/*
* Copyright 2002-2016 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.jmx.support;
import java.util.LinkedHashSet;
import java.util.Set;
import javax.management.InstanceAlreadyExistsException;
import javax.management.InstanceNotFoundException;
import javax.management.JMException;
import javax.management.MBeanServer;
import javax.management.ObjectInstance;
import javax.management.ObjectName;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.core.Constants;
import org.springframework.util.Assert;
/**
* Provides supporting infrastructure for registering MBeans with an
* {@link javax.management.MBeanServer}. The behavior when encountering
* an existing MBean at a given {@link ObjectName} is fully configurable
* allowing for flexible registration settings.
*
* <p>All registered MBeans are tracked and can be unregistered by calling
* the #{@link #unregisterBeans()} method.
*
* <p>Sub-classes can receive notifications when an MBean is registered or
* unregistered by overriding the {@link #onRegister(ObjectName)} and
* {@link #onUnregister(ObjectName)} methods respectively.
*
* <p>By default, the registration process will fail if attempting to
* register an MBean using a {@link javax.management.ObjectName} that is
* already used.
*
* <p>By setting the {@link #setRegistrationPolicy(RegistrationPolicy) registrationPolicy}
* property to {@link RegistrationPolicy#IGNORE_EXISTING} the registration process
* will simply ignore existing MBeans leaving them registered. This is useful in settings
* where multiple applications want to share a common MBean in a shared {@link MBeanServer}.
*
* <p>Setting {@link #setRegistrationPolicy(RegistrationPolicy) registrationPolicy} property
* to {@link RegistrationPolicy#REPLACE_EXISTING} will cause existing MBeans to be replaced
* during registration if necessary. This is useful in situations where you can't guarantee
* the state of your {@link MBeanServer}.
*
* @author Rob Harrop
* @author Juergen Hoeller
* @author Phillip Webb
* @since 2.0
* @see #setServer
* @see #setRegistrationPolicy
* @see org.springframework.jmx.export.MBeanExporter
*/
public class MBeanRegistrationSupport {
/**
* {@code Log} instance for this class.
*/
protected final Log logger = LogFactory.getLog(getClass());
/**
* The {@code MBeanServer} instance being used to register beans.
*/
protected MBeanServer server;
/**
* The beans that have been registered by this exporter.
*/
private final Set<ObjectName> registeredBeans = new LinkedHashSet<>();
/**
* The policy used when registering an MBean and finding that it already exists.
* By default an exception is raised.
*/
private RegistrationPolicy registrationPolicy = RegistrationPolicy.FAIL_ON_EXISTING;
/**
* Specify the {@code MBeanServer} instance with which all beans should
* be registered. The {@code MBeanExporter} will attempt to locate an
* existing {@code MBeanServer} if none is supplied.
*/
public void setServer(MBeanServer server) {
this.server = server;
}
/**
* Return the {@code MBeanServer} that the beans will be registered with.
*/
public final MBeanServer getServer() {
return this.server;
}
/**
* The policy to use when attempting to register an MBean
* under an {@link javax.management.ObjectName} that already exists.
* @param registrationPolicy the policy to use
* @since 3.2
*/
public void setRegistrationPolicy(RegistrationPolicy registrationPolicy) {
Assert.notNull(registrationPolicy, "RegistrationPolicy must not be null");
this.registrationPolicy = registrationPolicy;
}
/**
* Actually register the MBean with the server. The behavior when encountering
* an existing MBean can be configured using {@link #setRegistrationPolicy}.
* @param mbean the MBean instance
* @param objectName the suggested ObjectName for the MBean
* @throws JMException if the registration failed
*/
protected void doRegister(Object mbean, ObjectName objectName) throws JMException {
ObjectName actualObjectName;
synchronized (this.registeredBeans) {
ObjectInstance registeredBean = null;
try {
registeredBean = this.server.registerMBean(mbean, objectName);
}
catch (InstanceAlreadyExistsException ex) {
if (this.registrationPolicy == RegistrationPolicy.IGNORE_EXISTING) {
if (logger.isDebugEnabled()) {
logger.debug("Ignoring existing MBean at [" + objectName + "]");
}
}
else if (this.registrationPolicy == RegistrationPolicy.REPLACE_EXISTING) {
try {
if (logger.isDebugEnabled()) {
logger.debug("Replacing existing MBean at [" + objectName + "]");
}
this.server.unregisterMBean(objectName);
registeredBean = this.server.registerMBean(mbean, objectName);
}
catch (InstanceNotFoundException ex2) {
logger.error("Unable to replace existing MBean at [" + objectName + "]", ex2);
throw ex;
}
}
else {
throw ex;
}
}
// Track registration and notify listeners.
actualObjectName = (registeredBean != null ? registeredBean.getObjectName() : null);
if (actualObjectName == null) {
actualObjectName = objectName;
}
this.registeredBeans.add(actualObjectName);
}
onRegister(actualObjectName, mbean);
}
/**
* Unregisters all beans that have been registered by an instance of this class.
*/
protected void unregisterBeans() {
Set<ObjectName> snapshot;
synchronized (this.registeredBeans) {
snapshot = new LinkedHashSet<>(this.registeredBeans);
}
if (!snapshot.isEmpty()) {
logger.info("Unregistering JMX-exposed beans");
}
for (ObjectName objectName : snapshot) {
doUnregister(objectName);
}
}
/**
* Actually unregister the specified MBean from the server.
* @param objectName the suggested ObjectName for the MBean
*/
protected void doUnregister(ObjectName objectName) {
boolean actuallyUnregistered = false;
synchronized (this.registeredBeans) {
if (this.registeredBeans.remove(objectName)) {
try {
// MBean might already have been unregistered by an external process
if (this.server.isRegistered(objectName)) {
this.server.unregisterMBean(objectName);
actuallyUnregistered = true;
}
else {
if (logger.isWarnEnabled()) {
logger.warn("Could not unregister MBean [" + objectName + "] as said MBean " +
"is not registered (perhaps already unregistered by an external process)");
}
}
}
catch (JMException ex) {
if (logger.isErrorEnabled()) {
logger.error("Could not unregister MBean [" + objectName + "]", ex);
}
}
}
}
if (actuallyUnregistered) {
onUnregister(objectName);
}
}
/**
* Return the {@link ObjectName ObjectNames} of all registered beans.
*/
protected final ObjectName[] getRegisteredObjectNames() {
synchronized (this.registeredBeans) {
return this.registeredBeans.toArray(new ObjectName[this.registeredBeans.size()]);
}
}
/**
* Called when an MBean is registered under the given {@link ObjectName}. Allows
* subclasses to perform additional processing when an MBean is registered.
* <p>The default implementation delegates to {@link #onRegister(ObjectName)}.
* @param objectName the actual {@link ObjectName} that the MBean was registered with
* @param mbean the registered MBean instance
*/
protected void onRegister(ObjectName objectName, Object mbean) {
onRegister(objectName);
}
/**
* Called when an MBean is registered under the given {@link ObjectName}. Allows
* subclasses to perform additional processing when an MBean is registered.
* <p>The default implementation is empty. Can be overridden in subclasses.
* @param objectName the actual {@link ObjectName} that the MBean was registered with
*/
protected void onRegister(ObjectName objectName) {
}
/**
* Called when an MBean is unregistered under the given {@link ObjectName}. Allows
* subclasses to perform additional processing when an MBean is unregistered.
* <p>The default implementation is empty. Can be overridden in subclasses.
* @param objectName the {@link ObjectName} that the MBean was registered with
*/
protected void onUnregister(ObjectName objectName) {
}
}