/*
* Copyright (c) 1999, 2004, 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
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*/
package javax.management;
// RI import
import javax.management.MBeanServer;
/**
* Represents attributes used as arguments to relational constraints.
* 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;
/**
* @serial The name of the attribute
*/
private String attr;
/**
* 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 <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.
*
* @return the attribute name.
*/
public String getAttributeName() {
return attr;
}
/**
* Applies the <CODE>AttributeValueExp</CODE> on an MBean.
*
* @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
*
*/
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.
*/
public String toString() {
return attr;
}
/**
* 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.
*/
/* 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. */
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.
*
* @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;
}
}
}