/*
 * Copyright 2002,2004-2005 The Apache Software Foundation.
 * 
 * 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.apache.catalina.ant.jmx;


import javax.management.MBeanServerConnection;
import javax.management.ObjectName;

import org.apache.tools.ant.BuildException;


/**
 * Access <em>JMX</em> JSR 160 MBeans Server. 
 * <ul>
 * <li>Get Mbeans attributes</li>
 * <li>Show Get result as Ant console log</li>
 * <li>Bind Get result as Ant properties</li>
 * </ul>
 * <p>
 * Examples:
 * <br/>
 * Get a Mbean IDataSender attribute nrOfRequests and create a new ant property <em>IDataSender.9025.nrOfRequests</em> 
 * <pre>
 *   &lt;jmx:get
 *           ref="jmx.server"
 *           name="Catalina:type=IDataSender,host=localhost,senderAddress=192.168.1.2,senderPort=9025" 
 *           attribute="nrOfRequests"
 *           resultproperty="IDataSender.9025.nrOfRequests"
 *           echo="false"&gt;
 *       /&gt;
 * </pre>
 * </p>
 * <p>
 * First call to a remote MBeanserver save the JMXConnection a referenz <em>jmx.server</em>
 * </p>
 * These tasks require Ant 1.6 or later interface.
 *
 * @author Peter Rossbach
 * @version $Revision$ $Date$
 * @since 5.5.10
 */

public class JMXAccessorGetTask extends JMXAccessorTask {


    // ----------------------------------------------------- Instance Variables

    private String attribute;

    // ----------------------------------------------------- Instance Info

    /**
     * Descriptive information describing this implementation.
     */
    private static final String info = "org.apache.catalina.ant.JMXAccessorGetTask/1.0";

    /**
     * Return descriptive information about this implementation and the
     * corresponding version number, in the format
     * <code>&lt;description&gt;/&lt;version&gt;</code>.
     */
    public String getInfo() {

        return (info);

    }

    // ------------------------------------------------------------- Properties
    
    /**
     * @return Returns the attribute.
     */
    public String getAttribute() {
        return attribute;
    }
    
    /**
     * @param attribute The attribute to set.
     */
    public void setAttribute(String attribute) {
        this.attribute = attribute;
    }
    
  
    // ------------------------------------------------------ protected Methods
    
    /**
     * Execute the specified command, based on the configured properties. The
     * input stream will be closed upon completion of this task, whether it was
     * executed successfully or not.
     * 
     * @exception BuildException
     *                if an error occurs
     */
    public String jmxExecute(MBeanServerConnection jmxServerConnection)
        throws Exception {

        if (getName() == null) {
            throw new BuildException("Must specify a 'name'");
        }
        if ((attribute == null)) {
            throw new BuildException(
                    "Must specify a 'attribute' for get");
        }
        return  jmxGet(jmxServerConnection, getName());
     }


    /**
     * @param jmxServerConnection
     * @param name
     * @return The value of the given named attribute
     * @throws Exception
     */
    protected String jmxGet(MBeanServerConnection jmxServerConnection,String name) throws Exception {
        String error = null;
        if(isEcho()) {
            handleOutput("MBean " + name + " get attribute " + attribute );
        }
        Object result = jmxServerConnection.getAttribute(
                new ObjectName(name), attribute);
        if (result != null) {
            echoResult(attribute,result);
            createProperty(result);
        } else
            error = "Attribute " + attribute + " is empty";
        return error;
    }
}