org.apache.tinkerpop.gremlin.jsr223.DefaultGremlinScriptEngineManager Maven / Gradle / Ivy
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package org.apache.tinkerpop.gremlin.jsr223;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.script.Bindings;
import javax.script.ScriptContext;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.ServiceConfigurationError;
import java.util.ServiceLoader;
import java.util.stream.Collectors;
import java.util.stream.Stream;
/**
* The {@code ScriptEngineManager} implements a discovery, instantiation and configuration mechanism for
* {@link GremlinScriptEngine} classes and also maintains a collection of key/value pairs storing state shared by all
* engines created by it. This class uses the {@code ServiceProvider} mechanism to enumerate all the
* implementations of GremlinScriptEngineFactory. The ScriptEngineManager 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.
*
* The {@code Bindings} of key/value pairs, referred to as the "Global Scope" maintained by the manager is available
* to all instances of @code ScriptEngine} created by the {@code GremlinScriptEngineManager}. The values
* in the {@code Bindings} are generally exposed in all scripts.
*
* This class is based quite heavily on the workings of the {@code ScriptEngineManager} supplied in the
* {@code javax.script} packages, but adds some additional features that are specific to Gremlin and TinkerPop.
* Unfortunately, it's not easily possible to extend {@code ScriptEngineManager} directly as there certain behaviors
* don't appear to be be straightforward to implement and member variables are all private. It is important to note
* that this class is designed to provide support for "Gremlin-enabled" {@code ScriptEngine} instances (i.e. those
* that extend from {@link GremlinScriptEngine}) and is not meant to manage just any {@code ScriptEngine} instance
* that may be on the path.
*
* As this is a "Gremlin" {@code ScriptEngine}, certain common imports are automatically applied when a
* {@link GremlinScriptEngine} is instantiated via the {@link GremlinScriptEngineFactory}.. Initial imports from
* gremlin-core come from the {@link CoreImports}.
*
* @author Stephen Mallette (http://stephen.genoprime.com)
*/
public class DefaultGremlinScriptEngineManager implements GremlinScriptEngineManager {
private static final Logger logger = LoggerFactory.getLogger(DefaultGremlinScriptEngineManager.class);
/**
* Set of script engine factories discovered.
*/
private final HashSet engineSpis = new HashSet<>();
/**
* Map of engine name to script engine factory.
*/
private final HashMap nameAssociations = new HashMap<>();
/**
* Map of script file extension to script engine factory.
*/
private final HashMap extensionAssociations = new HashMap<>();
/**
* Map of script script MIME type to script engine factory.
*/
private final HashMap mimeTypeAssociations = new HashMap<>();
/**
* Global bindings associated with script engines created by this manager.
*/
private Bindings globalScope = new ConcurrentBindings();
/**
* List of extensions for the {@link GremlinScriptEngineManager} which will be used to supply
* {@link Customizer} instances to {@link GremlinScriptEngineFactory} that are instantiated.
*/
private List plugins = new ArrayList<>();
/**
* The effect of calling this constructor is the same as calling
* {@code DefaultGremlinScriptEngineManager(Thread.currentThread().getContextClassLoader())}.
*/
public DefaultGremlinScriptEngineManager() {
final ClassLoader ctxtLoader = Thread.currentThread().getContextClassLoader();
initEngines(ctxtLoader);
}
/**
* This constructor loads the implementations of {@link GremlinScriptEngineFactory} visible to the given
* {@code ClassLoader} using the {@code ServiceLoader} mechanism. If loader is null, the script
* engine factories that are bundled with the platform and that are in the usual extension directories
* (installed extensions) are loaded.
*/
public DefaultGremlinScriptEngineManager(final ClassLoader loader) {
initEngines(loader);
}
@Override
public List getCustomizers(final String scriptEngineName) {
final List pluginCustomizers = plugins.stream().flatMap(plugin -> {
final Optional customizers = plugin.getCustomizers(scriptEngineName);
return Stream.of(customizers.orElse(new Customizer[0]));
}).collect(Collectors.toList());
return pluginCustomizers;
}
@Override
public void addPlugin(final GremlinPlugin plugin) {
// TODO: should modules be a set based on "name" to ensure uniqueness? not sure what bad stuff can happen with dupes
if (plugin != null) plugins.add(plugin);
}
/**
* Stores the specified {@code Bindings} as a global for all {@link GremlinScriptEngine} objects created by it.
* If the bindings are to be updated by multiple threads it is recommended that a {@link ConcurrentBindings}
* instance is supplied.
*
* @throws IllegalArgumentException if bindings is null.
*/
@Override
public synchronized void setBindings(final Bindings bindings) {
if (null == bindings) throw new IllegalArgumentException("Global scope cannot be null.");
globalScope = bindings;
}
/**
* Gets the bindings of the {@code Bindings} in global scope.
*/
@Override
public Bindings getBindings() {
return globalScope;
}
/**
* Sets the specified key/value pair in the global scope. The key may not be null or empty.
*
* @throws IllegalArgumentException if key is null or empty.
*/
@Override
public void put(final String key, final Object value) {
if (null == key) throw new IllegalArgumentException("key may not be null");
if (key.isEmpty()) throw new IllegalArgumentException("key may not be empty");
globalScope.put(key, value);
}
/**
* Gets the value for the specified key in the global scope.
*/
@Override
public Object get(final String key) {
return globalScope.get(key);
}
/**
* Looks up and creates a {@link GremlinScriptEngine} for a given name. The algorithm first searches for a
* {@link GremlinScriptEngineFactory} that has been registered as a handler for the specified name using the
* {@link #registerEngineExtension(String, GremlinScriptEngineFactory)} method. If one is not found, it searches
* the set of {@code GremlinScriptEngineFactory} instances stored by the constructor for one with the specified
* name. If a {@code ScriptEngineFactory} is found by either method, it is used to create instance of
* {@link GremlinScriptEngine}.
*
* @param shortName The short name of the {@link GremlinScriptEngine} implementation returned by the
* {@link GremlinScriptEngineFactory#getNames} method.
* @return A {@link GremlinScriptEngine} created by the factory located in the search. Returns {@code null}
* if no such factory was found. The global scope of this manager is applied to the newly created
* {@link GremlinScriptEngine}
* @throws NullPointerException if shortName is {@code null}.
*/
@Override
public GremlinScriptEngine getEngineByName(final String shortName) {
if (null == shortName) throw new NullPointerException();
//look for registered name first
Object obj;
if (null != (obj = nameAssociations.get(shortName))) {
final GremlinScriptEngineFactory spi = (GremlinScriptEngineFactory) obj;
try {
return createGremlinScriptEngine(spi);
} catch (Exception exp) {
logger.error(String.format("Could not create GremlinScriptEngine for %s", shortName), exp);
}
}
for (GremlinScriptEngineFactory spi : engineSpis) {
List names = null;
try {
names = spi.getNames();
} catch (Exception exp) {
logger.error("Could not get GremlinScriptEngine names", exp);
}
if (names != null) {
for (String name : names) {
if (shortName.equals(name)) {
try {
return createGremlinScriptEngine(spi);
} catch (Exception exp) {
logger.error(String.format("Could not create GremlinScriptEngine for %s", shortName), exp);
}
}
}
}
}
return null;
}
/**
* Look up and create a {@link GremlinScriptEngine} for a given extension. The algorithm
* used by {@link #getEngineByName(String)} is used except that the search starts by looking for a
* {@link GremlinScriptEngineFactory} registered to handle the given extension using
* {@link #registerEngineExtension(String, GremlinScriptEngineFactory)}.
*
* @return The engine to handle scripts with this extension. Returns {@code null} if not found.
* @throws NullPointerException if extension is {@code null}.
*/
@Override
public GremlinScriptEngine getEngineByExtension(final String extension) {
if (null == extension) throw new NullPointerException();
//look for registered extension first
Object obj;
if (null != (obj = extensionAssociations.get(extension))) {
final GremlinScriptEngineFactory spi = (GremlinScriptEngineFactory) obj;
try {
return createGremlinScriptEngine(spi);
} catch (Exception exp) {
logger.error(String.format("Could not create GremlinScriptEngine for %s", extension), exp);
}
}
for (GremlinScriptEngineFactory spi : engineSpis) {
List exts = null;
try {
exts = spi.getExtensions();
} catch (Exception exp) {
logger.error("Could not get GremlinScriptEngine extensions", exp);
}
if (exts == null) continue;
for (String ext : exts) {
if (extension.equals(ext)) {
try {
return createGremlinScriptEngine(spi);
} catch (Exception exp) {
logger.error(String.format("Could not create GremlinScriptEngine for %s", extension), exp);
}
}
}
}
return null;
}
/**
* Look up and create a {@link GremlinScriptEngine} for a given mime type. The algorithm used by
* {@link #getEngineByName(String)} is used except that the search starts by looking for a
* {@link GremlinScriptEngineFactory} registered to handle the given mime type using
* {@link #registerEngineMimeType(String, GremlinScriptEngineFactory)}.
*
* @param mimeType The given mime type
* @return The engine to handle scripts with this mime type. Returns {@code null} if not found.
* @throws NullPointerException if mime-type is {@code null}.
*/
@Override
public GremlinScriptEngine getEngineByMimeType(final String mimeType) {
if (null == mimeType) throw new NullPointerException();
//look for registered types first
Object obj;
if (null != (obj = mimeTypeAssociations.get(mimeType))) {
final GremlinScriptEngineFactory spi = (GremlinScriptEngineFactory) obj;
try {
return createGremlinScriptEngine(spi);
} catch (Exception exp) {
logger.error(String.format("Could not create GremlinScriptEngine for %s", mimeType), exp);
}
}
for (GremlinScriptEngineFactory spi : engineSpis) {
List types = null;
try {
types = spi.getMimeTypes();
} catch (Exception exp) {
logger.error("Could not get GremlinScriptEngine mimetypes", exp);
}
if (types == null) continue;
for (String type : types) {
if (mimeType.equals(type)) {
try {
return createGremlinScriptEngine(spi);
} catch (Exception exp) {
logger.error(String.format("Could not create GremlinScriptEngine for %s", mimeType), exp);
}
}
}
}
return null;
}
/**
* Returns a list whose elements are instances of all the {@link GremlinScriptEngineFactory} classes
* found by the discovery mechanism.
*
* @return List of all discovered {@link GremlinScriptEngineFactory} objects.
*/
@Override
public List getEngineFactories() {
final List res = new ArrayList<>(engineSpis.size());
res.addAll(engineSpis.stream().collect(Collectors.toList()));
return Collections.unmodifiableList(res);
}
/**
* Registers a {@link GremlinScriptEngineFactory} to handle a language name. Overrides any such association found
* using the discovery mechanism.
*
* @param name The name to be associated with the {@link GremlinScriptEngineFactory}
* @param factory The class to associate with the given name.
* @throws NullPointerException if any of the parameters is null.
*/
@Override
public void registerEngineName(final String name, final GremlinScriptEngineFactory factory) {
if (null == name || null == factory) throw new NullPointerException();
nameAssociations.put(name, factory);
}
/**
* Registers a {@link GremlinScriptEngineFactory} to handle a mime type. Overrides any such association found using
* the discovery mechanism.
*
* @param type The mime type to be associated with the {@link GremlinScriptEngineFactory}.
* @param factory The class to associate with the given mime type.
* @throws NullPointerException if any of the parameters is null.
*/
@Override
public void registerEngineMimeType(final String type, final GremlinScriptEngineFactory factory) {
if (null == type || null == factory) throw new NullPointerException();
mimeTypeAssociations.put(type, factory);
}
/**
* Registers a {@link GremlinScriptEngineFactory} to handle an extension. Overrides any such association found
* using the discovery mechanism.
*
* @param extension The extension type to be associated with the {@link GremlinScriptEngineFactory}
* @param factory The class to associate with the given extension.
* @throws NullPointerException if any of the parameters is null.
*/
@Override
public void registerEngineExtension(final String extension, final GremlinScriptEngineFactory factory) {
if (null == extension || null == factory) throw new NullPointerException();
extensionAssociations.put(extension, factory);
}
private ServiceLoader getServiceLoader(final ClassLoader loader) {
if (loader != null) {
return ServiceLoader.load(GremlinScriptEngineFactory.class, loader);
} else {
return ServiceLoader.loadInstalled(GremlinScriptEngineFactory.class);
}
}
private void initEngines(final ClassLoader loader) {
Iterator itty;
try {
final ServiceLoader sl = AccessController.doPrivileged(
(PrivilegedAction>) () -> getServiceLoader(loader));
itty = sl.iterator();
} catch (ServiceConfigurationError err) {
logger.error("Can't find GremlinScriptEngineFactory providers: " + err.getMessage(), err);
// do not throw any exception here. user may want to manager their own factories using this manager
// by explicit registration (by registerXXX) methods.
return;
}
try {
while (itty.hasNext()) {
try {
final GremlinScriptEngineFactory factory = itty.next();
factory.setCustomizerManager(this);
engineSpis.add(factory);
} catch (ServiceConfigurationError err) {
logger.error("GremlinScriptEngineManager providers.next(): " + err.getMessage(), err);
}
}
} catch (ServiceConfigurationError err) {
logger.error("GremlinScriptEngineManager providers.hasNext(): " + err.getMessage(), err);
// do not throw any exception here. user may want to manage their own factories using this manager
// by explicit registration (by registerXXX) methods.
}
}
private GremlinScriptEngine createGremlinScriptEngine(final GremlinScriptEngineFactory spi) {
final GremlinScriptEngine engine = spi.getScriptEngine();
// merge in bindings that are marked with global scope. these get applied to all GremlinScriptEngine instances
getCustomizers(spi.getEngineName()).stream()
.filter(p -> p instanceof BindingsCustomizer)
.map(p -> ((BindingsCustomizer) p))
.filter(bc -> bc.getScope() == ScriptContext.GLOBAL_SCOPE)
.flatMap(bc -> bc.getBindings().entrySet().stream())
.forEach(kv -> {
if (globalScope.containsKey(kv.getKey())) {
logger.warn("Overriding the global binding [{}] - was [{}] and is now [{}]",
kv.getKey(), globalScope.get(kv.getKey()), kv.getValue());
}
globalScope.put(kv.getKey(), kv.getValue());
});
engine.setBindings(getBindings(), ScriptContext.GLOBAL_SCOPE);
// merge in bindings that are marked with engine scope. there typically won't be any of these but it's just
// here for completeness. bindings will typically apply with global scope only as engine scope will generally
// be overridden at the time of eval() with the bindings that are supplied to it
getCustomizers(spi.getEngineName()).stream()
.filter(p -> p instanceof BindingsCustomizer)
.map(p -> ((BindingsCustomizer) p))
.filter(bc -> bc.getScope() == ScriptContext.ENGINE_SCOPE)
.forEach(bc -> engine.getBindings(ScriptContext.ENGINE_SCOPE).putAll(bc.getBindings()));
final List scriptCustomizers = getCustomizers(spi.getEngineName()).stream()
.filter(p -> p instanceof ScriptCustomizer)
.map(p -> ((ScriptCustomizer) p))
.collect(Collectors.toList());
// since the bindings aren't added until after the ScriptEngine is constructed, running init scripts that
// require bindings creates a problem. as a result, init scripts are applied here
scriptCustomizers.stream().flatMap(sc -> sc.getScripts().stream()).
map(l -> String.join(System.lineSeparator(), l)).forEach(initScript -> {
try {
// need to apply global bindings here as part of the engine or else they don't get their binding types
// registered by certain GremlinScriptEngine instances (pretty much talking about gremlin-groovy here)
// where type checking is made important. this may not be a good generic way to handled this in the
// long run, but for now we only have two GremlinScriptEngines to be concerned about so thus far it
// presents no real pains. global bindings are applied automatically to the context via
// AbstractScriptEngine.getScriptContext() - passing them again here to eval() will just make the
// global bindings behave as engine bindings and then you get weird things happening (like local vars
// becoming global).
final Object initializedBindings = engine.eval(initScript);
if (initializedBindings != null && initializedBindings instanceof Map)
((Map) initializedBindings).forEach((k,v) -> put(k,v));
} catch (Exception ex) {
throw new IllegalStateException(ex);
}
});
return engine;
}
}
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