1 /*
2 * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package javax.script;
27 import java.util.*;
28 import java.security.*;
29 import java.util.ServiceLoader;
30 import java.util.ServiceConfigurationError;
31
32 /**
33 * The <code>ScriptEngineManager</code> implements a discovery and instantiation
34 * mechanism for <code>ScriptEngine</code> classes and also maintains a
35 * collection of key/value pairs storing state shared by all engines created
36 * by the Manager. This class uses the <a href="../../../technotes/guides/jar/jar.html#Service%20Provider">service provider</a> mechanism to enumerate all the
37 * implementations of <code>ScriptEngineFactory</code>. <br><br>
38 * The <code>ScriptEngineManager</code> provides a method to return a list of all these factories
39 * as well as utility methods which look up factories on the basis of language name, file extension
40 * and mime type.
41 * <p>
42 * The <code>Bindings</code> of key/value pairs, referred to as the "Global Scope" maintained
43 * by the manager is available to all instances of <code>ScriptEngine</code> created
44 * by the <code>ScriptEngineManager</code>. The values in the <code>Bindings</code> are
45 * generally exposed in all scripts.
46 *
47 * @author Mike Grogan
48 * @author A. Sundararajan
49 * @since 1.6
50 */
51 public class ScriptEngineManager {
52 private static final boolean DEBUG = false;
53 /**
54 * The effect of calling this constructor is the same as calling
55 * <code>ScriptEngineManager(Thread.currentThread().getContextClassLoader())</code>.
56 *
57 * @see java.lang.Thread#getContextClassLoader
58 */
59 public ScriptEngineManager() {
60 ClassLoader ctxtLoader = Thread.currentThread().getContextClassLoader();
61 init(ctxtLoader);
62 }
63
64 /**
65 * This constructor loads the implementations of
66 * <code>ScriptEngineFactory</code> visible to the given
67 * <code>ClassLoader</code> using the <a href="../../../technotes/guides/jar/jar.html#Service%20Provider">service provider</a> mechanism.<br><br>
68 * If loader is <code>null</code>, the script engine factories that are
69 * bundled with the platform are loaded. <br>
70 *
71 * @param loader ClassLoader used to discover script engine factories.
72 */
73 public ScriptEngineManager(ClassLoader loader) {
74 init(loader);
75 }
76
77 private void init(final ClassLoader loader) {
78 globalScope = new SimpleBindings();
79 engineSpis = new HashSet<ScriptEngineFactory>();
80 nameAssociations = new HashMap<String, ScriptEngineFactory>();
81 extensionAssociations = new HashMap<String, ScriptEngineFactory>();
82 mimeTypeAssociations = new HashMap<String, ScriptEngineFactory>();
83 initEngines(loader);
84 }
85
86 private ServiceLoader<ScriptEngineFactory> getServiceLoader(final ClassLoader loader) {
87 if (loader != null) {
88 return ServiceLoader.load(ScriptEngineFactory.class, loader);
89 } else {
90 return ServiceLoader.loadInstalled(ScriptEngineFactory.class);
91 }
92 }
93
94 private void initEngines(final ClassLoader loader) {
95 Iterator<ScriptEngineFactory> itr = null;
96 try {
97 ServiceLoader<ScriptEngineFactory> sl = AccessController.doPrivileged(
98 new PrivilegedAction<ServiceLoader<ScriptEngineFactory>>() {
99 @Override
100 public ServiceLoader<ScriptEngineFactory> run() {
101 return getServiceLoader(loader);
102 }
103 });
104
105 itr = sl.iterator();
106 } catch (ServiceConfigurationError err) {
107 System.err.println("Can't find ScriptEngineFactory providers: " +
108 err.getMessage());
109 if (DEBUG) {
110 err.printStackTrace();
111 }
112 // do not throw any exception here. user may want to
113 // manage his/her own factories using this manager
114 // by explicit registratation (by registerXXX) methods.
115 return;
116 }
117
118 try {
119 while (itr.hasNext()) {
120 try {
121 ScriptEngineFactory fact = itr.next();
122 engineSpis.add(fact);
123 } catch (ServiceConfigurationError err) {
124 System.err.println("ScriptEngineManager providers.next(): "
125 + err.getMessage());
126 if (DEBUG) {
127 err.printStackTrace();
128 }
129 // one factory failed, but check other factories...
130 continue;
131 }
132 }
133 } catch (ServiceConfigurationError err) {
134 System.err.println("ScriptEngineManager providers.hasNext(): "
135 + err.getMessage());
136 if (DEBUG) {
137 err.printStackTrace();
138 }
139 // do not throw any exception here. user may want to
140 // manage his/her own factories using this manager
141 // by explicit registratation (by registerXXX) methods.
142 return;
143 }
144 }
145
146 /**
147 * <code>setBindings</code> stores the specified <code>Bindings</code>
148 * in the <code>globalScope</code> field. ScriptEngineManager sets this
149 * <code>Bindings</code> as global bindings for <code>ScriptEngine</code>
150 * objects created by it.
151 *
152 * @param bindings The specified <code>Bindings</code>
153 * @throws IllegalArgumentException if bindings is null.
154 */
155 public void setBindings(Bindings bindings) {
156 if (bindings == null) {
157 throw new IllegalArgumentException("Global scope cannot be null.");
158 }
159
160 globalScope = bindings;
161 }
162
163 /**
164 * <code>getBindings</code> returns the value of the <code>globalScope</code> field.
165 * ScriptEngineManager sets this <code>Bindings</code> as global bindings for
166 * <code>ScriptEngine</code> objects created by it.
167 *
168 * @return The globalScope field.
169 */
170 public Bindings getBindings() {
171 return globalScope;
172 }
173
174 /**
175 * Sets the specified key/value pair in the Global Scope.
176 * @param key Key to set
177 * @param value Value to set.
178 * @throws NullPointerException if key is null.
179 * @throws IllegalArgumentException if key is empty string.
180 */
181 public void put(String key, Object value) {
182 globalScope.put(key, value);
183 }
184
185 /**
186 * Gets the value for the specified key in the Global Scope
187 * @param key The key whose value is to be returned.
188 * @return The value for the specified key.
189 */
190 public Object get(String key) {
191 return globalScope.get(key);
192 }
193
194 /**
195 * Looks up and creates a <code>ScriptEngine</code> for a given name.
196 * The algorithm first searches for a <code>ScriptEngineFactory</code> that has been
197 * registered as a handler for the specified name using the <code>registerEngineName</code>
198 * method.
199 * <br><br> If one is not found, it searches the set of <code>ScriptEngineFactory</code> instances
200 * stored by the constructor for one with the specified name. If a <code>ScriptEngineFactory</code>
201 * is found by either method, it is used to create instance of <code>ScriptEngine</code>.
202 * @param shortName The short name of the <code>ScriptEngine</code> implementation.
203 * returned by the <code>getNames</code> method of its <code>ScriptEngineFactory</code>.
204 * @return A <code>ScriptEngine</code> created by the factory located in the search. Returns null
205 * if no such factory was found. The <code>ScriptEngineManager</code> sets its own <code>globalScope</code>
206 * <code>Bindings</code> as the <code>GLOBAL_SCOPE</code> <code>Bindings</code> of the newly
207 * created <code>ScriptEngine</code>.
208 * @throws NullPointerException if shortName is null.
209 */
210 public ScriptEngine getEngineByName(String shortName) {
211 if (shortName == null) throw new NullPointerException();
212 //look for registered name first
213 Object obj;
214 if (null != (obj = nameAssociations.get(shortName))) {
215 ScriptEngineFactory spi = (ScriptEngineFactory)obj;
216 try {
217 ScriptEngine engine = spi.getScriptEngine();
218 engine.setBindings(getBindings(), ScriptContext.GLOBAL_SCOPE);
219 return engine;
220 } catch (Exception exp) {
221 if (DEBUG) exp.printStackTrace();
222 }
223 }
224
225 for (ScriptEngineFactory spi : engineSpis) {
226 List<String> names = null;
227 try {
228 names = spi.getNames();
229 } catch (Exception exp) {
230 if (DEBUG) exp.printStackTrace();
231 }
232
233 if (names != null) {
234 for (String name : names) {
235 if (shortName.equals(name)) {
236 try {
237 ScriptEngine engine = spi.getScriptEngine();
238 engine.setBindings(getBindings(), ScriptContext.GLOBAL_SCOPE);
239 return engine;
240 } catch (Exception exp) {
241 if (DEBUG) exp.printStackTrace();
242 }
243 }
244 }
245 }
246 }
247
248 return null;
249 }
250
251 /**
252 * Look up and create a <code>ScriptEngine</code> for a given extension. The algorithm
253 * used by <code>getEngineByName</code> is used except that the search starts
254 * by looking for a <code>ScriptEngineFactory</code> registered to handle the
255 * given extension using <code>registerEngineExtension</code>.
256 * @param extension The given extension
257 * @return The engine to handle scripts with this extension. Returns <code>null</code>
258 * if not found.
259 * @throws NullPointerException if extension is null.
260 */
261 public ScriptEngine getEngineByExtension(String extension) {
262 if (extension == null) throw new NullPointerException();
263 //look for registered extension first
264 Object obj;
265 if (null != (obj = extensionAssociations.get(extension))) {
266 ScriptEngineFactory spi = (ScriptEngineFactory)obj;
267 try {
268 ScriptEngine engine = spi.getScriptEngine();
269 engine.setBindings(getBindings(), ScriptContext.GLOBAL_SCOPE);
270 return engine;
271 } catch (Exception exp) {
272 if (DEBUG) exp.printStackTrace();
273 }
274 }
275
276 for (ScriptEngineFactory spi : engineSpis) {
277 List<String> exts = null;
278 try {
279 exts = spi.getExtensions();
280 } catch (Exception exp) {
281 if (DEBUG) exp.printStackTrace();
282 }
283 if (exts == null) continue;
284 for (String ext : exts) {
285 if (extension.equals(ext)) {
286 try {
287 ScriptEngine engine = spi.getScriptEngine();
288 engine.setBindings(getBindings(), ScriptContext.GLOBAL_SCOPE);
289 return engine;
290 } catch (Exception exp) {
291 if (DEBUG) exp.printStackTrace();
292 }
293 }
294 }
295 }
296 return null;
297 }
298
299 /**
300 * Look up and create a <code>ScriptEngine</code> for a given mime type. The algorithm
301 * used by <code>getEngineByName</code> is used except that the search starts
302 * by looking for a <code>ScriptEngineFactory</code> registered to handle the
303 * given mime type using <code>registerEngineMimeType</code>.
304 * @param mimeType The given mime type
305 * @return The engine to handle scripts with this mime type. Returns <code>null</code>
306 * if not found.
307 * @throws NullPointerException if mimeType is null.
308 */
309 public ScriptEngine getEngineByMimeType(String mimeType) {
310 if (mimeType == null) throw new NullPointerException();
311 //look for registered types first
312 Object obj;
313 if (null != (obj = mimeTypeAssociations.get(mimeType))) {
314 ScriptEngineFactory spi = (ScriptEngineFactory)obj;
315 try {
316 ScriptEngine engine = spi.getScriptEngine();
317 engine.setBindings(getBindings(), ScriptContext.GLOBAL_SCOPE);
318 return engine;
319 } catch (Exception exp) {
320 if (DEBUG) exp.printStackTrace();
321 }
322 }
323
324 for (ScriptEngineFactory spi : engineSpis) {
325 List<String> types = null;
326 try {
327 types = spi.getMimeTypes();
328 } catch (Exception exp) {
329 if (DEBUG) exp.printStackTrace();
330 }
331 if (types == null) continue;
332 for (String type : types) {
333 if (mimeType.equals(type)) {
334 try {
335 ScriptEngine engine = spi.getScriptEngine();
336 engine.setBindings(getBindings(), ScriptContext.GLOBAL_SCOPE);
337 return engine;
338 } catch (Exception exp) {
339 if (DEBUG) exp.printStackTrace();
340 }
341 }
342 }
343 }
344 return null;
345 }
346
347 /**
348 * Returns a list whose elements are instances of all the <code>ScriptEngineFactory</code> classes
349 * found by the discovery mechanism.
350 * @return List of all discovered <code>ScriptEngineFactory</code>s.
351 */
352 public List<ScriptEngineFactory> getEngineFactories() {
353 List<ScriptEngineFactory> res = new ArrayList<ScriptEngineFactory>(engineSpis.size());
354 for (ScriptEngineFactory spi : engineSpis) {
355 res.add(spi);
356 }
357 return Collections.unmodifiableList(res);
358 }
359
360 /**
361 * Registers a <code>ScriptEngineFactory</code> to handle a language
362 * name. Overrides any such association found using the Discovery mechanism.
363 * @param name The name to be associated with the <code>ScriptEngineFactory</code>.
364 * @param factory The class to associate with the given name.
365 * @throws NullPointerException if any of the parameters is null.
366 */
367 public void registerEngineName(String name, ScriptEngineFactory factory) {
368 if (name == null || factory == null) throw new NullPointerException();
369 nameAssociations.put(name, factory);
370 }
371
372 /**
373 * Registers a <code>ScriptEngineFactory</code> to handle a mime type.
374 * Overrides any such association found using the Discovery mechanism.
375 *
376 * @param type The mime type to be associated with the
377 * <code>ScriptEngineFactory</code>.
378 *
379 * @param factory The class to associate with the given mime type.
380 * @throws NullPointerException if any of the parameters is null.
381 */
382 public void registerEngineMimeType(String type, ScriptEngineFactory factory) {
383 if (type == null || factory == null) throw new NullPointerException();
384 mimeTypeAssociations.put(type, factory);
385 }
386
387 /**
388 * Registers a <code>ScriptEngineFactory</code> to handle an extension.
389 * Overrides any such association found using the Discovery mechanism.
390 *
391 * @param extension The extension type to be associated with the
392 * <code>ScriptEngineFactory</code>.
393 * @param factory The class to associate with the given extension.
394 * @throws NullPointerException if any of the parameters is null.
395 */
396 public void registerEngineExtension(String extension, ScriptEngineFactory factory) {
397 if (extension == null || factory == null) throw new NullPointerException();
398 extensionAssociations.put(extension, factory);
399 }
400
401 /** Set of script engine factories discovered. */
402 private HashSet<ScriptEngineFactory> engineSpis;
403
404 /** Map of engine name to script engine factory. */
405 private HashMap<String, ScriptEngineFactory> nameAssociations;
406
407 /** Map of script file extension to script engine factory. */
408 private HashMap<String, ScriptEngineFactory> extensionAssociations;
409
410 /** Map of script script MIME type to script engine factory. */
411 private HashMap<String, ScriptEngineFactory> mimeTypeAssociations;
412
413 /** Global bindings associated with script engines created by this manager. */
414 private Bindings globalScope;
415 }