API Overview API Index Package Overview Direct link to this page
JDK 1.6
  javax.script. ScriptEngineManager View Javadoc
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441

/*
 * @(#)ScriptEngineManager.java	1.6 06/04/21 17:44:33
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTAIL. Use is subject to license terms.
 */

package javax.script;
import java.util.*;
import java.net.URL;
import java.io.*;
import java.security.*;
import sun.misc.Service;
import sun.misc.ServiceConfigurationError;
import sun.reflect.Reflection;
import sun.security.util.SecurityConstants;

/**
 * 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 an array 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;
    /**
     * If the thread context ClassLoader can be accessed by the caller, 
     * then the effect of calling this constructor is the same as calling 
     * <code>ScriptEngineManager(Thread.currentThread().getContextClassLoader())</code>.
     * Otherwise, the effect is the same as calling <code>ScriptEngineManager(null)</code>.
     *
     * @see java.lang.Thread#getContextClassLoader
     */
    public ScriptEngineManager() {
        ClassLoader ctxtLoader = Thread.currentThread().getContextClassLoader();
        if (canCallerAccessLoader(ctxtLoader)) {
            if (DEBUG) System.out.println("using " + ctxtLoader);
            init(ctxtLoader);
        } else {
            if (DEBUG) System.out.println("using bootstrap loader");
            init(null);
        }
    }
    
    /**
     * 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>();
        AccessController.doPrivileged(new PrivilegedAction() {
            public Object run() {
                initEngines(loader);
                return null;
            }
        });
    }

    private void initEngines(final ClassLoader loader) {
        Iterator itr = null;
        try {
            if (loader != null) {
                itr = Service.providers(ScriptEngineFactory.class, loader);
            } else {
                itr = Service.installedProviders(ScriptEngineFactory.class);
            }
        } 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 = (ScriptEngineFactory) 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;
        }
    }
    
    /**
     * <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;
    }
    
    /**
     * <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.
     * @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
     * @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 <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 array 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 <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 <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 an array 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 <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 <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 <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. */
    private HashSet<ScriptEngineFactory> engineSpis;
    
    /** Map of engine name to script engine factory. */
    private HashMap<String, ScriptEngineFactory> nameAssociations;
    
    /** Map of script file extension to script engine factory. */
    private HashMap<String, ScriptEngineFactory> extensionAssociations;
    
    /** 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. */
    private Bindings globalScope;
    
    private boolean canCallerAccessLoader(ClassLoader loader) {
        SecurityManager sm = System.getSecurityManager();
        if (sm != null) {
            ClassLoader callerLoader = getCallerClassLoader();
            if (callerLoader != null) {
                if (loader != callerLoader || !isAncestor(loader, callerLoader)) {
                    try {
                        sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
                    } catch (SecurityException exp) {
                        if (DEBUG) exp.printStackTrace();
                        return false;
                    }
                } // else fallthru..
            } // else fallthru..
        } // else fallthru..
        
        return true;
    }
    
    // Note that this code is same as ClassLoader.getCallerClassLoader().
    // But, that method is package private and hence we can't call here.
    private ClassLoader getCallerClassLoader() {
        Class caller = Reflection.getCallerClass(3);
        if (caller == null) {
            return null;
        }
        return caller.getClassLoader();
    }
    
    // is cl1 ancestor of cl2?
    private boolean isAncestor(ClassLoader cl1, ClassLoader cl2) {
        do {
            cl2 = cl2.getParent();
            if (cl1 == cl2) return true;
        } while (cl2 != null);
        return false;
    }
}

Generated By: JavaOnTracks Doclet 0.1.4     ©Thibaut Colar