https://openjdk.java.net/ 
/*
 * Copyright (c) 1999, 2008, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package javax.management;


import com.sun.jmx.mbeanserver.Introspector;
import java.io.IOException;
import java.io.ObjectInputStream;


Represents attributes used as arguments to relational constraints. Instances of this class are usually obtained using 
Query.attr.


An AttributeValueExp may be used anywhere a
ValueExp is required.

Since:1.5
/**
 * <p>Represents attributes used as arguments to relational constraints.
 * Instances of this class are usually obtained using {@link Query#attr(String)
 * Query.attr}.</p>
 *
 * <p>An <CODE>AttributeValueExp</CODE> may be used anywhere a
 * <CODE>ValueExp</CODE> is required.
 *
 * @since 1.5
 */
public class AttributeValueExp implements ValueExp  {


    /* Serial version */
    private static final long serialVersionUID = -7768025046539163385L;

    
@serialThe name of the attribute
/**
     * @serial The name of the attribute
     */
    private String attr;

    
An AttributeValueExp with a null attribute.

Deprecated:An instance created with this constructor cannot be
used in a query.
/**
     * An <code>AttributeValueExp</code> with a null attribute.
     * @deprecated An instance created with this constructor cannot be
     * used in a query.
     */
    @Deprecated
    public AttributeValueExp() {
    }

    
Creates a new AttributeValueExp representing the
specified object attribute, named attr.

Params:
  • attr – the name of the attribute whose value is the value of this ValueExp.
/**
     * Creates a new <CODE>AttributeValueExp</CODE> representing the
     * specified object attribute, named attr.
     *
     * @param attr the name of the attribute whose value is the value
     * of this {@link ValueExp}.
     */
    public AttributeValueExp(String attr) {
        this.attr = attr;
    }

    
Returns a string representation of the name of the attribute.

Returns:the attribute name.
/**
     * Returns a string representation of the name of the attribute.
     *
     * @return the attribute name.
     */
    public String getAttributeName()  {
        return attr;
    }

    
Applies the AttributeValueExp on an MBean. This method calls getAttribute(name) and wraps the result as a ValueExp. The value returned by getAttribute must be a Number, String, or Boolean; otherwise this method throws a BadAttributeValueExpException, which will cause the containing query to be false for this name.


Params:
  • name – The name of the MBean on which the AttributeValueExp will be applied.
Throws:
Returns: The ValueExp.
/**
     * <p>Applies the <CODE>AttributeValueExp</CODE> on an MBean.
     * This method calls {@link #getAttribute getAttribute(name)} and wraps
     * the result as a {@code ValueExp}.  The value returned by
     * {@code getAttribute} must be a {@code Number}, {@code String},
     * or {@code Boolean}; otherwise this method throws a
     * {@code BadAttributeValueExpException}, which will cause
     * the containing query to be false for this {@code name}.</p>
     *
     * @param name The name of the MBean on which the <CODE>AttributeValueExp</CODE> will be applied.
     *
     * @return  The <CODE>ValueExp</CODE>.
     *
     * @exception BadAttributeValueExpException
     * @exception InvalidApplicationException
     * @exception BadStringOperationException
     * @exception BadBinaryOpValueExpException
     *
     */
    @Override
    public ValueExp apply(ObjectName name) throws BadStringOperationException, BadBinaryOpValueExpException,
        BadAttributeValueExpException, InvalidApplicationException {
        Object result = getAttribute(name);

        if (result instanceof Number) {
            return new NumericValueExp((Number)result);
        } else if (result instanceof String) {
            return new StringValueExp((String)result);
        } else if (result instanceof Boolean) {
            return new BooleanValueExp((Boolean)result);
        } else {
            throw new BadAttributeValueExpException(result);
        }
    }

    
Returns the string representing its value.

/**
     * Returns the string representing its value.
     */
    @Override
    public String toString()  {
        return attr;
    }


    
Sets the MBean server on which the query is to be performed.

Params:
  • s – The MBean server on which the query is to be performed.
Deprecated:This method has no effect. The MBean Server used to obtain an attribute value is QueryEval.getMBeanServer().
/**
     * Sets the MBean server on which the query is to be performed.
     *
     * @param s The MBean server on which the query is to be performed.
     *
     * @deprecated This method has no effect.  The MBean Server used to
     * obtain an attribute value is {@link QueryEval#getMBeanServer()}.
     */
    /* There is no need for this method, because if a query is being
       evaluted an AttributeValueExp can only appear inside a QueryExp,
       and that QueryExp will itself have done setMBeanServer.  */
    @Deprecated
    @Override
    public void setMBeanServer(MBeanServer s)  {
    }


    
Return the value of the given attribute in the named MBean.
If the attempt to access the attribute generates an exception,
return null.


The MBean Server used is the one returned by QueryEval.getMBeanServer().


Params:
  • name – the name of the MBean whose attribute is to be returned.
Returns:the value of the attribute, or null if it could not be
obtained.
/**
     * <p>Return the value of the given attribute in the named MBean.
     * If the attempt to access the attribute generates an exception,
     * return null.</p>
     *
     * <p>The MBean Server used is the one returned by {@link
     * QueryEval#getMBeanServer()}.</p>
     *
     * @param name the name of the MBean whose attribute is to be returned.
     *
     * @return the value of the attribute, or null if it could not be
     * obtained.
     */
    protected Object getAttribute(ObjectName name) {
        try {
            // Get the value from the MBeanServer

            MBeanServer server = QueryEval.getMBeanServer();

            return server.getAttribute(name, attr);
        } catch (Exception re) {
            return null;
        }
    }
}