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/*
* Copyright 2015-2024 Open Text.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.github.cafapi.common.util.ref;
import java.util.Objects;
/**
* Utility wrapper for allowing data to potentially be within a message or located on a remote DataStore. The acquire(ObjectSource) method
* allows transparent method of obtaining the wrapped data, which will only be retrieved the first time acquire is called (if it is not
* already present).
*
* It should be noted that because this class returns a fully formed Java object instance, the entire instance must be loaded into memory.
* As such, this wrapper should only be used for objects that are at most a few megabytes of data.
*
* @param the type of the wrapped, referenced object
*/
public final class ReferencedObject
{
private T object;
private String reference;
private Class objectClass;
// for deserialisation
ReferencedObject()
{
}
/**
* Create a new Referenced object.
*
* @param objectClass the class of the object being referenced
* @param ref the optional reference to be interpreted which points to the object
* @param obj the optional actual object itself
*/
ReferencedObject(final Class objectClass, final String ref, final T obj)
{
this.objectClass = Objects.requireNonNull(objectClass);
this.reference = ref;
this.object = obj;
}
/**
* Return the referenced object, potentially performing a remote DataStore lookup and deserialisation. If the object is already
* present or has been previously acquired, it is immediately returned.
*
* @param source the implementation that provides object instances given the provided references
* @return the object that this container is wrapping
* @throws DataSourceException if the object cannot be acquired
* @throws IllegalStateException if there is no object or reference present
*/
public synchronized T acquire(final DataSource source)
throws DataSourceException
{
if (object == null) {
if (getReference() == null) {
throw new IllegalStateException("No reference or object present");
} else {
object = source.getObject(getReference(), objectClass);
}
}
return object;
}
/**
* @return the remote reference to the object in the DataStore, if set
*/
public String getReference()
{
return reference;
}
/**
* Create a ReferencedObject that uses a remote reference to data present in an ObjectSource.
*
* @param clazz the class of the referenced object
* @param ref the reference to be interpreted by the DataStore
* @param the type of the referenced object
* @return a new ReferencedObject instance that relates to a remote object via reference
*/
public static ReferencedObject getReferencedObject(final Class clazz, final String ref)
{
return new ReferencedObject<>(clazz, ref, null);
}
/**
* Create a ReferencedObject that directly wraps an object without a reference.
*
* @param clazz the class of the object
* @param obj the object to wrapper
* @param the type of the object
* @return a new ReferencedObject instance that directly wraps the object specified
*/
public static ReferencedObject getWrappedObject(final Class clazz, final T obj)
{
return new ReferencedObject<>(clazz, null, obj);
}
}