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package javax.script;

import java.util.List;


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(ClassLoader). 
Since:1.6
/**
 * <code>ScriptEngineFactory</code> is used to describe and instantiate
 * <code>ScriptEngines</code>.
 * <br><br>
 * Each class implementing <code>ScriptEngine</code> has a corresponding
 * factory that exposes metadata describing the engine class.
 * <br><br>The <code>ScriptEngineManager</code>
 * uses the service-provider loader mechanism described in the
 * {@link java.util.ServiceLoader} class to obtain
 * instances of {@code ScriptEngineFactory} instances.
 * See {@link ScriptEngineManager#ScriptEngineManager()} and
 * {@link ScriptEngineManager#ScriptEngineManager(java.lang.ClassLoader)}.
 *
 * @since 1.6
 */
public interface ScriptEngineFactory {
    
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.
/**
     * Returns the full  name of the <code>ScriptEngine</code>.  For
     * instance an implementation based on the Mozilla Rhino Javascript engine
     * might return <i>Rhino Mozilla Javascript Engine</i>.
     * @return The name of the engine implementation.
     */
    public String getEngineName();

    
Returns the version of the ScriptEngine.

Returns:The ScriptEngine implementation version.
/**
     * Returns the version of the <code>ScriptEngine</code>.
     * @return The <code>ScriptEngine</code> implementation version.
     */
    public String getEngineVersion();


    
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.
/**
     * Returns an immutable list of filename extensions, which generally identify scripts
     * written in the language supported by this <code>ScriptEngine</code>.
     * The array is used by the <code>ScriptEngineManager</code> to implement its
     * <code>getEngineByExtension</code> method.
     * @return The list of extensions.
     */
    public List<String> getExtensions();


    
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.
/**
     * Returns an immutable list of mimetypes, associated with scripts that
     * can be executed by the engine.  The list is used by the
     * <code>ScriptEngineManager</code> class to implement its
     * <code>getEngineByMimetype</code> method.
     * @return The list of mime types.
     */
    public List<String> getMimeTypes();

    
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
/**
     * Returns an immutable list of  short names for the <code>ScriptEngine</code>, which may be used to
     * identify the <code>ScriptEngine</code> by the <code>ScriptEngineManager</code>.
     * For instance, an implementation based on the Mozilla Rhino Javascript engine might
     * return list containing {&quot;javascript&quot;, &quot;rhino&quot;}.
     * @return an immutable list of short names
     */
    public List<String> getNames();

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

Returns:The name of the supported language.
/**
     * Returns the name of the scripting language supported by this
     * <code>ScriptEngine</code>.
     * @return The name of the supported language.
     */
    public String getLanguageName();

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

Returns:The version of the supported language.
/**
     * Returns the version of the scripting language supported by this
     * <code>ScriptEngine</code>.
     * @return The version of the supported language.
     */
    public String getLanguageVersion();

    
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.

Params:
  • key – The name of the parameter
Throws:
Returns:The value for the given parameter. Returns null if no
value is assigned to the key.
/**
     * Returns the value of an attribute whose meaning may be implementation-specific.
     * Keys for which the value is defined in all implementations are:
     * <ul>
     * <li>ScriptEngine.ENGINE</li>
     * <li>ScriptEngine.ENGINE_VERSION</li>
     * <li>ScriptEngine.LANGUAGE</li>
     * <li>ScriptEngine.LANGUAGE_VERSION</li>
     * <li>ScriptEngine.NAME</li>
     * </ul>
     * <p>
     * The values for these keys are the Strings returned by <code>getEngineName</code>,
     * <code>getEngineVersion</code>, <code>getLanguageName</code>,
     * <code>getLanguageVersion</code> for the first four keys respectively. For NAME, one of the Strings
     * returned by <code>getNames</code> is returned.<br><br>
     * A reserved key, <code><b>THREADING</b></code>, 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 <code><b>THREADING</b></code> key are:<br><br>
     * <ul>
     * <li><code>null</code> - The engine implementation is not thread safe, and cannot
     * be used to execute scripts concurrently on multiple threads.
     * <li><code>&quot;MULTITHREADED&quot;</code> - 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.
     * <li><code>&quot;THREAD-ISOLATED&quot;</code> - The implementation satisfies the requirements
     * of &quot;MULTITHREADED&quot;, and also, the engine maintains independent values
     * for symbols in scripts executing on different threads.
     * <li><code>&quot;STATELESS&quot;</code> - The implementation satisfies the requirements of
     * <code>&quot;THREAD-ISOLATED&quot;</code>.  In addition, script executions do not alter the
     * mappings in the <code>Bindings</code> which is the engine scope of the
     * <code>ScriptEngine</code>.  In particular, the keys in the <code>Bindings</code>
     * and their associated values are the same before and after the execution of the script.
     * </ul>
     * <br><br>
     * Implementations may define implementation-specific keys.
     *
     * @param key The name of the parameter
     * @return The value for the given parameter. Returns <code>null</code> if no
     * value is assigned to the key.
     *
     * @throws NullPointerException if the key is null.
     */
    public Object getParameter(String key);

    
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;
 }
 


Params:
  • 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.
Throws:
Returns:The String used to invoke the method in the syntax of the scripting language.
/**
     * 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;
     *
     * <pre>{@code
     * 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;
     * }
     * } </pre>
     *
     * @param obj The name representing the object whose method is to be invoked. The
     * name is the one used to create bindings using the <code>put</code> method of
     * <code>ScriptEngine</code>, the <code>put</code> method of an <code>ENGINE_SCOPE</code>
     * <code>Bindings</code>,or the <code>setAttribute</code> method
     * of <code>ScriptContext</code>.  The identifier used in scripts may be a decorated form of the
     * specified one.
     *
     * @param m The name of the method to invoke.
     * @param args names of the arguments in the method call.
     *
     * @return 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.
     */
    public String getMethodCallSyntax(String obj, String m, String... args);

    
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 + ")";
}



Params:
  • 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.
/**
     * 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;
     *
     * <pre><code>
     * public String getOutputStatement(String toDisplay) {
     *      return "print(" + toDisplay + ")";
     * }
     * </code></pre>
     *
     * @param toDisplay The String to be displayed by the returned statement.
     * @return The string used to display the String in the syntax of the scripting language.
     *
     *
     */
    public String getOutputStatement(String toDisplay);


    
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 += "?>";
 }


 @param statements The statements to be executed.  May be return values of
 calls to the getMethodCallSyntax and getOutputStatement methods.
 @return The Program
 @throws NullPointerException if the statements array or any of its elements is null

/**
     * Returns a valid scripting language executable program with given statements.
     * For instance an implementation for a PHP engine might be:
     *
     * <pre>{@code
     * 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 += "?>";
     * }
     * }</pre>
     *
     *  @param statements The statements to be executed.  May be return values of
     *  calls to the <code>getMethodCallSyntax</code> and <code>getOutputStatement</code> methods.
     *  @return The Program
     *
     *  @throws NullPointerException if the <code>statements</code> array or any of its elements is null
     */
    public String getProgram(String... statements);

    
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.
/**
     * Returns an instance of the <code>ScriptEngine</code> associated with this
     * <code>ScriptEngineFactory</code>. A new ScriptEngine is generally
     * returned, but implementations may pool, share or reuse engines.
     *
     * @return A new <code>ScriptEngine</code> instance.
     */
    public  ScriptEngine getScriptEngine();
}