gnu.cajo.utils.extra

Class AuditorItem

java.lang.Object

gnu.cajo.utils.extra.AuditorItem

All Implemented Interfaces:

Invoke, Serializable

public class AuditorItem
extends Object
implements Invoke

This class is used to transparently pre and post-pend audit functionality to any given object reference. It is typically used to check the integrity of the invocation arguments, or the authenticity of the invoking object. Likewise, it can review the invocation results, to augment, or delete certain components. The wrapped object is unaware, and need not be changed, to assist in this functionality. It can be used on local objects, for which the code is available, as easily as on remote object references, for which no code is available. It is ideal for use in debug, and development activities, as well as for security, in production environments. The technique is essentially an implementation of the Decorator design pattern.

Version:

1.0, 19-Sep-04 Initial release

Author:

John Catherino

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
Object	auditor The auditor object.
Object	item This is the object to be audited.

Constructor Summary

Constructors

Constructor and Description
AuditorItem(Object item, Object auditor) This creates the object, to audit the target object's use.

Method Summary

Methods

Modifier and Type	Method and Description
Object	invoke(String method, Object args) This method audits the incoming calls.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

auditor

public final Object auditor

The auditor object. This object's preprocess method will be invoked with the arguments to be provided to the audited object. It has the three options:

• Change the arguments
• Approve the arguments, as is
• Reject the invocation, by throwing an Exception.

The arguments the preprocess method returns will then be passed on to the audited item for processing. The result of this operation will be passed to the auditing item's postprocess method. Again, it has the similiar three options; to change, approve, or reject the returned data. It is declared as public to allow the reference of the AuditorItem, and its auditor object, from a single instance of AuditorItem.

item

public final Object item

This is the object to be audited. Since it has no knowlege of the audit it's structure need not be changed in any way to accomodate it. It is declared as public to allow the reference of the AuditorItem, and its wrapped object, from a single instance of AuditorItem.

Constructor Detail

AuditorItem

public AuditorItem(Object item,
           Object auditor)

This creates the object, to audit the target object's use. The class in not declared final, to allow no-arg auditing items to be easily created.

Parameters:

item - The object to receive the client invocation. It can be local, remote, or even a proxy.

auditor - The object to receive the calls prior to, and following the audited item's operation. It can be local, remote, or even a proxy.

Method Detail

invoke

public Object invoke(String method,
            Object args)
              throws Exception

This method audits the incoming calls. If the auditor approves, or change the supplied arguments, they will be passed into the audited item for processing. The auditor will again review the returned data, or exception, and will likewise approve or change it. Note: this method can be called reentrantly. Also, if the audited item invocation results in an exception, and the auditor approves, it can simply return the exception, and the wrapper will throw it automatically.

Specified by:

invoke in interface Invoke

Parameters:

method - The internal object's public method being called.

args - The arguments to pass to the internal object's method.

Returns:

The sychronous audited data, if any, resulting from the invocation.

Throws:

RemoteException - For a network related failure.

NoSuchMethodException - If the method/agruments signature cannot be matched to the internal object's public method interface.

Exception - If the internal object's method rejects the invocation, or if it has been rejected by the auditor object.