JDK14/Java14源码在线阅读
/*
* Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* 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
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
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 service provider mechanism described in the
* {@link java.util.ServiceLoader} class 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 service provider mechanism.<br><br>
* If loader is <code>null</code>, the script engine factories that are
* bundled with the platform are loaded. <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 TreeSet<ScriptEngineFactory>(Comparator.comparing(
ScriptEngineFactory::getEngineName,
Comparator.nullsLast(Comparator.naturalOrder()))
);
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.
*
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