WW-3691 Converts BackgroundProcess into interface and uses Executor to execute BackgroundProcess

Author: lukaszlenart

apps/showcase/src/main/java/org/apache/struts2/showcase/wait/ThreadPoolExecutorProvider.java

@@ -0,0 +1,56 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.apache.struts2.showcase.wait;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.apache.struts2.interceptor.exec.ExecutorProvider;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.LinkedBlockingDeque;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+
+public class ThreadPoolExecutorProvider implements ExecutorProvider {
+
+    private static final Logger LOG = LogManager.getLogger(ThreadPoolExecutorProvider.class);
+
+    private final ExecutorService executor;
+
+    public ThreadPoolExecutorProvider() {
+        this.executor = new ThreadPoolExecutor(1, 2, 0L, TimeUnit.MILLISECONDS, new LinkedBlockingDeque<>());
+    }
+
+    @Override
+    public void execute(Runnable task) {
+        LOG.info("Executing task: {}", task);
+        executor.execute(task);
+    }
+
+    @Override
+    public boolean isShutdown() {
+        return executor.isShutdown();
+    }
+
+    @Override
+    public void shutdown() {
+        LOG.info("Shutting down executor");
+        executor.shutdown();
+    }
+}

apps/showcase/src/main/resources/struts-wait.xml

@@ -24,6 +24,9 @@
 	"https://struts.apache.org/dtds/struts-2.5.dtd">
 
 <struts>
+
+    <bean type="org.apache.struts2.interceptor.exec.ExecutorProvider" class="org.apache.struts2.showcase.wait.ThreadPoolExecutorProvider"/>
+
     <package name="wait" extends="struts-default" namespace="/wait">
 
         <action name="example1">

core/src/main/java/org/apache/struts2/interceptor/ExecuteAndWaitInterceptor.java

@@ -22,12 +22,17 @@
 import com.opensymphony.xwork2.ActionContext;
 import com.opensymphony.xwork2.ActionInvocation;
 import com.opensymphony.xwork2.ActionProxy;
+import com.opensymphony.xwork2.config.entities.ResultConfig;
 import com.opensymphony.xwork2.inject.Container;
 import com.opensymphony.xwork2.inject.Inject;
 import com.opensymphony.xwork2.interceptor.MethodFilterInterceptor;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.apache.struts2.ServletActionContext;
+import org.apache.struts2.interceptor.exec.BackgroundProcess;
+import org.apache.struts2.interceptor.exec.ExecutorProvider;
+import org.apache.struts2.interceptor.exec.StrutsBackgroundProcess;
+import org.apache.struts2.interceptor.exec.StrutsExecutorProvider;
 import org.apache.struts2.util.TokenHelper;
 import org.apache.struts2.views.freemarker.FreemarkerResult;
 
@@ -84,7 +89,7 @@
  * <!-- END SNIPPET: description -->
  *
  * <p><u>Interceptor parameters:</u></p>
- *
+ * <p>
  * <!-- START SNIPPET: parameters -->
  *
  * <ul>
@@ -94,11 +99,11 @@
  * <li>delaySleepInterval (optional) - only used with delay. Used for waking up at certain intervals to check if the background process is already done. Default is 100 millis.</li>
  *
  * </ul>
- *
+ * <p>
  * <!-- END SNIPPET: parameters -->
  *
  * <p><u>Extending the interceptor:</u></p>
- *
+ * <p>
  * <!-- START SNIPPET: extending -->
  * <p>
  * If you wish to make special preparations before and/or after the invocation of the background thread, you can extend
@@ -167,9 +172,8 @@
  *     &lt;result name="success"&gt;longRunningAction-success.jsp&lt;/result&gt;
  * &lt;/action&gt;
  * </pre>
- *
+ * <p>
  * <!-- END SNIPPET: example -->
- *
  */
 public class ExecuteAndWaitInterceptor extends MethodFilterInterceptor {
 
@@ -186,30 +190,35 @@ public class ExecuteAndWaitInterceptor extends MethodFilterInterceptor {
     private int threadPriority = Thread.NORM_PRIORITY;
 
     private Container container;
+    private ExecutorProvider executor;
 
     @Inject
     public void setContainer(Container container) {
         this.container = container;
     }
 
+    @Inject(required = false)
+    public void setExecutorProvider(ExecutorProvider executorProvider) {
+        this.executor = executorProvider;
+    }
+
     /**
      * Creates a new background process
      *
-     * @param name The process name
+     * @param name             The process name
      * @param actionInvocation The action invocation
-     * @param threadPriority The thread priority
+     * @param threadPriority   The thread priority
      * @return The new process
      */
     protected BackgroundProcess getNewBackgroundProcess(String name, ActionInvocation actionInvocation, int threadPriority) {
-        return new BackgroundProcess(name + "BackgroundThread", actionInvocation, threadPriority);
+        return new StrutsBackgroundProcess(actionInvocation, name + "_background-process", threadPriority);
     }
 
     /**
      * Returns the name to associate the background process.  Override to change the way background processes
      * are mapped to requests.
      *
      * @param proxy action proxy
-     *
      * @return the name of the background thread
      */
     protected String getBackgroundProcessName(ActionProxy proxy) {
@@ -223,10 +232,10 @@ protected String doIntercept(ActionInvocation actionInvocation) throws Exception
         ActionProxy proxy = actionInvocation.getProxy();
         String name = getBackgroundProcessName(proxy);
         ActionContext context = actionInvocation.getInvocationContext();
-        Map session = context.getSession();
+        Map<String, Object> session = context.getSession();
         HttpSession httpSession = ServletActionContext.getRequest().getSession(true);
 
-        Boolean secondTime  = true;
+        Boolean secondTime = true;
         if (executeAfterValidationPass) {
             secondTime = (Boolean) context.get(KEY);
             if (secondTime == null) {
@@ -250,25 +259,30 @@ protected String doIntercept(ActionInvocation actionInvocation) throws Exception
             }
 
             if ((!executeAfterValidationPass || secondTime) && bp == null) {
-                bp = getNewBackgroundProcess(name, actionInvocation, threadPriority);
+                bp = getNewBackgroundProcess(name, actionInvocation, threadPriority).prepare();
                 session.put(KEY + name, bp);
+                if (executor.isShutdown()) {
+                    LOG.warn("Executor is shutting down, cannot execute a new process");
+                    return actionInvocation.invoke();
+                }
+                executor.execute(bp);
                 performInitialDelay(bp); // first time let some time pass before showing wait page
                 secondTime = false;
             }
 
             if ((!executeAfterValidationPass || !secondTime) && bp != null && !bp.isDone()) {
                 actionInvocation.getStack().push(bp.getAction());
 
-				final String token = TokenHelper.getToken();
-				if (token != null) {
-					TokenHelper.setSessionToken(TokenHelper.getTokenName(), token);
+                final String token = TokenHelper.getToken();
+                if (token != null) {
+                    TokenHelper.setSessionToken(TokenHelper.getTokenName(), token);
                 }
 
-                Map results = proxy.getConfig().getResults();
+                Map<String, ResultConfig> results = proxy.getConfig().getResults();
                 if (!results.containsKey(WAIT)) {
-                	LOG.warn("ExecuteAndWait interceptor has detected that no result named 'wait' is available. " +
-                            "Defaulting to a plain built-in wait page. It is highly recommend you " +
-                            "provide an action-specific or global result named '{}'.", WAIT);
+                    LOG.warn("ExecuteAndWait interceptor has detected that no result named 'wait' is available. " +
+                        "Defaulting to a plain built-in wait page. It is highly recommend you " +
+                        "provide an action-specific or global result named '{}'.", WAIT);
                     // no wait result? hmm -- let's try to do dynamically put it in for you!
 
                     //we used to add a fake "wait" result here, since the configuration is unmodifiable, that is no longer
@@ -286,7 +300,7 @@ protected String doIntercept(ActionInvocation actionInvocation) throws Exception
                 session.remove(KEY + name);
                 actionInvocation.getStack().push(bp.getAction());
 
-                // if an exception occured during action execution, throw it here
+                // if an exception occurred during action execution, throw it here
                 if (bp.getException() != null) {
                     throw bp.getException();
                 }
@@ -369,5 +383,17 @@ public void setExecuteAfterValidationPass(boolean executeAfterValidationPass) {
         this.executeAfterValidationPass = executeAfterValidationPass;
     }
 
+    @Override
+    public void init() {
+        super.init();
+        if (executor == null) {
+            executor = new StrutsExecutorProvider();
+        }
+    }
 
+    @Override
+    public void destroy() {
+        super.destroy();
+        executor.shutdown();
+    }
 }

core/src/main/java/org/apache/struts2/interceptor/exec/BackgroundProcess.java

@@ -0,0 +1,41 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.apache.struts2.interceptor.exec;
+
+import com.opensymphony.xwork2.ActionInvocation;
+import org.apache.struts2.interceptor.ExecuteAndWaitInterceptor;
+
+/**
+ * Interface used to create a background process which will be executed by
+ * {@link ExecuteAndWaitInterceptor}
+ */
+public interface BackgroundProcess extends Runnable {
+
+    BackgroundProcess prepare();
+
+    Object getAction();
+
+    ActionInvocation getInvocation();
+
+    String getResult();
+
+    Exception getException();
+
+    boolean isDone();
+}

core/src/main/java/org/apache/struts2/interceptor/exec/ExecutorProvider.java

@@ -0,0 +1,38 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.apache.struts2.interceptor.exec;
+
+import java.util.concurrent.ExecutorService;
+
+/**
+ * Interface mimics {@link ExecutorService} to be used with
+ * {@link org.apache.struts2.interceptor.ExecuteAndWaitInterceptor}
+ * to execute {@link BackgroundProcess}
+ *
+ * @since 6.1.0
+ */
+public interface ExecutorProvider {
+
+    void execute(Runnable task);
+
+    boolean isShutdown();
+
+    void shutdown();
+
+}