Adding examples-servlet module to apex-pdp

Adding examples-servlet module to demonstrate the capability that
apex-pdp can be simply started as a servlet deployed in any application
server.

Change-Id: I5c9e323f1468cc14c6277c0037029679d00cd751
Issue-ID: POLICY-861
Signed-off-by: ramverma <ram.krishna.verma@ericsson.com>

2 files changed, 131 insertions, 0 deletions

diff --git a/examples/examples-servlet/src/main/java/org/onap/policy/apex/examples/servlet/ApexServletListener.java b/examples/examples-servlet/src/main/java/org/onap/policy/apex/examples/servlet/ApexServletListener.java
new file mode 100644
index 000000000..f6de1285e
--- /dev/null
+++ b/examples/examples-servlet/src/main/java/org/onap/policy/apex/examples/servlet/ApexServletListener.java
@@ -0,0 +1,104 @@
+/*-
+ * ============LICENSE_START=======================================================
+ *  Copyright (C) 2018 Ericsson. All rights reserved.
+ * ================================================================================
+ * 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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.apex.examples.servlet;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import javax.servlet.ServletContextEvent;
+import javax.servlet.ServletContextListener;
+import javax.servlet.annotation.WebListener;
+
+import org.onap.policy.apex.model.basicmodel.concepts.ApexException;
+import org.onap.policy.apex.model.basicmodel.concepts.ApexRuntimeException;
+import org.onap.policy.apex.service.engine.main.ApexMain;
+import org.slf4j.ext.XLogger;
+import org.slf4j.ext.XLoggerFactory;
+
+/**
+ * This class is a listener that is called when the servlet is started and stopped. It brings up the Apex engine on
+ * servlet start and shuts it down on servlet stop.
+ *
+ * @author Liam Fallon (liam.fallon@ericsson.com)
+ */
+@WebListener
+public class ApexServletListener implements ServletContextListener {
+    private static final XLogger LOGGER = XLoggerFactory.getXLogger(ApexServletListener.class);
+
+    // The Apex engine reference
+    private ApexMain apexMain;
+
+    /*
+     * (non-Javadoc)
+     *
+     * @see javax.servlet.ServletContextListener#contextInitialized(javax.servlet.ServletContextEvent)
+     */
+    @Override
+    public void contextInitialized(final ServletContextEvent servletContextEvent) {
+        // The web.xml file contains the context parameters for the Apex engine
+        final String configFileName = servletContextEvent.getServletContext().getInitParameter("config-file");
+        final String modelFileName = servletContextEvent.getServletContext().getInitParameter("model-file");
+
+        LOGGER.info("Apex Servliet has been started, config-file= " + configFileName + ", model-file=" + modelFileName);
+
+        // Check that a configuration file have been specified
+        if (servletContextEvent.getServletContext().getInitParameter("config-file") == null) {
+            final String errorMessage =
+                    "Apex servlet start failed, servlet parameter \"config-file\" has not been specified";
+            LOGGER.error("Apex servlet start failed, servlet parameter \"config-file\" has not been specified");
+            throw new ApexRuntimeException(errorMessage);
+        }
+
+        // Construct the Apex command line arguments
+        final List<String> argsList = new ArrayList<String>();
+        argsList.add("-config-file");
+        argsList.add(configFileName);
+
+        // Model file name is an optional parameter
+        if (modelFileName != null) {
+            argsList.add("-model-file");
+            argsList.add(modelFileName);
+        }
+
+        // Initialize apex
+        apexMain = new ApexMain(argsList.toArray(new String[argsList.size()]));
+    }
+
+
+    /*
+     * (non-Javadoc)
+     *
+     * @see javax.servlet.ServletContextListener#contextDestroyed(javax.servlet.ServletContextEvent)
+     */
+    @Override
+    public void contextDestroyed(final ServletContextEvent servletContextEvent) {
+        // Shut Apex down
+        try {
+            apexMain.shutdown();
+            apexMain = null;
+        } catch (final ApexException e) {
+            final String errorMessage = "Apex servlet stop did not execute normally";
+            LOGGER.error(errorMessage, e);
+        }
+
+        LOGGER.info("Apex Servliet has been stopped");
+    }
+}
diff --git a/examples/examples-servlet/src/main/java/org/onap/policy/apex/examples/servlet/package-info.java b/examples/examples-servlet/src/main/java/org/onap/policy/apex/examples/servlet/package-info.java
new file mode 100644
index 000000000..baf427e6d
--- /dev/null
+++ b/examples/examples-servlet/src/main/java/org/onap/policy/apex/examples/servlet/package-info.java
@@ -0,0 +1,27 @@
+/*-
+ * ============LICENSE_START=======================================================
+ *  Copyright (C) 2018 Ericsson. All rights reserved.
+ * ================================================================================
+ * 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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+/**
+ * Allows the APEX engine to be run as a servlet under the control of a Servlet container such as Apache Tomcat.
+ *
+ * @author Liam Fallon (liam.fallon@ericsson.com)
+ */
+
+package org.onap.policy.apex.examples.servlet;