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POAccessing fields from a proxied object
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copied!<p>I've run into an interesting problem while developing an ORM framework for Android. I'm using a library called <a href="http://code.google.com/p/dexmaker/" rel="noreferrer">dexmaker</a> for bytecode manipulation, which enables me to create proxies for persistent objects in order to implement lazy loading.</p> <p>The proxied instance has an associated <code>InvocationHandler</code> such that when a method is called on the proxy, the <code>invoke</code> method is called on the <code>InvocationHandler</code>, which then calls the proxied object's respective method assuming it's been lazily loaded. Nothing too surprising -- it's just like Java's <a href="http://docs.oracle.com/javase/1.4.2/docs/api/java/lang/reflect/Proxy.html" rel="noreferrer">Proxy</a> class but allows me to proxy actual classes instead of interfaces (see dexmaker's <a href="http://dexmaker.googlecode.com/git/javadoc/com/google/dexmaker/stock/ProxyBuilder.html" rel="noreferrer">ProxyBuilder</a>).</p> <p>The part that's become problematic is that I also use reflection to retrieve field values from persistent objects and -- now that I've introduced lazy loading -- proxies. Here is what I'm currently doing:</p> <pre><code>for (Field f : getPersistentFields(model.getClass()) { ... Object val = f.get(model); // model is either a persistent object or a proxy for one mapField(f, val, map); } </code></pre> <p>This of course works for regular model instances, but for proxied instances, <code>f.get(model)</code> is not retrieving the proxied object's field value. Instead, it's returning the default value assigned in the class's constructor. The access on the proxy's field is not being intercepted obviously.</p> <p><strong>My question is this:</strong> is there any way I can intercept an access on a proxy's member variable made through reflection? If not, how can I retrieve the value of a proxy's field in a "reflection-like" way?</p> <p><strong>One possible workaround</strong> I'm thinking of would be to retrieve and then invoke the field's getter method using reflection, but I'm wondering if there's a more direct solution. This workaround, if it actually <em>works</em>, would require the object to have a getter method for all persistent fields -- a requirement that should typically be followed from an OO-design point of view but also forces more work onto the user of the framework.</p> <p>I'm open to any ideas.</p>

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