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Adding interface to an existing class
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created by <a href="http://community.jboss.org/people/mnrz">mnrz</a> in <i>Javassist</i> - <a href="http://community.jboss.org/message/608679#608679">View the full discussion</a>
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<div class="jive-rendered-content"><p>Hi </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>I have a class which is in legacy system and we cannot change the class. I need to create a java proxy for that class but this is a class without interface. So I have created an interface and write the following code to add this interface to that class at runtime but the class.getInterfaces() method still returns no interface!</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>--</p><p>public class Main {</p><p>    </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>    </p><p>    public static void main(String[] args) throws Exception {</p><p>        //@SuppressWarnings("rawtypes")</p><p>        createInterface();</p><p>        AnAbstractClass instance = new AClassFromAbstract();//instance.getClass().getInterfaces()</p><p>        Object proxy = Proxy.newProxyInstance(ProxyIntAnAbstractClass.class.getClassLoader(), </p><p>                new Class[] {ProxyIntAnAbstractClass.class},</p><p>                new MyInvocationHandler(instance));</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>        ProxyIntAnAbstractClass instance2 = (ProxyIntAnAbstractClass) proxy;</p><p>        instance2.doSomething();</p><p>        instance2.doSomethingElse();</p><p>    }</p><p>    </p><p>    public static Class createInterface() throws Exception{</p><p>        ClassPool pool = ClassPool.getDefault();</p><p>        ClassPath cp = new ClassClassPath(AnAbstractClass.class);</p><p>        pool.insertClassPath(cp);</p><p>        pool.importPackage("com.macquarie.test.proxy");</p><p>        </p><p>        CtClass myinterface = pool.get("com.mmm.test.proxy.ProxyIntAnAbstractClass");</p><p>        </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>        CtClass tclass = pool.getCtClass("com.mmm.test.proxy.AnAbstractClass");</p><p>        tclass.setInterfaces(new CtClass[] {myinterface});</p><p>        tclass.rebuildClassFile();</p><p>        tclass.detach();</p><p>        return myinterface.toClass();</p><p>    </p><p>    </p><p>    }</p><p>}</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>--</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>When I execute this code, since the ProxyIntAnAbstractClass is not interface of AnAbstractClass, InvocationHandler complains that the object is not an instance of declaring class</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>Can you please help me on this?</p></div>
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