TransparentWrapper.java
/*
** Module : TransparentWrapper.java
** Abstract : simple container that implements WrappedResource for any object
**
** Copyright (c) 2007-2020, Golden Code Development Corporation.
**
** -#- -I- --Date-- --JPRM-- --------------------------Description---------------------------
** 001 GES 20070221 @32199 Created initial version which represents a
** simple container that implements
** WrappedResource for any object.
** 002 CA 20090227 @41382 Added WrappedResources.isUnknown method; this
** implementation returns false, if referent is
** not an instance of WrappedResource; else,
** it returns referent.isUnknown() value.
** 003 CA 20130112 Made the referent field protected. Fixed equals.
** 004 OM 20130304 Refactored isValid and isUnknown of WrappedResource to valid
** and unknown.
** 005 CA 20150502 The resource ID needs to be kept at the resource, so it can be
** accessed after the resource is deleted.
** 006 CA 20200514 Fixed equals() and hashCode() when there is no referent.
*/
/*
** This program is free software: you can redistribute it and/or modify
** it under the terms of the GNU Affero General Public License as
** published by the Free Software Foundation, either version 3 of the
** License, or (at your option) any later version.
**
** This program 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 Affero General Public License for more details.
**
** You may find a copy of the GNU Affero GPL version 3 at the following
** location: https://www.gnu.org/licenses/agpl-3.0.en.html
**
** Additional terms under GNU Affero GPL version 3 section 7:
**
** Under Section 7 of the GNU Affero GPL version 3, the following additional
** terms apply to the works covered under the License. These additional terms
** are non-permissive additional terms allowed under Section 7 of the GNU
** Affero GPL version 3 and may not be removed by you.
**
** 0. Attribution Requirement.
**
** You must preserve all legal notices or author attributions in the covered
** work or Appropriate Legal Notices displayed by works containing the covered
** work. You may not remove from the covered work any author or developer
** credit already included within the covered work.
**
** 1. No License To Use Trademarks.
**
** This license does not grant any license or rights to use the trademarks
** Golden Code, FWD, any Golden Code or FWD logo, or any other trademarks
** of Golden Code Development Corporation. You are not authorized to use the
** name Golden Code, FWD, or the names of any author or contributor, for
** publicity purposes without written authorization.
**
** 2. No Misrepresentation of Affiliation.
**
** You may not represent yourself as Golden Code Development Corporation or FWD.
**
** You may not represent yourself for publicity purposes as associated with
** Golden Code Development Corporation, FWD, or any author or contributor to
** the covered work, without written authorization.
**
** 3. No Misrepresentation of Source or Origin.
**
** You may not represent the covered work as solely your work. All modified
** versions of the covered work must be marked in a reasonable way to make it
** clear that the modified work is not originating from Golden Code Development
** Corporation or FWD. All modified versions must contain the notices of
** attribution required in this license.
*/
package com.goldencode.p2j.util;
/**
* Simple container that stores an object instance and implements the
* {@link WrappedResource} interface. Since {@link #hashCode} and
* {@link #equals} are redirected to the contained reference, this is as
* suitable for use in a collection as the contained reference.
*/
public class TransparentWrapper
implements WrappedResource
{
/** The object being contained. */
protected Object referent = null;
/**
* The resource's ID. Remains <code>null</code> until the ID is requested via
* {@link handle#resourceId}
*/
private Long id = null;
/**
* Construct an instance given the object reference to contain.
*
* @param referent
* The object to contain.
*/
public TransparentWrapper(Object referent)
{
this.referent = referent;
}
/**
* Get this resource's ID, if is already set.
*
* @return The resource's ID or <code>null</code> if not set.
*/
@Override
public Long id()
{
return id;
}
/**
* Set this resource's ID.
*
* @param id
* The resource's ID.
*/
@Override
public void id(long id)
{
this.id = id;
}
/**
* Returns the referent of this instance as an <code>Object</code>.
*
* @return The value as an <code>Object</code> or <code>null</code> if
* there is no contained object.
*/
public Object get()
{
return referent;
}
/**
* Set the referent of this instance.
*
* @param referent
* The value to be represented in this instance.
*/
public void set(Object referent)
{
this.referent = referent;
}
/**
* Reports if this object is valid for use. If the contained object
* reference itself implements {@link WrappedResource}, then this
* call will be redirected to the contained object. Otherwise, if
* the contained object is <code>null</code>, then it is considered
* invalid and not <code>null</code> is valid.
*
* @return <code>true</code> if we are valid (can be used).
*/
public boolean valid()
{
if (referent != null && referent instanceof WrappedResource)
{
// pass through the validity check
WrappedResource res = (WrappedResource) referent;
return res.valid();
}
// otherwise non-null means valid
return (referent != null);
}
/**
* Reports if this object is unknown.<p>
* If {@link #referent} is not an instance of {@link WrappedResource}, it
* returns false. Else, it returns {@link WrappedResource#unknown()}
* result.
*
* @return <code>true</code> if object is unknown.
*/
public boolean unknown()
{
if (referent != null && referent instanceof WrappedResource)
{
WrappedResource res = (WrappedResource) referent;
return res.unknown();
}
return false;
}
/**
* Hash code implementation which is redirected to that of the
* contained object so long as that object is not <code>null</code>.
*
* @return Hash code value for this object instance.
*/
public int hashCode()
{
return referent == null ? super.hashCode() : referent.hashCode();
}
/**
* Determines if this instance and the passed-in instance are equivalent.
*
* @param obj
* The instance to compare against.
*
* @return <code>true</code> if the objects are the same.
*/
public boolean equals(Object obj)
{
if (obj != null && obj instanceof TransparentWrapper)
{
obj = ((TransparentWrapper) obj).referent;
}
return (referent == null) ? super.equals(obj) : referent.equals(obj);
}
}