/*
 * Copyright 2002-2019 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
 *
 *      https://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 javax.management.MBeanServer;
import javax.management.MBeanServerFactory;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.jmx.MBeanServerNotFoundException;
import org.springframework.lang.Nullable;

/**
 * {@link FactoryBean} that obtains a {@link javax.management.MBeanServer} reference
 * through the standard JMX 1.2 {@link javax.management.MBeanServerFactory}
 * API.
 *
 * <p>Exposes the {@code MBeanServer} for bean references.
 *
 * <p>By default, {@code MBeanServerFactoryBean} will always create
 * a new {@code MBeanServer} even if one is already running. To have
 * the {@code MBeanServerFactoryBean} attempt to locate a running
 * {@code MBeanServer} first, set the value of the
 * "locateExistingServerIfPossible" property to "true".
 *
 * @author Rob Harrop
 * @author Juergen Hoeller
 * @since 1.2
 * @see #setLocateExistingServerIfPossible
 * @see #locateMBeanServer
 * @see javax.management.MBeanServer
 * @see javax.management.MBeanServerFactory#findMBeanServer
 * @see javax.management.MBeanServerFactory#createMBeanServer
 * @see javax.management.MBeanServerFactory#newMBeanServer
 * @see MBeanServerConnectionFactoryBean
 * @see ConnectorServerFactoryBean
 */
public class MBeanServerFactoryBean implements FactoryBean<MBeanServer>, InitializingBean, DisposableBean {

        protected final Log logger = LogFactory.getLog(getClass());

        private boolean locateExistingServerIfPossible = false;

        @Nullable
        private String agentId;

        @Nullable
        private String defaultDomain;

        private boolean registerWithFactory = true;

        @Nullable
        private MBeanServer server;

        private boolean newlyRegistered = false;


        /**
         * Set whether or not the {@code MBeanServerFactoryBean} should attempt
         * to locate a running {@code MBeanServer} before creating one.
         * <p>Default is {@code false}.
         */
        public void setLocateExistingServerIfPossible(boolean locateExistingServerIfPossible) {
                this.locateExistingServerIfPossible = locateExistingServerIfPossible;
        }

        /**
         * Set the agent id of the {@code MBeanServer} to locate.
         * <p>Default is none. If specified, this will result in an
         * automatic attempt being made to locate the attendant MBeanServer,
         * and (importantly) if said MBeanServer cannot be located no
         * attempt will be made to create a new MBeanServer (and an
         * MBeanServerNotFoundException will be thrown at resolution time).
         * <p>Specifying the empty String indicates the platform MBeanServer.
         * @see javax.management.MBeanServerFactory#findMBeanServer(String)
         */
        public void setAgentId(String agentId) {
                this.agentId = agentId;
        }

        /**
         * Set the default domain to be used by the {@code MBeanServer},
         * to be passed to {@code MBeanServerFactory.createMBeanServer()}
         * or {@code MBeanServerFactory.findMBeanServer()}.
         * <p>Default is none.
         * @see javax.management.MBeanServerFactory#createMBeanServer(String)
         * @see javax.management.MBeanServerFactory#findMBeanServer(String)
         */
        public void setDefaultDomain(String defaultDomain) {
                this.defaultDomain = defaultDomain;
        }

        /**
         * Set whether to register the {@code MBeanServer} with the
         * {@code MBeanServerFactory}, making it available through
         * {@code MBeanServerFactory.findMBeanServer()}.
         * <p>Default is {@code true}.
         * @see javax.management.MBeanServerFactory#createMBeanServer
         * @see javax.management.MBeanServerFactory#findMBeanServer
         */
        public void setRegisterWithFactory(boolean registerWithFactory) {
                this.registerWithFactory = registerWithFactory;
        }


        /**
         * Creates the {@code MBeanServer} instance.
         */
        @Override
        public void afterPropertiesSet() throws MBeanServerNotFoundException {
                // Try to locate existing MBeanServer, if desired.
                if (this.locateExistingServerIfPossible || this.agentId != null) {
                        try {
                                this.server = locateMBeanServer(this.agentId);
                        }
                        catch (MBeanServerNotFoundException ex) {
                                // If agentId was specified, we were only supposed to locate that
                                // specific MBeanServer; so let's bail if we can't find it.
                                if (this.agentId != null) {
                                        throw ex;
                                }
                                logger.debug("No existing MBeanServer found - creating new one");
                        }
                }

                // Create a new MBeanServer and register it, if desired.
                if (this.server == null) {
                        this.server = createMBeanServer(this.defaultDomain, this.registerWithFactory);
                        this.newlyRegistered = this.registerWithFactory;
                }
        }

        /**
         * Attempt to locate an existing {@code MBeanServer}.
         * Called if {@code locateExistingServerIfPossible} is set to {@code true}.
         * <p>The default implementation attempts to find an {@code MBeanServer} using
         * a standard lookup. Subclasses may override to add additional location logic.
         * @param agentId the agent identifier of the MBeanServer to retrieve.
         * If this parameter is {@code null}, all registered MBeanServers are
         * considered.
         * @return the {@code MBeanServer} if found
         * @throws org.springframework.jmx.MBeanServerNotFoundException
         * if no {@code MBeanServer} could be found
         * @see #setLocateExistingServerIfPossible
         * @see JmxUtils#locateMBeanServer(String)
         * @see javax.management.MBeanServerFactory#findMBeanServer(String)
         */
        protected MBeanServer locateMBeanServer(@Nullable String agentId) throws MBeanServerNotFoundException {
                return JmxUtils.locateMBeanServer(agentId);
        }

        /**
         * Create a new {@code MBeanServer} instance and register it with the
         * {@code MBeanServerFactory}, if desired.
         * @param defaultDomain the default domain, or {@code null} if none
         * @param registerWithFactory whether to register the {@code MBeanServer}
         * with the {@code MBeanServerFactory}
         * @see javax.management.MBeanServerFactory#createMBeanServer
         * @see javax.management.MBeanServerFactory#newMBeanServer
         */
        protected MBeanServer createMBeanServer(@Nullable String defaultDomain, boolean registerWithFactory) {
                if (registerWithFactory) {
                        return MBeanServerFactory.createMBeanServer(defaultDomain);
                }
                else {
                        return MBeanServerFactory.newMBeanServer(defaultDomain);
                }
        }


        @Override
        @Nullable
        public MBeanServer getObject() {
                return this.server;
        }

        @Override
        public Class<? extends MBeanServer> getObjectType() {
                return (this.server != null ? this.server.getClass() : MBeanServer.class);
        }

        @Override
        public boolean isSingleton() {
                return true;
        }


        /**
         * Unregisters the {@code MBeanServer} instance, if necessary.
         */
        @Override
        public void destroy() {
                if (this.newlyRegistered) {
                        MBeanServerFactory.releaseMBeanServer(this.server);
                }
        }

}