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/*
 * Copyright 2012-2015 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 net.nicoll.boot.daemon;

import java.io.IOException;

import javax.management.AttributeNotFoundException;
import javax.management.InstanceNotFoundException;
import javax.management.MBeanException;
import javax.management.MBeanServerConnection;
import javax.management.MalformedObjectNameException;
import javax.management.ObjectName;
import javax.management.ReflectionException;
import javax.management.remote.JMXConnector;
import javax.management.remote.JMXConnectorFactory;
import javax.management.remote.JMXServiceURL;

import org.springframework.jmx.JmxException;

/**
 * A JMX client for the {@code SpringApplicationAdmin} MBean. Permits to obtain
 * information about a given Spring application.
 *
 * @author Stephane Nicoll
 */
class SpringApplicationAdminClient {

    // Note: see SpringApplicationAdminJmxAutoConfiguration
    static final String DEFAULT_OBJECT_NAME
            = "org.springframework.boot:type=Admin,name=SpringApplication";

    private final MBeanServerConnection connection;

    private final ObjectName objectName;

    SpringApplicationAdminClient(
            final MBeanServerConnection connection, final String jmxName) {
        this.connection = connection;
        this.objectName = toObjectName(jmxName);
    }

    /**
     * Check if the spring application managed by this instance is ready.
     * Returns {@code false} if the mbean is not yet deployed so this method
     * should be repeatedly called until a timeout is reached.
     *
     * @return {@code true} if the application is ready to service requests
     *
     * @throws org.springframework.jmx.JmxException if the JMX service could not
     *                                              be contacted
     */
    public boolean isReady() {
        try {
            return (Boolean) this.connection.getAttribute(this.objectName,
                    "Ready");
        } catch (InstanceNotFoundException ex) {
            return false; // Instance not available yet
        } catch (AttributeNotFoundException ex) {
            throw new IllegalStateException(
                    "Unexpected: attribute 'Ready' not available", ex);
        } catch (ReflectionException ex) {
            throw new JmxException("Failed to retrieve Ready attribute",
                    ex.getCause());
        } catch (MBeanException | IOException ex) {
            throw new JmxException(ex.getMessage(), ex);
        }
    }

    /**
     * Stop the application managed by this instance.
     *
     * @throws JmxException              if the JMX service could not be
     *                                   contacted
     * @throws IOException               if an I/O error occurs
     * @throws InstanceNotFoundException if the lifecycle mbean cannot be found
     */
    void stop() throws IOException, InstanceNotFoundException {
        try {
            this.connection.invoke(this.objectName, "shutdown", null, null);
        } catch (ReflectionException ex) {
            throw new JmxException("Shutdown failed", ex.getCause());
        } catch (MBeanException ex) {
            throw new JmxException("Could not invoke shutdown operation", ex);
        }
    }

    private ObjectName toObjectName(final String name) {
        try {
            return new ObjectName(name);
        } catch (MalformedObjectNameException ex) {
            throw new IllegalArgumentException(
                    "Invalid jmx name '" + name + "'");
        }
    }

    /**
     * Create a connector for an {@link javax.management.MBeanServer} exposed on
     * the current machine and the current port. Security should be disabled.
     *
     * @param port the port on which the mbean server is exposed
     *
     * @return a connection
     *
     * @throws IOException if the connection to that server failed
     */
    static JMXConnector connect(final int port) throws IOException {
        String url = "service:jmx:rmi:///jndi/rmi://127.0.0.1:" + port
                + "/jmxrmi";
        JMXServiceURL serviceUrl = new JMXServiceURL(url);
        return JMXConnectorFactory.connect(serviceUrl, null);
    }

}