StandardScriptUtils.retrieveEngineByName for lookup with descriptive exception message

Also revised StandardScriptFactory for finer-grained template methods, added further configuration variants to StandardScriptEvaluator, and identified thread-local ScriptEngine instances in ScriptTemplateView by appropriate key.

Issue: SPR-13491
Issue: SPR-13487

spring-context/src/main/java/org/springframework/scripting/support/StandardScriptEvaluator.java

 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2015 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,7 +22,6 @@ import javax.script.Bindings;
 import javax.script.ScriptEngine;
 import javax.script.ScriptEngineManager;
 import javax.script.ScriptException;
-import javax.script.SimpleBindings;
 
 import org.springframework.beans.factory.BeanClassLoaderAware;
 import org.springframework.core.io.Resource;
@@ -45,34 +44,74 @@ public class StandardScriptEvaluator implements ScriptEvaluator, BeanClassLoader
 
 	private volatile ScriptEngineManager scriptEngineManager;
 
-	private String language;
+	private String engineName;
 
 
 	/**
-	 * Construct a new StandardScriptEvaluator.
+	 * Construct a new {@code StandardScriptEvaluator}.
 	 */
 	public StandardScriptEvaluator() {
 	}
 
 	/**
-	 * Construct a new StandardScriptEvaluator.
+	 * Construct a new {@code StandardScriptEvaluator} for the given class loader.
 	 * @param classLoader the class loader to use for script engine detection
 	 */
 	public StandardScriptEvaluator(ClassLoader classLoader) {
 		this.scriptEngineManager = new ScriptEngineManager(classLoader);
 	}
 
-
-	@Override
-	public void setBeanClassLoader(ClassLoader classLoader) {
-		this.scriptEngineManager = new ScriptEngineManager(classLoader);
+	/**
+	 * Construct a new {@code StandardScriptEvaluator} for the given JSR-223
+	 * {@link ScriptEngineManager} to obtain script engines from.
+	 * @param scriptEngineManager the ScriptEngineManager (or subclass thereof) to use
+	 * @since 4.2.2
+	 */
+	public StandardScriptEvaluator(ScriptEngineManager scriptEngineManager) {
+		this.scriptEngineManager = scriptEngineManager;
 	}
 
+
 	/**
-	 * Set the name of language meant for evaluation the scripts (e.g. "Groovy").
+	 * Set the name of the language meant for evaluating the scripts (e.g. "Groovy").
+	 * <p>This is effectively an alias for {@link #setEngineName "engineName"},
+	 * potentially (but not yet) providing common abbreviations for certain languages
+	 * beyond what the JSR-223 script engine factory exposes.
+	 * @see #setEngineName
 	 */
 	public void setLanguage(String language) {
-		this.language = language;
+		this.engineName = language;
+	}
+
+	/**
+	 * Set the name of the script engine for evaluating the scripts (e.g. "Groovy"),
+	 * as exposed by the JSR-223 script engine factory.
+	 * @since 4.2.2
+	 * @see #setLanguage
+	 */
+	public void setEngineName(String engineName) {
+		this.engineName = engineName;
+	}
+
+	/**
+	 * Set the globally scoped bindings on the underlying script engine manager,
+	 * shared by all scripts, as an alternative to script argument bindings.
+	 * @since 4.2.2
+	 * @see #evaluate(ScriptSource, Map)
+	 * @see javax.script.ScriptEngineManager#setBindings(Bindings)
+	 * @see javax.script.SimpleBindings
+	 */
+	public void setGlobalBindings(Map<String, Object> globalBindings) {
+		if (globalBindings != null) {
+			this.scriptEngineManager.setBindings(StandardScriptUtils.getBindings(globalBindings));
+		}
+	}
+
+	@Override
+	public void setBeanClassLoader(ClassLoader classLoader) {
+		if (this.scriptEngineManager == null) {
+			this.scriptEngineManager = new ScriptEngineManager(classLoader);
+		}
 	}
 
 
@@ -82,12 +121,16 @@ public class StandardScriptEvaluator implements ScriptEvaluator, BeanClassLoader
 	}
 
 	@Override
-	public Object evaluate(ScriptSource script, Map<String, Object> arguments) {
+	public Object evaluate(ScriptSource script, Map<String, Object> argumentBindings) {
 		ScriptEngine engine = getScriptEngine(script);
-		Bindings bindings = (!CollectionUtils.isEmpty(arguments) ? new SimpleBindings(arguments) : null);
 		try {
-			return (bindings != null ? engine.eval(script.getScriptAsString(), bindings) :
-					engine.eval(script.getScriptAsString()));
+			if (CollectionUtils.isEmpty(argumentBindings)) {
+				return engine.eval(script.getScriptAsString());
+			}
+			else {
+				Bindings bindings = StandardScriptUtils.getBindings(argumentBindings);
+				return engine.eval(script.getScriptAsString(), bindings);
+			}
 		}
 		catch (IOException ex) {
 			throw new ScriptCompilationException(script, "Cannot access script", ex);
@@ -106,12 +149,9 @@ public class StandardScriptEvaluator implements ScriptEvaluator, BeanClassLoader
 		if (this.scriptEngineManager == null) {
 			this.scriptEngineManager = new ScriptEngineManager();
 		}
-		if (StringUtils.hasText(this.language)) {
-			ScriptEngine engine = this.scriptEngineManager.getEngineByName(this.language);
-			if (engine == null) {
-				throw new IllegalStateException("No matching engine found for language '" + this.language + "'");
-			}
-			return engine;
+
+		if (StringUtils.hasText(this.engineName)) {
+			return StandardScriptUtils.retrieveEngineByName(this.scriptEngineManager, this.engineName);
 		}
 		else if (script instanceof ResourceScriptSource) {
 			Resource resource = ((ResourceScriptSource) script).getResource();

spring-context/src/main/java/org/springframework/scripting/support/StandardScriptFactory.java

@@ -109,31 +109,6 @@ public class StandardScriptFactory implements ScriptFactory, BeanClassLoaderAwar
 		this.beanClassLoader = classLoader;
 	}
 
-	protected ScriptEngine retrieveScriptEngine(ScriptSource scriptSource) {
-		ScriptEngineManager scriptEngineManager = new ScriptEngineManager(this.beanClassLoader);
-		if (this.scriptEngineName != null) {
-			ScriptEngine engine = scriptEngineManager.getEngineByName(this.scriptEngineName);
-			if (engine == null) {
-				throw new IllegalStateException("Script engine named '" + this.scriptEngineName + "' not found");
-			}
-			return engine;
-		}
-		if (scriptSource instanceof ResourceScriptSource) {
-			String filename = ((ResourceScriptSource) scriptSource).getResource().getFilename();
-			if (filename != null) {
-				String extension = StringUtils.getFilenameExtension(filename);
-				if (extension != null) {
-					ScriptEngine engine = scriptEngineManager.getEngineByExtension(extension);
-					if (engine != null) {
-						return engine;
-					}
-				}
-			}
-		}
-		return null;
-	}
-
-
 	@Override
 	public String getScriptSourceLocator() {
 		return this.scriptSourceLocator;
@@ -157,54 +132,18 @@ public class StandardScriptFactory implements ScriptFactory, BeanClassLoaderAwar
 	public Object getScriptedObject(ScriptSource scriptSource, Class<?>... actualInterfaces)
 			throws IOException, ScriptCompilationException {
 
-		Object script;
-
-		try {
-			if (this.scriptEngine == null) {
-				this.scriptEngine = retrieveScriptEngine(scriptSource);
-				if (this.scriptEngine == null) {
-					throw new IllegalStateException("Could not determine script engine for " + scriptSource);
-				}
-			}
-			script = this.scriptEngine.eval(scriptSource.getScriptAsString());
-		}
-		catch (Exception ex) {
-			throw new ScriptCompilationException(scriptSource, ex);
-		}
+		Object script = evaluateScript(scriptSource);
 
 		if (!ObjectUtils.isEmpty(actualInterfaces)) {
 			boolean adaptationRequired = false;
 			for (Class<?> requestedIfc : actualInterfaces) {
-				if (!requestedIfc.isInstance(script)) {
+				if (script instanceof Class ? !requestedIfc.isAssignableFrom((Class<?>) script) :
+						!requestedIfc.isInstance(script)) {
 					adaptationRequired = true;
 				}
 			}
 			if (adaptationRequired) {
-				Class<?> adaptedIfc;
-				if (actualInterfaces.length == 1) {
-					adaptedIfc = actualInterfaces[0];
-				}
-				else {
-					adaptedIfc = ClassUtils.createCompositeInterface(actualInterfaces, this.beanClassLoader);
-				}
-				if (adaptedIfc != null) {
-					if (!(this.scriptEngine instanceof Invocable)) {
-						throw new ScriptCompilationException(scriptSource,
-								"ScriptEngine must implement Invocable in order to adapt it to an interface: " +
-										this.scriptEngine);
-					}
-					Invocable invocable = (Invocable) this.scriptEngine;
-					if (script != null) {
-						script = invocable.getInterface(script, adaptedIfc);
-					}
-					if (script == null) {
-						script = invocable.getInterface(adaptedIfc);
-						if (script == null) {
-							throw new ScriptCompilationException(scriptSource,
-									"Could not adapt script to interface [" + adaptedIfc.getName() + "]");
-						}
-					}
-				}
+				script = adaptToInterfaces(script, scriptSource, actualInterfaces);
 			}
 		}
 
@@ -226,6 +165,75 @@ public class StandardScriptFactory implements ScriptFactory, BeanClassLoaderAwar
 		return script;
 	}
 
+	protected Object evaluateScript(ScriptSource scriptSource) {
+		try {
+			if (this.scriptEngine == null) {
+				this.scriptEngine = retrieveScriptEngine(scriptSource);
+				if (this.scriptEngine == null) {
+					throw new IllegalStateException("Could not determine script engine for " + scriptSource);
+				}
+			}
+			return this.scriptEngine.eval(scriptSource.getScriptAsString());
+		}
+		catch (Exception ex) {
+			throw new ScriptCompilationException(scriptSource, ex);
+		}
+	}
+
+	protected ScriptEngine retrieveScriptEngine(ScriptSource scriptSource) {
+		ScriptEngineManager scriptEngineManager = new ScriptEngineManager(this.beanClassLoader);
+
+		if (this.scriptEngineName != null) {
+			return StandardScriptUtils.retrieveEngineByName(scriptEngineManager, this.scriptEngineName);
+		}
+
+		if (scriptSource instanceof ResourceScriptSource) {
+			String filename = ((ResourceScriptSource) scriptSource).getResource().getFilename();
+			if (filename != null) {
+				String extension = StringUtils.getFilenameExtension(filename);
+				if (extension != null) {
+					ScriptEngine engine = scriptEngineManager.getEngineByExtension(extension);
+					if (engine != null) {
+						return engine;
+					}
+				}
+			}
+		}
+
+		return null;
+	}
+
+	protected Object adaptToInterfaces(Object script, ScriptSource scriptSource, Class<?>... actualInterfaces) {
+		Class<?> adaptedIfc;
+		if (actualInterfaces.length == 1) {
+			adaptedIfc = actualInterfaces[0];
+		}
+		else {
+			adaptedIfc = ClassUtils.createCompositeInterface(actualInterfaces, this.beanClassLoader);
+		}
+
+		if (adaptedIfc != null) {
+			if (!(this.scriptEngine instanceof Invocable)) {
+				throw new ScriptCompilationException(scriptSource,
+						"ScriptEngine must implement Invocable in order to adapt it to an interface: " +
+								this.scriptEngine);
+			}
+			Invocable invocable = (Invocable) this.scriptEngine;
+			if (script != null) {
+				script = invocable.getInterface(script, adaptedIfc);
+			}
+			if (script == null) {
+				script = invocable.getInterface(adaptedIfc);
+				if (script == null) {
+					throw new ScriptCompilationException(scriptSource,
+							"Could not adapt script to interface [" + adaptedIfc.getName() + "]");
+				}
+			}
+		}
+
+		return script;
+	}
+
 	@Override
 	public Class<?> getScriptedObjectType(ScriptSource scriptSource)
 			throws IOException, ScriptCompilationException {

spring-context/src/main/java/org/springframework/scripting/support/StandardScriptUtils.java

+/*
+ * Copyright 2002-2015 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.scripting.support;
+
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import javax.script.Bindings;
+import javax.script.ScriptContext;
+import javax.script.ScriptEngine;
+import javax.script.ScriptEngineFactory;
+import javax.script.ScriptEngineManager;
+import javax.script.SimpleBindings;
+
+/**
+ * Common operations for dealing with a JSR-223 {@link ScriptEngine}.
+ *
+ * @author Juergen Hoeller
+ * @since 4.2.2
+ */
+public abstract class StandardScriptUtils {
+
+	/**
+	 * Retrieve a {@link ScriptEngine} from the given {@link ScriptEngineManager}
+	 * by name, delegating to {@link ScriptEngineManager#getEngineByName} but
+	 * throwing a descriptive exception if not found or if initialization failed.
+	 * @param scriptEngineManager the ScriptEngineManager to use
+	 * @param engineName the name of the engine
+	 * @return a corresponding ScriptEngine (never {@code null})
+	 * @throws IllegalArgumentException if no matching engine has been found
+	 * @throws IllegalStateException if no matching engine has been found or if
+	 */
+	public static ScriptEngine retrieveEngineByName(ScriptEngineManager scriptEngineManager, String engineName) {
+		ScriptEngine engine = scriptEngineManager.getEngineByName(engineName);
+		if (engine == null) {
+			Set<String> engineNames = new LinkedHashSet<String>();
+			for (ScriptEngineFactory engineFactory : scriptEngineManager.getEngineFactories()) {
+				List<String> factoryNames = engineFactory.getNames();
+				if (factoryNames.contains(engineName)) {
+					// Special case: getEngineByName returned null but engine is present...
+					// Let's assume it failed to initialize (which ScriptEngineManager silently swallows).
+					// If it happens to initialize fine now, alright, but we really expect an exception.
+					try {
+						engine = engineFactory.getScriptEngine();
+						engine.setBindings(scriptEngineManager.getBindings(), ScriptContext.GLOBAL_SCOPE);
+					}
+					catch (Throwable ex) {
+						throw new IllegalStateException("Script engine with name '" + engineName +
+								"' failed to initialize", ex);
+					}
+				}
+				engineNames.addAll(factoryNames);
+			}
+			throw new IllegalArgumentException("Script engine with name '" + engineName +
+					"' not found; registered engine names: " + engineNames);
+		}
+		return engine;
+	}
+
+	static Bindings getBindings(Map<String, Object> bindings) {
+		return (bindings instanceof Bindings ? (Bindings) bindings : new SimpleBindings(bindings));
+	}
+
+}

spring-webmvc/src/main/java/org/springframework/web/servlet/view/script/ScriptTemplateView.java

@@ -22,6 +22,8 @@ import java.net.URL;
 import java.net.URLClassLoader;
 import java.nio.charset.Charset;
 import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import javax.script.Invocable;
@@ -39,8 +41,10 @@ import org.springframework.core.NamedThreadLocal;
 import org.springframework.core.io.DefaultResourceLoader;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.ResourceLoader;
+import org.springframework.scripting.support.StandardScriptUtils;
 import org.springframework.util.Assert;
 import org.springframework.util.FileCopyUtils;
+import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 import org.springframework.web.servlet.view.AbstractUrlBasedView;
 
@@ -57,6 +61,7 @@ import org.springframework.web.servlet.view.AbstractUrlBasedView;
  * {@link ScriptTemplateConfigurer#setSharedEngine(Boolean)} for more details.
  *
  * @author Sebastien Deleuze
+ * @author Juergen Hoeller
  * @since 4.2
  * @see ScriptTemplateConfigurer
  * @see ScriptTemplateViewResolver
@@ -69,8 +74,9 @@ public class ScriptTemplateView extends AbstractUrlBasedView {
 
 	private static final String DEFAULT_RESOURCE_LOADER_PATH = "classpath:";
 
-	private static final ThreadLocal<ScriptEngine> engineHolder =
-			new NamedThreadLocal<ScriptEngine>("ScriptTemplateView engine");
+
+	private static final ThreadLocal<Map<Object, ScriptEngine>> enginesHolder =
+			new NamedThreadLocal<Map<Object, ScriptEngine>>("ScriptTemplateView engines");
 
 
 	private ScriptEngine engine;
@@ -87,9 +93,11 @@ public class ScriptTemplateView extends AbstractUrlBasedView {
 
 	private Charset charset;
 
+	private String resourceLoaderPath;
+
 	private ResourceLoader resourceLoader;
 
-	private String resourceLoaderPath;
+	private volatile ScriptEngineManager scriptEngineManager;
 
 
 	/**
@@ -234,12 +242,20 @@ public class ScriptTemplateView extends AbstractUrlBasedView {
 		Assert.isTrue(this.renderFunction != null, "The 'renderFunction' property must be defined.");
 	}
 
+
 	protected ScriptEngine getEngine() {
 		if (Boolean.FALSE.equals(this.sharedEngine)) {
-			ScriptEngine engine = engineHolder.get();
+			Map<Object, ScriptEngine> engines = enginesHolder.get();
+			if (engines == null) {
+				engines = new HashMap<Object, ScriptEngine>(4);
+				enginesHolder.set(engines);
+			}
+			Object engineKey = (!ObjectUtils.isEmpty(this.scripts) ?
+					new EngineKey(this.engineName, this.scripts) : this.engineName);
+			ScriptEngine engine = engines.get(engineKey);
 			if (engine == null) {
 				engine = createEngineFromName();
-				engineHolder.set(engine);
+				engines.put(engineKey, engine);
 			}
 			return engine;
 		}
@@ -250,21 +266,22 @@ public class ScriptTemplateView extends AbstractUrlBasedView {
 	}
 
 	protected ScriptEngine createEngineFromName() {
-		ScriptEngine engine = new ScriptEngineManager().getEngineByName(this.engineName);
-		if (engine == null) {
-			throw new IllegalStateException("No engine with name '" + this.engineName + "' found");
+		if (this.scriptEngineManager == null) {
+			this.scriptEngineManager = new ScriptEngineManager(getApplicationContext().getClassLoader());
 		}
+
+		ScriptEngine engine = StandardScriptUtils.retrieveEngineByName(this.scriptEngineManager, this.engineName);
 		loadScripts(engine);
 		return engine;
 	}
 
 	protected void loadScripts(ScriptEngine engine) {
-		if (this.scripts != null) {
+		if (!ObjectUtils.isEmpty(this.scripts)) {
 			try {
 				for (String script : this.scripts) {
 					Resource resource = this.resourceLoader.getResource(script);
 					if (!resource.exists()) {
-						throw new IllegalStateException("Resource " + script + " not found");
+						throw new IllegalStateException("Script resource [" + script + "] not found");
 					}
 					engine.eval(new InputStreamReader(resource.getInputStream()));
 				}
@@ -309,6 +326,7 @@ public class ScriptTemplateView extends AbstractUrlBasedView {
 		}
 	}
 
+
 	@Override
 	protected void prepareResponse(HttpServletRequest request, HttpServletResponse response) {
 		super.prepareResponse(request, response);
@@ -326,6 +344,7 @@ public class ScriptTemplateView extends AbstractUrlBasedView {
 			Invocable invocable = (Invocable) engine;
 			String url = getUrl();
 			String template = getTemplate(url);
+
 			Object html;
 			if (this.renderObject != null) {
 				Object thiz = engine.eval(this.renderObject);
@@ -334,6 +353,7 @@ public class ScriptTemplateView extends AbstractUrlBasedView {
 			else {
 				html = invocable.invokeFunction(this.renderFunction, template, model, url);
 			}
+
 			response.getWriter().write(String.valueOf(html));
 		}
 		catch (Exception ex) {
@@ -347,4 +367,39 @@ public class ScriptTemplateView extends AbstractUrlBasedView {
 		return FileCopyUtils.copyToString(reader);
 	}
 
+
+	/**
+	 * Key class for the {@code enginesHolder ThreadLocal}.
+	 * Only used if scripts have been specified; otherwise, the
+	 * {@code engineName String} will be used as cache key directly.
+	 */
+	private static class EngineKey {
+
+		private final String engineName;
+
+		private final String[] scripts;
+
+		public EngineKey(String engineName, String[] scripts) {
+			this.engineName = engineName;
+			this.scripts = scripts;
+		}
+
+		@Override
+		public boolean equals(Object other) {
+			if (this == other) {
+				return true;
+			}
+			if (!(other instanceof EngineKey)) {
+				return false;
+			}
+			EngineKey otherKey = (EngineKey) other;
+			return (this.engineName.equals(otherKey.engineName) && Arrays.equals(this.scripts, otherKey.scripts));
+		}
+
+		@Override
+		public int hashCode() {
+			return (this.engineName.hashCode() * 29 + Arrays.hashCode(this.scripts));
+		}
+	}
+
 }