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    <p>Serialization is basically deep cloning. </p> <p>You need to track each object reference for reoccurrencies (for example by using <a href="http://java.sun.com/j2se/1.5.0/docs/api/java/util/IdentityHashMap.html" rel="noreferrer">IdentityHashMap</a>). What ever is your final implementation method (if not external library) remember to check for object reoccurrencies or you may end up in an infinent loop (when object A has reference to object B that again has reference to object A or something more complex loop in an object graph). </p> <p>One way is to traverse through object graph with DFS-like algorithm and build the clone (serialized string) from there. </p> <p>This pseudo-code hopefully explains how:</p> <pre><code>visited = {} function visit(node) { if node in visited { doStuffOnReoccurence(node) return } visited.add(node) doStuffBeforeOthers(node) for each otherNode in node.expand() visit(otherNode) doStuffAfterOthers(node) } </code></pre> <p>The visited set in the example is where I would use identity set (if there was one) or IdentityHashMap.</p> <p>When finding out fields reflectively (thats the node.expand() part) remember to go through superclass fields also.</p> <p>Reflection should not be used in a "normal" development case. Reflection handles code as a data and you can ignore all normal object access restrictions. I've used this reflective deep copy stuff only for tests:</p> <ol> <li><p>In a test that checked different kinds of objects for deep object graph equality</p></li> <li><p>In a test that analyzed object graph size and other properties</p></li> </ol>
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    1. POHow to recursively serialize an object using reflection?
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    1. COYeah,you mentioned about IdentityHashMap, I notice that the author of <java reflection in action> also used IdentityHashMap in his example codes.But I don't understand IdentityHashMap, even I've read java documentation about it.
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    2. CODifference compared to normal map is that it uses identity (==) as key instead of equals. When you are making a deep clone you need to know when something is really the same object..
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