManager (Java SE 12 & JDK 12 )
Keywords: javax.script.ScriptEngineManager class

Module java.scripting
Package javax.script

## Class ScriptEngineManager

- java.lang.Object
- - javax.script.ScriptEngineManager

-     public class ScriptEngineManager
      extends Object

  The `ScriptEngineManager` implements a discovery and instantiation mechanism for `ScriptEngine` classes and also maintains a collection of key/value pairs storing state shared by all engines created by the Manager. This class uses the service provider mechanism described in the `ServiceLoader` class to enumerate all the implementations of `ScriptEngineFactory`.
  The `ScriptEngineManager` provides a method to return a list of all these factories as well as utility methods which look up factories on the basis of language name, file extension and mime type.

  The `Bindings` of key/value pairs, referred to as the "Global Scope" maintained by the manager is available to all instances of `ScriptEngine` created by the `ScriptEngineManager`. The values in the `Bindings` are generally exposed in all scripts.

  Since:
    1.6

- - ### Constructor Summary

    Constructors
    Constructor | Description
    --- | ---
    `ScriptEngineManager()` | The effect of calling this constructor is the same as calling `ScriptEngineManager(Thread.currentThread().getContextClassLoader())`.
    `ScriptEngineManager​(ClassLoader loader)` | This constructor loads the implementations of `ScriptEngineFactory` visible to the given `ClassLoader` using the service provider mechanism. If loader is `null`, the script engine factories that are bundled with the platform are loaded.

  - ### Method Summary

    Modifier and Type | Method | Description
    --- | --- | ---
    `Object` | `get​(String key)` | Gets the value for the specified key in the Global Scope
    `Bindings` | `getBindings()` | `getBindings` returns the value of the `globalScope` field.
    `ScriptEngine` | `getEngineByExtension​(String extension)` | Look up and create a `ScriptEngine` for a given extension.
    `ScriptEngine` | `getEngineByMimeType​(String mimeType)` | Look up and create a `ScriptEngine` for a given mime type.
    `ScriptEngine` | `getEngineByName​(String shortName)` | Looks up and creates a `ScriptEngine` for a given name.
    `List<ScriptEngineFactory>` | `getEngineFactories()` | Returns a list whose elements are instances of all the `ScriptEngineFactory` classes found by the discovery mechanism.
    `void` | `put​(String key, Object value)` | Sets the specified key/value pair in the Global Scope.
    `void` | `registerEngineExtension​(String extension, ScriptEngineFactory factory)` | Registers a `ScriptEngineFactory` to handle an extension.
    `void` | `registerEngineMimeType​(String type, ScriptEngineFactory factory)` | Registers a `ScriptEngineFactory` to handle a mime type.
    `void` | `registerEngineName​(String name, ScriptEngineFactory factory)` | Registers a `ScriptEngineFactory` to handle a language name.
    `void` | `setBindings​(Bindings bindings)` | `setBindings` stores the specified `Bindings` in the `globalScope` field.

    - ### Methods declared in class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### ScriptEngineManager

          public ScriptEngineManager()

      The effect of calling this constructor is the same as calling `ScriptEngineManager(Thread.currentThread().getContextClassLoader())`.
      See Also:
        `Thread.getContextClassLoader()`

    - #### ScriptEngineManager

          public ScriptEngineManager​(ClassLoader loader)

      This constructor loads the implementations of `ScriptEngineFactory` visible to the given `ClassLoader` using the service provider mechanism.
      If loader is `null`, the script engine factories that are bundled with the platform are loaded.
      Parameters:
        `loader` - ClassLoader used to discover script engine factories.

  - ### Method Detail

    - #### setBindings

          public void setBindings​(Bindings bindings)

      `setBindings` stores the specified `Bindings` in the `globalScope` field. ScriptEngineManager sets this `Bindings` as global bindings for `ScriptEngine` objects created by it.
      Parameters:
        `bindings` - The specified `Bindings`
      Throws:
        `IllegalArgumentException` - if bindings is null.

    - #### getBindings

          public Bindings getBindings()

      `getBindings` returns the value of the `globalScope` field. ScriptEngineManager sets this `Bindings` as global bindings for `ScriptEngine` objects created by it.
      Returns:
        The globalScope field.

    - #### put

          public void put​(String key,
                          Object value)

      Sets the specified key/value pair in the Global Scope.
      Parameters:
        `key` - Key to set
        `value` - Value to set.
      Throws:
        `NullPointerException` - if key is null.
        `IllegalArgumentException` - if key is empty string.

    - #### get

          public Object get​(String key)

      Gets the value for the specified key in the Global Scope
      Parameters:
        `key` - The key whose value is to be returned.
      Returns:
        The value for the specified key.

    - #### getEngineByName

          public ScriptEngine getEngineByName​(String shortName)

      Looks up and creates a `ScriptEngine` for a given name. The algorithm first searches for a `ScriptEngineFactory` that has been registered as a handler for the specified name using the `registerEngineName` method.
      If one is not found, it searches the set of `ScriptEngineFactory` instances stored by the constructor for one with the specified name. If a `ScriptEngineFactory` is found by either method, it is used to create instance of `ScriptEngine`.
      Parameters:
        `shortName` - The short name of the `ScriptEngine` implementation. returned by the `getNames` method of its `ScriptEngineFactory`.
      Returns:
        A `ScriptEngine` created by the factory located in the search. Returns null if no such factory was found. The `ScriptEngineManager` sets its own `globalScope` `Bindings` as the `GLOBAL_SCOPE` `Bindings` of the newly created `ScriptEngine`.
      Throws:
        `NullPointerException` - if shortName is null.

    - #### getEngineByExtension

          public ScriptEngine getEngineByExtension​(String extension)

      Look up and create a `ScriptEngine` for a given extension. The algorithm used by `getEngineByName` is used except that the search starts by looking for a `ScriptEngineFactory` registered to handle the given extension using `registerEngineExtension`.
      Parameters:
        `extension` - The given extension
      Returns:
        The engine to handle scripts with this extension. Returns `null` if not found.
      Throws:
        `NullPointerException` - if extension is null.

    - #### getEngineByMimeType

          public ScriptEngine getEngineByMimeType​(String mimeType)

      Look up and create a `ScriptEngine` for a given mime type. The algorithm used by `getEngineByName` is used except that the search starts by looking for a `ScriptEngineFactory` registered to handle the given mime type using `registerEngineMimeType`.
      Parameters:
        `mimeType` - The given mime type
      Returns:
        The engine to handle scripts with this mime type. Returns `null` if not found.
      Throws:
        `NullPointerException` - if mimeType is null.

    - #### getEngineFactories

          public List<ScriptEngineFactory> getEngineFactories()

      Returns a list whose elements are instances of all the `ScriptEngineFactory` classes found by the discovery mechanism.
      Returns:
        List of all discovered `ScriptEngineFactory`s.

    - #### registerEngineName

          public void registerEngineName​(String name,
                                         ScriptEngineFactory factory)

      Registers a `ScriptEngineFactory` to handle a language name. Overrides any such association found using the Discovery mechanism.
      Parameters:
        `name` - The name to be associated with the `ScriptEngineFactory`.
        `factory` - The class to associate with the given name.
      Throws:
        `NullPointerException` - if any of the parameters is null.

    - #### registerEngineMimeType

          public void registerEngineMimeType​(String type,
                                             ScriptEngineFactory factory)

      Registers a `ScriptEngineFactory` to handle a mime type. Overrides any such association found using the Discovery mechanism.
      Parameters:
        `type` - The mime type to be associated with the `ScriptEngineFactory`.
        `factory` - The class to associate with the given mime type.
      Throws:
        `NullPointerException` - if any of the parameters is null.

    - #### registerEngineExtension

          public void registerEngineExtension​(String extension,
                                              ScriptEngineFactory factory)

      Registers a `ScriptEngineFactory` to handle an extension. Overrides any such association found using the Discovery mechanism.
      Parameters:
        `extension` - The extension type to be associated with the `ScriptEngineFactory`.
        `factory` - The class to associate with the given extension.
      Throws:
        `NullPointerException` - if any of the parameters is null.