/*
* @(#)MBeanFeatureInfo.java 1.29 06/03/15
*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package javax.management;
import java.io.IOException;
import java.io.StreamCorruptedException;
import java.io.ObjectOutputStream;
import java.io.ObjectInputStream;
import java.io.Serializable;
import javax.management.modelmbean.DescriptorSupport;
/**
* <p>Provides general information for an MBean descriptor object.
* The feature described can be an attribute, an operation, a
* parameter, or a notification. Instances of this class are
* immutable. Subclasses may be mutable but this is not
* recommended.</p>
*
* @since 1.5
*/
public class MBeanFeatureInfo implements Serializable, DescriptorRead {
/* Serial version */
static final long serialVersionUID = 3952882688968447265L;
/**
* The name of the feature. It is recommended that subclasses call
* {@link #getName} rather than reading this field, and that they
* not change it.
*
* @serial The name of the feature.
*/
protected String name;
/**
* The human-readable description of the feature. It is
* recommended that subclasses call {@link #getDescription} rather
* than reading this field, and that they not change it.
*
* @serial The human-readable description of the feature.
*/
protected String description;
/**
* @serial The Descriptor for this MBeanFeatureInfo. This field
* can be null, which is equivalent to an empty Descriptor.
*/
private transient Descriptor descriptor;
/**
* Constructs an <CODE>MBeanFeatureInfo</CODE> object. This
* constructor is equivalent to {@code MBeanFeatureInfo(name,
* description, (Descriptor) null}.
*
* @param name The name of the feature.
* @param description A human readable description of the feature.
*/
public MBeanFeatureInfo(String name, String description) {
this(name, description, null);
}
/**
* Constructs an <CODE>MBeanFeatureInfo</CODE> object.
*
* @param name The name of the feature.
* @param description A human readable description of the feature.
* @param descriptor The descriptor for the feature. This may be null
* which is equivalent to an empty descriptor.
*
* @since 1.6
*/
public MBeanFeatureInfo(String name, String description,
Descriptor descriptor) {
this.name = name;
this.description = description;
this.descriptor = descriptor;
}
/**
* Returns the name of the feature.
*
* @return the name of the feature.
*/
public String getName() {
return name;
}
/**
* Returns the human-readable description of the feature.
*
* @return the human-readable description of the feature.
*/
public String getDescription() {
return description;
}
/**
* Returns the descriptor for the feature. Changing the returned value
* will have no affect on the original descriptor.
*
* @return a descriptor that is either immutable or a copy of the original.
*
* @since 1.6
*/
public Descriptor getDescriptor() {
return (Descriptor) ImmutableDescriptor.nonNullDescriptor(descriptor).clone();
}
/**
* Compare this MBeanFeatureInfo to another.
*
* @param o the object to compare to.
*
* @return true if and only if <code>o</code> is an MBeanFeatureInfo such
* that its {@link #getName()}, {@link #getDescription()}, and
* {@link #getDescriptor()}
* values are equal (not necessarily identical) to those of this
* MBeanFeatureInfo.
*/
public boolean equals(Object o) {
if (o == this)
return true;
if (!(o instanceof MBeanFeatureInfo))
return false;
MBeanFeatureInfo p = (MBeanFeatureInfo) o;
return (p.getName().equals(getName()) &&
p.getDescription().equals(getDescription()) &&
p.getDescriptor().equals(getDescriptor()));
}
public int hashCode() {
return getName().hashCode() ^ getDescription().hashCode() ^
getDescriptor().hashCode();
}
/**
* Serializes an {@link MBeanFeatureInfo} to an {@link ObjectOutputStream}.
* @serialData
* For compatibility reasons, an object of this class is serialized as follows.
* <ul>
* The method {@link ObjectOutputStream#defaultWriteObject defaultWriteObject()}
* is called first to serialize the object except the field {@code descriptor}
* which is declared as transient. The field {@code descriptor} is serialized
* as follows:
* <ul>
* <li>If {@code descriptor} is an instance of the class
* {@link ImmutableDescriptor}, the method {@link ObjectOutputStream#write
* write(int val)} is called to write a byte with the value {@code 1},
* then the method {@link ObjectOutputStream#writeObject writeObject(Object obj)}
* is called twice to serialize the field names and the field values of the
* {@code descriptor}, respectively as a {@code String[]} and an
* {@code Object[]};</li>
* <li>Otherwise, the method {@link ObjectOutputStream#write write(int val)}
* is called to write a byte with the value {@code 0}, then the method
* {@link ObjectOutputStream#writeObject writeObject(Object obj)} is called
* to serialize directly the field {@code descriptor}.
* </ul>
* </ul>
* @since 1.6
*/
private void writeObject(ObjectOutputStream out) throws IOException {
out.defaultWriteObject();
if (descriptor != null &&
descriptor.getClass() == ImmutableDescriptor.class) {
out.write(1);
final String[] names = descriptor.getFieldNames();
out.writeObject(names);
out.writeObject(descriptor.getFieldValues(names));
} else {
out.write(0);
out.writeObject(descriptor);
}
}
/**
* Deserializes an {@link MBeanFeatureInfo} from an {@link ObjectInputStream}.
* @serialData
* For compatibility reasons, an object of this class is deserialized as follows.
* <ul>
* The method {@link ObjectInputStream#defaultReadObject defaultReadObject()}
* is called first to deserialize the object except the field
* {@code descriptor}, which is not serialized in the default way. Then the method
* {@link ObjectInputStream#read read()} is called to read a byte, the field
* {@code descriptor} is deserialized according to the value of the byte value:
* <ul>
* <li>1. The method {@link ObjectInputStream#readObject readObject()}
* is called twice to obtain the field names (a {@code String[]}) and
* the field values (a {@code Object[]}) of the {@code descriptor}.
* The two obtained values then are used to construct
* an {@link ImmutableDescriptor} instance for the field
* {@code descriptor};</li>
* <li>0. The value for the field {@code descriptor} is obtained directly
* by calling the method {@link ObjectInputStream#readObject readObject()}.
* If the obtained value is null, the field {@code descriptor} is set to
* {@link ImmutableDescriptor#EMPTY_DESCRIPTOR EMPTY_DESCRIPTOR};</li>
* <li>-1. This means that there is no byte to read and that the object is from
* an earlier version of the JMX API. The field {@code descriptor} is set
* to {@link ImmutableDescriptor#EMPTY_DESCRIPTOR EMPTY_DESCRIPTOR}</li>
* <li>Any other value. A {@link StreamCorruptedException} is thrown.</li>
* </ul>
* </ul>
* @since 1.6
*/
private void readObject(ObjectInputStream in)
throws IOException, ClassNotFoundException {
in.defaultReadObject();
switch (in.read()) {
case 1:
final String[] names = (String[])in.readObject();
if (names.length == 0) {
descriptor = ImmutableDescriptor.EMPTY_DESCRIPTOR;
} else {
final Object[] values = (Object[])in.readObject();
descriptor = new ImmutableDescriptor(names, values);
}
break;
case 0:
descriptor = (Descriptor)in.readObject();
if (descriptor == null) {
descriptor = ImmutableDescriptor.EMPTY_DESCRIPTOR;
}
break;
case -1: // from an earlier version of the JMX API
descriptor = ImmutableDescriptor.EMPTY_DESCRIPTOR;
break;
default:
throw new StreamCorruptedException("Got unexpected byte.");
}
}
}