- /*
- * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
- * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
- *
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- *
- */
- package javax.script;
- import java.util.*;
- import java.security.*;
- import java.util.ServiceLoader;
- import java.util.ServiceConfigurationError;
- /**
- * 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 Provider">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
- * <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
- * <code>ScriptEngineFactory</code> visible to the given
- * <code>ClassLoader</code> using the <a href="../../../technotes/guides/jar/jar.html#Service Provider">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;
- }
- }
- /**
- * <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 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 <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 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 <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;
- }
来源: https://www.cnblogs.com/shirui/p/9402272.html