[LANG-577] Add ObjectReference interface and two implementations

• Type: New Feature
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Fix Version/s: Review Patch
• Component/s: lang.*
• Assignee: Joerg Schaible
• Reporter: Joerg Schaible
• Created: 23/Dec/09 19:35
• Updated: 21/Oct/13 05:34

Description

In some situations it would be helpful to use a reference to an object, e.g. for parameters by reference

void doSomething(ObjectReference<String> ref) {
    ref.set("Hello");
}

or for anonymous methods

final ObjectReference<String> ref = new MemoryReference<String>();
final Runnable r = new Runnable() {
    void run() {
        ref.set("Hello");
    }
}
r.run();

Additionally it is sometimes useful to keep the reference in other places than in shared memory, e.g. in a ThreadLocal or in case of a web application in a scoped reference or even in combination with some other persistence mechanism. Basically I am proposing the interface ObjectReference:

/**
 * Interface to reference an object.
 * 
 * @param <T> the type of the referenced object
 * @author Apache Software Foundation
 * @since 3.0
 */
public interface ObjectReference<T> {
    /**
     * Getter for the referenced object.
     * 
     * @return the object or <code>null</code>
     */
    T get();

    /**
     * Setter for the reference.
     * 
     * @param object the object to reference (may be <code>null</code>)
     */
    void set(T object);
}

and the two implementations MemoryReference and ThreadLocalReference in the new package org.apache.commons.lang3.reference. I've seen such or similar types in various libraries.

Comments?

Unit test will be provided also.