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 * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package javax.script;
import java.util.*;
import java.security.*;
import java.util.ServiceLoader;
import java.util.ServiceConfigurationError;


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 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.

Author:Mike Grogan, A. Sundararajan
Since:1.6
/**
 * The <code>ScriptEngineManager</code> implements a discovery and instantiation
 * mechanism for <code>ScriptEngine</code> classes and also maintains a
 * collection of key/value pairs storing state shared by all engines created
 * by the Manager. This class uses the <a href="../../../technotes/guides/jar/jar.html#Service%20Provider">service provider</a> mechanism to enumerate all the
 * implementations of <code>ScriptEngineFactory</code>. <br><br>
 * The <code>ScriptEngineManager</code> 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.
 * <p>
 * The <code>Bindings</code> of key/value pairs, referred to as the "Global Scope"  maintained
 * by the manager is available to all instances of <code>ScriptEngine</code> created
 * by the <code>ScriptEngineManager</code>.  The values in the <code>Bindings</code> are
 * generally exposed in all scripts.
 *
 * @author Mike Grogan
 * @author A. Sundararajan
 * @since 1.6
 */
public class ScriptEngineManager  {
    private static final boolean DEBUG = false;
    
The effect of calling this constructor is the same as calling
ScriptEngineManager(Thread.currentThread().getContextClassLoader()).

See Also:
  • getContextClassLoader.getContextClassLoader
/**
     * The effect of calling this constructor is the same as calling
     * <code>ScriptEngineManager(Thread.currentThread().getContextClassLoader())</code>.
     *
     * @see java.lang.Thread#getContextClassLoader
     */
    public ScriptEngineManager() {
        ClassLoader ctxtLoader = Thread.currentThread().getContextClassLoader();
        init(ctxtLoader);
    }

    
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 and that are in the usual extension
directories (installed extensions) are loaded. 



Params:
  • loader – ClassLoader used to discover script engine factories.
/**
     * This constructor loads the implementations of
     * <code>ScriptEngineFactory</code> visible to the given
     * <code>ClassLoader</code> using the <a href="../../../technotes/guides/jar/jar.html#Service%20Provider">service provider</a> mechanism.<br><br>
     * If loader is <code>null</code>, the script engine factories that are
     * bundled with the platform and that are in the usual extension
     * directories (installed extensions) are loaded. <br><br>
     *
     * @param loader ClassLoader used to discover script engine factories.
     */
    public ScriptEngineManager(ClassLoader loader) {
        init(loader);
    }

    private void init(final ClassLoader loader) {
        globalScope = new SimpleBindings();
        engineSpis = new HashSet<ScriptEngineFactory>();
        nameAssociations = new HashMap<String, ScriptEngineFactory>();
        extensionAssociations = new HashMap<String, ScriptEngineFactory>();
        mimeTypeAssociations = new HashMap<String, ScriptEngineFactory>();
        initEngines(loader);
    }

    private ServiceLoader<ScriptEngineFactory> getServiceLoader(final ClassLoader loader) {
        if (loader != null) {
            return ServiceLoader.load(ScriptEngineFactory.class, loader);
        } else {
            return ServiceLoader.loadInstalled(ScriptEngineFactory.class);
        }
    }

    private void initEngines(final ClassLoader loader) {
        Iterator<ScriptEngineFactory> itr = null;
        try {
            ServiceLoader<ScriptEngineFactory> sl = AccessController.doPrivileged(
                new PrivilegedAction<ServiceLoader<ScriptEngineFactory>>() {
                    @Override
                    public ServiceLoader<ScriptEngineFactory> run() {
                        return getServiceLoader(loader);
                    }
                });

            itr = sl.iterator();
        } catch (ServiceConfigurationError err) {
            System.err.println("Can't find ScriptEngineFactory providers: " +
                          err.getMessage());
            if (DEBUG) {
                err.printStackTrace();
            }
            // do not throw any exception here. user may want to
            // manage his/her own factories using this manager
            // by explicit registratation (by registerXXX) methods.
            return;
        }

        try {
            while (itr.hasNext()) {
                try {
                    ScriptEngineFactory fact = itr.next();
                    engineSpis.add(fact);
                } catch (ServiceConfigurationError err) {
                    System.err.println("ScriptEngineManager providers.next(): "
                                 + err.getMessage());
                    if (DEBUG) {
                        err.printStackTrace();
                    }
                    // one factory failed, but check other factories...
                    continue;
                }
            }
        } catch (ServiceConfigurationError err) {
            System.err.println("ScriptEngineManager providers.hasNext(): "
                            + err.getMessage());
            if (DEBUG) {
                err.printStackTrace();
            }
            // do not throw any exception here. user may want to
            // manage his/her own factories using this manager
            // by explicit registratation (by registerXXX) methods.
            return;
        }
    }

    
setBindings stores the specified Bindings
in the globalScope field. ScriptEngineManager sets this
Bindings as global bindings for ScriptEngine
objects created by it.

Params:
  • bindings – The specified Bindings
Throws:
/**
     * <code>setBindings</code> stores the specified <code>Bindings</code>
     * in the <code>globalScope</code> field. ScriptEngineManager sets this
     * <code>Bindings</code> as global bindings for <code>ScriptEngine</code>
     * objects created by it.
     *
     * @param bindings The specified <code>Bindings</code>
     * @throws IllegalArgumentException if bindings is null.
     */
    public void setBindings(Bindings bindings) {
        if (bindings == null) {
            throw new IllegalArgumentException("Global scope cannot be null.");
        }

        globalScope = bindings;
    }

    
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.
/**
     * <code>getBindings</code> returns the value of the <code>globalScope</code> field.
     * ScriptEngineManager sets this <code>Bindings</code> as global bindings for
     * <code>ScriptEngine</code> objects created by it.
     *
     * @return The globalScope field.
     */
    public Bindings getBindings() {
        return globalScope;
    }

    
Sets the specified key/value pair in the Global Scope.

Params:
  • key – Key to set
  • value – Value to set.
Throws:
/**
     * Sets the specified key/value pair in the Global Scope.
     * @param key Key to set
     * @param value Value to set.
     * @throws NullPointerException if key is null.
     * @throws IllegalArgumentException if key is empty string.
     */
    public void put(String key, Object value) {
        globalScope.put(key, value);
    }

    
Gets the value for the specified key in the Global Scope

Params:
  • key – The key whose value is to be returned.
Returns:The value for the specified key.
/**
     * Gets the value for the specified key in the Global Scope
     * @param key The key whose value is to be returned.
     * @return The value for the specified key.
     */
    public Object get(String key) {
        return globalScope.get(key);
    }

    
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.

Params:
  • shortName – The short name of the ScriptEngine implementation.
returned by the getNames method of its ScriptEngineFactory.
Throws:
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.
/**
     * Looks up and creates a <code>ScriptEngine</code> for a given  name.
     * The algorithm first searches for a <code>ScriptEngineFactory</code> that has been
     * registered as a handler for the specified name using the <code>registerEngineName</code>
     * method.
     * <br><br> If one is not found, it searches the set of <code>ScriptEngineFactory</code> instances
     * stored by the constructor for one with the specified name.  If a <code>ScriptEngineFactory</code>
     * is found by either method, it is used to create instance of <code>ScriptEngine</code>.
     * @param shortName The short name of the <code>ScriptEngine</code> implementation.
     * returned by the <code>getNames</code> method of its <code>ScriptEngineFactory</code>.
     * @return A <code>ScriptEngine</code> created by the factory located in the search.  Returns null
     * if no such factory was found.  The <code>ScriptEngineManager</code> sets its own <code>globalScope</code>
     * <code>Bindings</code> as the <code>GLOBAL_SCOPE</code> <code>Bindings</code> of the newly
     * created <code>ScriptEngine</code>.
     * @throws NullPointerException if shortName is null.
     */
    public ScriptEngine getEngineByName(String shortName) {
        if (shortName == null) throw new NullPointerException();
        //look for registered name first
        Object obj;
        if (null != (obj = nameAssociations.get(shortName))) {
            ScriptEngineFactory spi = (ScriptEngineFactory)obj;
            try {
                ScriptEngine engine = spi.getScriptEngine();
                engine.setBindings(getBindings(), ScriptContext.GLOBAL_SCOPE);
                return engine;
            } catch (Exception exp) {
                if (DEBUG) exp.printStackTrace();
            }
        }

        for (ScriptEngineFactory spi : engineSpis) {
            List<String> names = null;
            try {
                names = spi.getNames();
            } catch (Exception exp) {
                if (DEBUG) exp.printStackTrace();
            }

            if (names != null) {
                for (String name : names) {
                    if (shortName.equals(name)) {
                        try {
                            ScriptEngine engine = spi.getScriptEngine();
                            engine.setBindings(getBindings(), ScriptContext.GLOBAL_SCOPE);
                            return engine;
                        } catch (Exception exp) {
                            if (DEBUG) exp.printStackTrace();
                        }
                    }
                }
            }
        }

        return null;
    }

    
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.

Params:
  • extension – The given extension
Throws:
Returns:The engine to handle scripts with this extension.  Returns null
if not found.
/**
     * Look up and create a <code>ScriptEngine</code> for a given extension.  The algorithm
     * used by <code>getEngineByName</code> is used except that the search starts
     * by looking for a <code>ScriptEngineFactory</code> registered to handle the
     * given extension using <code>registerEngineExtension</code>.
     * @param extension The given extension
     * @return The engine to handle scripts with this extension.  Returns <code>null</code>
     * if not found.
     * @throws NullPointerException if extension is null.
     */
    public ScriptEngine getEngineByExtension(String extension) {
        if (extension == null) throw new NullPointerException();
        //look for registered extension first
        Object obj;
        if (null != (obj = extensionAssociations.get(extension))) {
            ScriptEngineFactory spi = (ScriptEngineFactory)obj;
            try {
                ScriptEngine engine = spi.getScriptEngine();
                engine.setBindings(getBindings(), ScriptContext.GLOBAL_SCOPE);
                return engine;
            } catch (Exception exp) {
                if (DEBUG) exp.printStackTrace();
            }
        }

        for (ScriptEngineFactory spi : engineSpis) {
            List<String> exts = null;
            try {
                exts = spi.getExtensions();
            } catch (Exception exp) {
                if (DEBUG) exp.printStackTrace();
            }
            if (exts == null) continue;
            for (String ext : exts) {
                if (extension.equals(ext)) {
                    try {
                        ScriptEngine engine = spi.getScriptEngine();
                        engine.setBindings(getBindings(), ScriptContext.GLOBAL_SCOPE);
                        return engine;
                    } catch (Exception exp) {
                        if (DEBUG) exp.printStackTrace();
                    }
                }
            }
        }
        return null;
    }

    
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.

Params:
  • mimeType – The given mime type
Throws:
Returns:The engine to handle scripts with this mime type.  Returns null
if not found.
/**
     * Look up and create a <code>ScriptEngine</code> for a given mime type.  The algorithm
     * used by <code>getEngineByName</code> is used except that the search starts
     * by looking for a <code>ScriptEngineFactory</code> registered to handle the
     * given mime type using <code>registerEngineMimeType</code>.
     * @param mimeType The given mime type
     * @return The engine to handle scripts with this mime type.  Returns <code>null</code>
     * if not found.
     * @throws NullPointerException if mimeType is null.
     */
    public ScriptEngine getEngineByMimeType(String mimeType) {
        if (mimeType == null) throw new NullPointerException();
        //look for registered types first
        Object obj;
        if (null != (obj = mimeTypeAssociations.get(mimeType))) {
            ScriptEngineFactory spi = (ScriptEngineFactory)obj;
            try {
                ScriptEngine engine = spi.getScriptEngine();
                engine.setBindings(getBindings(), ScriptContext.GLOBAL_SCOPE);
                return engine;
            } catch (Exception exp) {
                if (DEBUG) exp.printStackTrace();
            }
        }

        for (ScriptEngineFactory spi : engineSpis) {
            List<String> types = null;
            try {
                types = spi.getMimeTypes();
            } catch (Exception exp) {
                if (DEBUG) exp.printStackTrace();
            }
            if (types == null) continue;
            for (String type : types) {
                if (mimeType.equals(type)) {
                    try {
                        ScriptEngine engine = spi.getScriptEngine();
                        engine.setBindings(getBindings(), ScriptContext.GLOBAL_SCOPE);
                        return engine;
                    } catch (Exception exp) {
                        if (DEBUG) exp.printStackTrace();
                    }
                }
            }
        }
        return null;
    }

    
Returns a list whose elements are instances of all the ScriptEngineFactory classes
found by the discovery mechanism.

Returns:List of all discovered ScriptEngineFactorys.
/**
     * Returns a list whose elements are instances of all the <code>ScriptEngineFactory</code> classes
     * found by the discovery mechanism.
     * @return List of all discovered <code>ScriptEngineFactory</code>s.
     */
    public List<ScriptEngineFactory> getEngineFactories() {
        List<ScriptEngineFactory> res = new ArrayList<ScriptEngineFactory>(engineSpis.size());
        for (ScriptEngineFactory spi : engineSpis) {
            res.add(spi);
        }
        return Collections.unmodifiableList(res);
    }

    
Registers a ScriptEngineFactory to handle a language
name.  Overrides any such association found using the Discovery mechanism.

Params:
  • name – The name to be associated with the ScriptEngineFactory.
  • factory – The class to associate with the given name.
Throws:
/**
     * Registers a <code>ScriptEngineFactory</code> to handle a language
     * name.  Overrides any such association found using the Discovery mechanism.
     * @param name The name to be associated with the <code>ScriptEngineFactory</code>.
     * @param factory The class to associate with the given name.
     * @throws NullPointerException if any of the parameters is null.
     */
    public void registerEngineName(String name, ScriptEngineFactory factory) {
        if (name == null || factory == null) throw new NullPointerException();
        nameAssociations.put(name, factory);
    }

    
Registers a ScriptEngineFactory to handle a mime type.
Overrides any such association found using the Discovery mechanism.

Params:
  • type – The mime type  to be associated with the
ScriptEngineFactory.
  • factory – The class to associate with the given mime type.
Throws:
/**
     * Registers a <code>ScriptEngineFactory</code> to handle a mime type.
     * Overrides any such association found using the Discovery mechanism.
     *
     * @param type The mime type  to be associated with the
     * <code>ScriptEngineFactory</code>.
     *
     * @param factory The class to associate with the given mime type.
     * @throws NullPointerException if any of the parameters is null.
     */
    public void registerEngineMimeType(String type, ScriptEngineFactory factory) {
        if (type == null || factory == null) throw new NullPointerException();
        mimeTypeAssociations.put(type, factory);
    }

    
Registers a ScriptEngineFactory to handle an extension.
Overrides any such association found using the Discovery mechanism.

Params:
  • extension – The extension type  to be associated with the
ScriptEngineFactory.
  • factory – The class to associate with the given extension.
Throws:
/**
     * Registers a <code>ScriptEngineFactory</code> to handle an extension.
     * Overrides any such association found using the Discovery mechanism.
     *
     * @param extension The extension type  to be associated with the
     * <code>ScriptEngineFactory</code>.
     * @param factory The class to associate with the given extension.
     * @throws NullPointerException if any of the parameters is null.
     */
    public void registerEngineExtension(String extension, ScriptEngineFactory factory) {
        if (extension == null || factory == null) throw new NullPointerException();
        extensionAssociations.put(extension, factory);
    }

    
Set of script engine factories discovered. 
/** Set of script engine factories discovered. */
    private HashSet<ScriptEngineFactory> engineSpis;

    
Map of engine name to script engine factory. 
/** Map of engine name to script engine factory. */
    private HashMap<String, ScriptEngineFactory> nameAssociations;

    
Map of script file extension to script engine factory. 
/** Map of script file extension to script engine factory. */
    private HashMap<String, ScriptEngineFactory> extensionAssociations;

    
Map of script script MIME type to script engine factory. 
/** Map of script script MIME type to script engine factory. */
    private HashMap<String, ScriptEngineFactory> mimeTypeAssociations;

    
Global bindings associated with script engines created by this manager. 
/** Global bindings associated with script engines created by this manager. */
    private Bindings globalScope;
}