/*
* 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%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
* <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%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;
}
}
/**
* <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;
}