#1 replace creation of ScriptEngines bound to each thread with Thread…

…Local with a pool of Nashorn ScriptEngines (w/ use of commons-pool)

build.gradle

@@ -27,6 +27,7 @@ dependencies {
     compile 'org.glassfish.jersey.media:jersey-media-json-jackson:2.22.2'
     compile 'javax.enterprise:cdi-api:2.0-EDR1'
     compile 'org.jboss.weld.servlet:weld-servlet-core:3.0.0.Alpha12'
+    compile 'org.apache.commons:commons-pool2:2.4.2'
     // some needed webjars (frontend-stuff)
     compile 'org.webjars:jquery:2.2.3'
     compile 'org.webjars:materializecss:0.97.5'

pom.xml

@@ -64,6 +64,11 @@
             <artifactId>weld-servlet-core</artifactId>
             <version>3.0.0.Alpha12</version>
         </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-pool2</artifactId>
+            <version>2.4.2</version>
+        </dependency>
         <dependency>
             <groupId>org.webjars</groupId>
             <artifactId>jquery</artifactId>

src/main/java/dasniko/ozark/react/NashornPool.java

@@ -0,0 +1,34 @@
+package dasniko.ozark.react;
+
+import org.apache.commons.pool2.ObjectPool;
+import org.apache.commons.pool2.impl.GenericObjectPool;
+import org.apache.commons.pool2.impl.GenericObjectPoolConfig;
+
+import javax.enterprise.context.ApplicationScoped;
+import javax.enterprise.context.Initialized;
+import javax.enterprise.event.Observes;
+import javax.enterprise.inject.Produces;
+import javax.script.ScriptEngine;
+
+/**
+ * @author Niko Köbler, http://www.n-k.de, @dasniko
+ */
+@ApplicationScoped
+public class NashornPool {
+
+    private GenericObjectPool<ScriptEngine> pool;
+
+    public void init(@Observes @Initialized(ApplicationScoped.class) Object init) {
+        GenericObjectPoolConfig config = new GenericObjectPoolConfig();
+        config.setMinIdle(1);
+
+        pool = new GenericObjectPool<>(new NashornPoolFactory(), config);
+    }
+
+    @Produces
+    public ObjectPool<ScriptEngine> getObjectPool() {
+        return this.pool;
+    }
+
+
+}

src/main/java/dasniko/ozark/react/NashornPoolFactory.java

@@ -0,0 +1,74 @@
+package dasniko.ozark.react;
+
+import org.apache.commons.pool2.BasePooledObjectFactory;
+import org.apache.commons.pool2.PooledObject;
+import org.apache.commons.pool2.impl.DefaultPooledObject;
+
+import javax.script.ScriptEngine;
+import javax.script.ScriptEngineManager;
+import javax.script.ScriptException;
+import java.io.File;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.net.URISyntaxException;
+import java.net.URL;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * @author Niko Köbler, http://www.n-k.de, @dasniko
+ */
+public class NashornPoolFactory extends BasePooledObjectFactory<ScriptEngine> {
+
+    private static final String DEFAULT_JS_RESOURCE_PATH = "/js";
+    private static final String RESOURCE_PATH = System.getProperty("mvc.reactjs.resourcePath", DEFAULT_JS_RESOURCE_PATH);
+
+    @Override
+    public ScriptEngine create() throws Exception {
+        ScriptEngine nashorn = new ScriptEngineManager().getEngineByName("nashorn");
+
+        // initial basically needed files for dealing with react
+        List<String> jsResources = new ArrayList<>();
+        jsResources.add("nashorn-polyfill.js");
+
+        // add all resources from custom application
+        jsResources.addAll(getAllFilesFromResourcePath());
+        // and load/evaluate them within nashorn
+        jsResources.forEach(p -> {
+            try {
+                nashorn.eval(read(p));
+            } catch (ScriptException e) {
+                throw new RuntimeException(e);
+            }
+        });
+
+        return nashorn;
+    }
+
+    @Override
+    public PooledObject<ScriptEngine> wrap(ScriptEngine scriptEngine) {
+        return new DefaultPooledObject<>(scriptEngine);
+    }
+
+    private List<String> getAllFilesFromResourcePath() {
+        URL url = this.getClass().getClassLoader().getResource(RESOURCE_PATH);
+        if (url != null && url.getProtocol().equals("file")) {
+            try {
+                return Arrays.stream(new File(url.toURI()).list()).map(p -> RESOURCE_PATH + "/" + p).collect(Collectors.toList());
+            } catch (URISyntaxException e) {
+                throw new RuntimeException(e);
+            }
+        } else {
+            // TODO do something
+            return new ArrayList<>();
+        }
+    }
+
+    private Reader read(String path) {
+        InputStream in = getClass().getClassLoader().getResourceAsStream(path);
+        return new InputStreamReader(in);
+    }
+}

src/main/java/dasniko/ozark/react/React.java

@@ -1,82 +1,34 @@
 package dasniko.ozark.react;
 
 import jdk.nashorn.api.scripting.ScriptObjectMirror;
+import org.apache.commons.pool2.ObjectPool;
 
+import javax.inject.Inject;
 import javax.script.Invocable;
 import javax.script.ScriptEngine;
-import javax.script.ScriptEngineManager;
-import javax.script.ScriptException;
-import java.io.File;
-import java.io.InputStream;
-import java.io.InputStreamReader;
-import java.io.Reader;
-import java.net.URISyntaxException;
-import java.net.URL;
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.List;
-import java.util.stream.Collectors;
 
 /**
  * @author Niko Köbler, http://www.n-k.de, @dasniko
  */
 public class React {
 
-    private static final String DEFAULT_JS_RESOURCE_PATH = "/js";
-    private static final String RESOURCE_PATH = System.getProperty("mvc.reactjs.resourcePath", DEFAULT_JS_RESOURCE_PATH);
-
-    private ThreadLocal<ScriptEngine> engineHolder = ThreadLocal.withInitial(() -> {
-        ScriptEngine nashorn = new ScriptEngineManager().getEngineByName("nashorn");
-
-        // initial basically needed files for dealing with react
-        List<String> jsResources = new ArrayList<>();
-        jsResources.add("nashorn-polyfill.js");
-
-        // add all resources from custom application
-        jsResources.addAll(getAllFilesFromResourcePath());
-        // and load/evaluate them within nashorn
-        jsResources.forEach(p -> {
-            try {
-                nashorn.eval(read(p));
-            } catch (ScriptException e) {
-                throw new RuntimeException(e);
-            }
-        });
-
-        return nashorn;
-    });
-
-    private List<String> getAllFilesFromResourcePath() {
-        URL url = this.getClass().getClassLoader().getResource(RESOURCE_PATH);
-        if (url != null && url.getProtocol().equals("file")) {
-            try {
-                return Arrays.asList(new File(url.toURI()).list()).stream().map(p -> RESOURCE_PATH + "/" + p).collect(Collectors.toList());
-            } catch (URISyntaxException e) {
-                throw new RuntimeException(e);
-            }
-        } else {
-            // TODO do something
-            return new ArrayList<>();
-        }
-    }
+    @Inject
+    private ObjectPool<ScriptEngine> scriptEnginePool;
 
     String render(String function, Object object) {
         try {
             Object html;
+            ScriptEngine scriptEngine = scriptEnginePool.borrowObject();
             if (function.contains(".")) {
                 String[] parts = function.split("\\.");
-                html = ((ScriptObjectMirror) engineHolder.get().get(parts[0])).callMember(parts[1], object);
+                html = ((ScriptObjectMirror) scriptEngine.get(parts[0])).callMember(parts[1], object);
             } else {
-                html = ((Invocable) engineHolder.get()).invokeFunction(function, object);
+                html = ((Invocable) scriptEngine).invokeFunction(function, object);
             }
+            scriptEnginePool.returnObject(scriptEngine);
             return String.valueOf(html);
         } catch (Exception e) {
             throw new IllegalStateException("failed to render react component", e);
         }
     }
-
-    private Reader read(String path) {
-        InputStream in = getClass().getClassLoader().getResourceAsStream(path);
-        return new InputStreamReader(in);
-    }
-}
+}