Introduced MBeanPlugins #177

agent/core/src/main/java/org/jolokia/backend/MBeanServerExecutorLocal.java

@@ -126,8 +126,8 @@ public <R extends JmxRequest> Object handleRequest(JsonRequestHandler<R> pReques
     /**
      * Lifecycle method called at the end of life for this object.
      */
-    public void destroy() {
-        super.destroy();
+    public void unregisterFromMBeanNotifications() {
+        super.unregisterFromMBeanNotifications();
         mbeanServers.destroy();
     }
 

agent/core/src/main/java/org/jolokia/backend/MBeanServerHandler.java

@@ -8,12 +8,14 @@
 
 import org.jolokia.backend.executor.MBeanServerExecutor;
 import org.jolokia.backend.executor.NotChangedException;
+import org.jolokia.backend.plugin.*;
 import org.jolokia.config.ConfigKey;
 import org.jolokia.config.Configuration;
 import org.jolokia.detector.*;
 import org.jolokia.handler.JsonRequestHandler;
 import org.jolokia.request.JmxRequest;
-import org.jolokia.util.*;
+import org.jolokia.util.LogHandler;
+import org.jolokia.util.ServiceObjectFactory;
 
 /*
  * Copyright 2009-2013 Roland Huss
@@ -69,8 +71,45 @@ public MBeanServerHandler(Configuration pConfig, LogHandler pLogHandler) {
         mBeanServerManager = new MBeanServerExecutorLocal(detectors);
         initServerHandle(pConfig, pLogHandler, detectors);
         initMBean();
+        initPlugins(pLogHandler);
     }
 
+    private void initPlugins(LogHandler pLogHandler) {
+        List<MBeanPlugin> plugins = ServiceObjectFactory.createServiceObjects("META-INF/mbean-plugins");
+        if (plugins.size() > 0) {
+            MBeanPluginContext ctx = createMBeanPluginContext();
+            for (MBeanPlugin plugin : plugins) {
+                plugin.init(ctx);
+            }
+        }
+    }
+
+    // Delegate to internal objects
+    private MBeanPluginContext createMBeanPluginContext() {
+        return new MBeanPluginContext() {
+            public ObjectName registerMBean(Object pMBean, String... pOptionalName) throws MalformedObjectNameException, NotCompliantMBeanException, InstanceAlreadyExistsException {
+                return MBeanServerHandler.this.registerMBean(pMBean,pOptionalName);
+            }
+
+            public void each(ObjectName pObjectName, MBeanEachCallback pCallback) throws IOException, ReflectionException, MBeanException {
+                mBeanServerManager.each(pObjectName,pCallback);
+            }
+
+            public <R> R call(ObjectName pObjectName, MBeanAction<R> pMBeanAction, Object... pExtraArgs) throws IOException, ReflectionException, MBeanException, AttributeNotFoundException, InstanceNotFoundException {
+                return mBeanServerManager.call(pObjectName,pMBeanAction,pExtraArgs);
+            }
+
+            public Set<ObjectName> queryNames(ObjectName pObjectName) throws IOException {
+                return mBeanServerManager.queryNames(pObjectName);
+            }
+
+            public boolean hasMBeansListChangedSince(long pTimestamp) {
+                return mBeanServerManager.hasMBeansListChangedSince(pTimestamp);
+            }
+        };
+    }
+
+
     /**
      * Initialize the server handle.
      * @param pConfig configuration passed through to the server detectors
@@ -124,7 +163,7 @@ public final ObjectName registerMBean(Object pMBean,String ... pOptionalName)
                 return registeredName;
             } catch (RuntimeException exp) {
                 throw new IllegalStateException("Could not register " + pMBean + ": " + exp, exp);
-                } catch (MBeanRegistrationException exp) {
+            } catch (MBeanRegistrationException exp) {
                 throw new IllegalStateException("Could not register " + pMBean + ": " + exp, exp);
             }
         }
@@ -166,7 +205,7 @@ public final void destroy() throws JMException {
         }
 
         // Unregister any notification listener
-        mBeanServerManager.destroy();
+        mBeanServerManager.unregisterFromMBeanNotifications();
     }
 
     /**
@@ -219,6 +258,10 @@ private List<ServerDetector> lookupDetectors() {
         return detectors;
     }
 
+    private List<MBeanPlugin> lookupMBeanPlugins() {
+        return ServiceObjectFactory.createServiceObjects("META-INF/mbean-plugins");
+    }
+
     // Detect the server by delegating it to a set of predefined detectors. These will be created
     // by a lookup mechanism, queried and thrown away after this method
     private ServerHandle detectServers(List<ServerDetector> pDetectors, LogHandler pLogHandler) {

agent/core/src/main/java/org/jolokia/backend/executor/AbstractMBeanServerExecutor.java

@@ -138,7 +138,7 @@ protected void registerForMBeanNotifications() {
     /**
      * Unregister us as listener from every registered server
      */
-    public void destroy() {
+    public void unregisterFromMBeanNotifications() {
         Set<MBeanServerConnection> servers = getMBeanServers();
         Exception lastExp = null;
         StringBuilder errors = new StringBuilder();

agent/core/src/main/java/org/jolokia/backend/executor/MBeanServerExecutor.java

@@ -79,12 +79,6 @@ <R> R call(ObjectName pObjectName, MBeanAction<R> pMBeanAction, Object... pExtra
      */
     Set<ObjectName> queryNames(ObjectName pObjectName) throws IOException;
 
-    /**
-     * Destructor method. After this method has been called, this executor is out of service and
-     * must not be used anymore
-     */
-    void destroy();
-
     /**
      * Check whether the set of MBeans in all managed MBeanServer has been changed
      * since the given time. The input is the epoch time in seconds, however, milliseconds

agent/core/src/main/java/org/jolokia/backend/plugin/MBeanPlugin.java

@@ -0,0 +1,37 @@
+package org.jolokia.backend.plugin;
+
+/*
+ * 
+ * Copyright 2014 Roland Huss
+ *
+ * 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.
+ */
+
+/**
+ * Interface describing a plugin which can be used to register extra MBeans for enhancing the Jolokia API.
+ * MBeanPlugins are looked up from the classpath and should be registered in <code>META-INF/mbean-plugins</code>
+ *
+ * @author roland
+ * @since 12/01/15
+ */
+public interface MBeanPlugin {
+
+    /**
+     * Init method for the plugin. The plugin purpose is to register MBeans and to remember the context so
+     * that it can be later used for doing JMX calls. The context should be propagated to the registered MBean so
+     * that it can be reused for JMX lookups during its operation.
+     *
+     * @param ctx the context in order to access JMX
+     */
+    void init(MBeanPluginContext ctx);
+}

agent/core/src/main/java/org/jolokia/backend/plugin/MBeanPluginContext.java

@@ -0,0 +1,46 @@
+package org.jolokia.backend.plugin;/*
+ * 
+ * Copyright 2014 Roland Huss
+ *
+ * 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.
+ */
+
+import javax.management.*;
+
+import org.jolokia.backend.executor.MBeanServerExecutor;
+
+/**
+ * A {@link MBeanPlugin}'s context for accessing JMX with all known MBeanServers. Also it allows to register
+ * on MBeans for offering own functionality.
+ *
+ * @author roland
+ * @since 12/01/15
+ */
+public interface MBeanPluginContext extends MBeanServerExecutor {
+
+    /**
+     * Register a MBean under a certain name to the platform MBeanServer. No neeed to unregister, the MBean will be
+     * automatically unregistered when shutting down the agent. It is recommended to use the domain <code>jolokia</code>
+     * and a type <code>type=plugin</code> when registering MBeans.
+     *
+     * @param pMBean MBean to register
+     * @param pOptionalName optional name under which the bean should be registered. If not provided,
+     * it depends on whether the MBean to register implements {@link javax.management.MBeanRegistration} or
+     * not.
+     *
+     * @return the name under which the MBean is registered.
+     */
+    public ObjectName registerMBean(Object pMBean,String ... pOptionalName)
+            throws MalformedObjectNameException, NotCompliantMBeanException, InstanceAlreadyExistsException;
+
+}

agent/core/src/main/java/org/jolokia/detector/ServerHandle.java

@@ -25,8 +25,9 @@
 import org.jolokia.config.Configuration;
 import org.jolokia.request.JmxRequest;
 import org.jolokia.util.LogHandler;
+import org.jolokia.util.ServiceObjectFactory;
 import org.json.simple.JSONObject;
-import org.json.simple.parser.JSONParser;
+import org.json.simple.parser.ParseException;
 
 /**
  * Information about the the server product the agent is running in.
@@ -198,14 +199,11 @@ private void addNullSafe(JSONObject pRet, String pKey, Object pValue) {
      * @return the detector specific configuration
      */
     protected JSONObject getDetectorOptions(Configuration pConfig, LogHandler pLogHandler) {
-        String optionString = pConfig.get(ConfigKey.DETECTOR_OPTIONS);
-        if (optionString != null) {
-            try {
-                JSONObject opts = (JSONObject) new JSONParser().parse(optionString);
-                return (JSONObject) opts.get(getProduct());
-            } catch (Exception e) {
-                pLogHandler.error("Could not parse options '" + optionString + "' as JSON object: " + e,e);
-            }
+        String options = pConfig.get(ConfigKey.DETECTOR_OPTIONS);
+        try {
+            return ServiceObjectFactory.extractServiceConfiguration(options,getProduct());
+        } catch (ParseException e) {
+            pLogHandler.error("Could not parse detector options '" + options + "' as JSON object: " + e,e);
         }
         return null;
     }

agent/core/src/main/java/org/jolokia/util/ServiceObjectFactory.java

@@ -20,6 +20,10 @@
 import java.net.URL;
 import java.util.*;
 
+import org.json.simple.JSONObject;
+import org.json.simple.parser.JSONParser;
+import org.json.simple.parser.ParseException;
+
 /**
  * A simple factory for creating services with no-arg constructors from a textual
  * descriptor. This descriptor, which must be a resource loadable by this class'
@@ -53,7 +57,7 @@ private ServiceObjectFactory() {}
      *        Normally, default service should be given as first parameter so that custom
      *        descriptors have a chance to remove a default service.
      * @param <T> type of the service objects to create
-     * @return a ordered list of created services.
+     * @return a ordered list of created services or an empty list.
      */
     public static <T> List<T> createServiceObjects(String... pDescriptorPaths) {
         try {
@@ -150,6 +154,22 @@ private static void closeReader(LineNumberReader pReader) {
         }
     }
 
+    /**
+     * Helper method for parsing a string as a JSON Object and returns the JSON object which is stored under a certain key
+     *
+     * @param serviceConfigString string holding the extra configuration
+     * @param key key to lookup the extra configuration
+     * @return the extra configuration or <code>null</code> if none has been given.
+     * @throws ParseException if parsing of the original string as JSON object fails.
+     */
+    public static JSONObject extractServiceConfiguration(String serviceConfigString, String key) throws ParseException {
+        if (serviceConfigString != null) {
+                JSONObject opts = (JSONObject) new JSONParser().parse(serviceConfigString);
+                return (JSONObject) opts.get(key);
+        }
+        return null;
+    }
+
     // =============================================================================
 
      static class ServiceEntry implements Comparable<ServiceEntry> {

agent/core/src/test/java/org/jolokia/backend/executor/AbstractMBeanServerExecutorTest.java

@@ -95,14 +95,14 @@ public void updateChangeTest() throws MalformedObjectNameException, NotCompliant
                 }
             }
         } finally {
-            executor.destroy();
+            executor.unregisterFromMBeanNotifications();
         }
     }
 
     @Test
     public void destroyWithoutPriorRegistration() throws NoSuchFieldException, IllegalAccessException {
         // Should always work, even when no registration has happened. Non exisiting listeners will be simplu ignored, since we didnt do any registration before
-        executor.destroy();
+        executor.unregisterFromMBeanNotifications();
     }
 
     private long currentTime() {

agent/core/src/test/java/org/jolokia/detector/ServerHandleTest.java

@@ -97,7 +97,7 @@ public void detectorOptionsEmpty() {
     @Test
     public void detectOptionsFail() {
         LogHandler handler = EasyMock.createMock(LogHandler.class);
-        handler.error(matches("^.*parse options.*"),isA(Exception.class));
+        handler.error(matches("^.*parse detector options.*"),isA(Exception.class));
         replay(handler);
 
         Configuration opts = new Configuration(ConfigKey.DETECTOR_OPTIONS,"blub: bla");

agent/core/src/test/java/org/jolokia/handler/ListHandlerTest.java

@@ -53,7 +53,7 @@ private void createHandler() {
 
     @AfterMethod
     private void destroy() {
-        executor.destroy();
+        executor.unregisterFromMBeanNotifications();
     }
 
     @Test

agent/core/src/test/java/org/jolokia/util/ServiceObjectFactoryTest.java

@@ -16,12 +16,15 @@
  * limitations under the License.
  */
 
-import org.testng.annotations.Test;
-
 import java.util.Iterator;
 import java.util.List;
 
+import org.json.simple.JSONObject;
+import org.json.simple.parser.ParseException;
+import org.testng.annotations.Test;
+
 import static org.testng.Assert.assertEquals;
+import static org.testng.Assert.assertNull;
 
 /**
  * @author roland
@@ -53,6 +56,20 @@ public void classCastException() {
         String bla = services.get(0);
     }
 
+    @Test
+    public void extractServiceConfiguration() throws ParseException {
+        String configString = "{ \"healthCheck\" : { \"path\": \"/tmp\"}}";
+        JSONObject extra =
+                ServiceObjectFactory.extractServiceConfiguration(configString, "healthCheck");
+        assertEquals("/tmp",extra.get("path"));
+        assertEquals(extra.size(),1);
+        assertNull(ServiceObjectFactory.extractServiceConfiguration(configString,"blub"));
+    }
+
+    @Test(expectedExceptions = ParseException.class)
+    public void extractServiceConfigurationFailed() throws ParseException {
+                ServiceObjectFactory.extractServiceConfiguration("{{ blub }", "healthCheck");
+    }
 
     interface TestService { String getName(); }
     public static class Test1 implements TestService { public String getName() { return "one"; } }