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| Demonstrates the use of interface based proxies | |
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/*
joeyin
Our Proxy works!
*/
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
/*
*
* This software is granted under the terms of the Common Public License,
* CPL, which may be found at the following URL:
* http://www-124.ibm.com/developerworks/oss/CPLv1.0.htm
*
* Copyright(c) 2003-2005 by the authors indicated in the @author tags.
* All Rights are Reserved by the various authors.
*
########## DO NOT EDIT ABOVE THIS LINE ########## */
/**
* Demonstrates the use of interface based proxies.
*
* @author <a href=mailto:[email protected]>Robert Simmons jr. (kraythe)</a>
* @version $Revision: 1.2 $
*/
public class DemoInterfaceProxy {
/**
* Use a proxy and check the count.
*/
public static final void checkCount() {
SomeClass proxy = SomeClassFactory.getSomeClassProxy();
proxy.someMethod();
proxy.someOtherMethod("Our Proxy works!");
if (proxy instanceof SomeClassCountingProxy) {
System.out.println(((SomeClassCountingProxy)proxy).getInvocationCount());
}
}
/**
* Run the demonstration.
*
* @param args Command Line Arguments (ignored).
*/
public static final void main(final String[] args) {
SomeClass proxy = SomeClassFactory.getSomeClassProxy();
proxy.someMethod();
proxy.someOtherMethod("Our Proxy works!");
}
}
class SomeClassFactory {
/**
* Gets a counting proxy to an object that is constructed with the user name.
*
* @return The proxy to the implementation.
*/
public static final SomeClassCountingProxy getCountingProxy() {
SomeClassImpl impl = new SomeClassImpl(System.getProperty("user.name"));
return new SomeClassCountingProxy(impl);
}
/**
* Gets proxy to depending upon debug status in Log4J.
*
* @return The proxy to the implementation.
*/
public static final SomeClass getDynamicSomeClassProxy() {
SomeClassImpl impl = new SomeClassImpl(System.getProperty("user.name"));
InvocationHandler handler = new MethodCountingHandler(impl);
Class[] interfaces = new Class[] { SomeClass.class };
ClassLoader loader = SomeClassFactory.class.getClassLoader();
SomeClass proxy = (SomeClass) Proxy.newProxyInstance(loader, interfaces, handler);
return proxy;
}
/**
* Gets a proxy to an object that is constructed with the user name.
*
* @return The proxy to the implementation.
*/
public static final SomeClassProxy getProxy() {
SomeClassImpl impl = new SomeClassImpl(System.getProperty("user.name"));
return new SomeClassProxy(impl);
}
/**
* Gets proxy to depending upon debug status in Log4J.
*
* @return The proxy to the implementation.
*/
public static final SomeClass getSomeClassProxy() {
SomeClassImpl impl = new SomeClassImpl(System.getProperty("user.name"));
if (true) {
return new SomeClassCountingProxy(impl);
} else {
return new SomeClassProxy(impl);
}
}
}
class SomeClassCountingProxy implements SomeClass {
/** The implementation object for this proxy. */
private final SomeClassImpl impl;
/** Holds the invocation count. */
private int invocationCount = 0;
/**
* Creates a new SomeClassProxy object.
*
* @param impl The implementation object for this proxy.
*/
public SomeClassCountingProxy(final SomeClassImpl impl) {
this.impl = impl;
}
/**
* Gets the value of the property invocationCount.
*
* @return The current value of invocationCount
*/
public int getInvocationCount() {
return invocationCount;
}
/**
* @see java2s.hcj.proxies.SomeClass#someMethod()
*/
public void someMethod() {
this.invocationCount++;
this.impl.someMethod();
}
/**
* @see java2s.hcj.proxies.SomeClass#someOtherMethod(java.lang.String)
*/
public void someOtherMethod(String text) {
this.invocationCount++;
this.impl.someOtherMethod(text);
}
}
class SomeClassImpl implements SomeClass {
/** Holds the user name. */
private String userName;
/**
* Creates a new SomeClass object.
*
* @param userName
* The user name to use.
*/
public SomeClassImpl(final String userName) {
this.userName = userName;
}
/**
* @see java2s.hcj.proxies.SomeClass#someOtherMethod(java.lang.String)
*/
public void someMethod() {
System.out.println(this.userName);
}
/**
* @see java2s.hcj.proxies.SomeClass#someOtherMethod(java.lang.String)
*/
public void someOtherMethod(final String text) {
System.out.println(text);
}
}
class SomeClassProxy implements SomeClass {
/** The impl object for this proxy. */
private final SomeClassImpl impl;
/**
* Creates a new SomeClassProxy object.
*
* @param impl
* The implementation object for this proxy.
*/
public SomeClassProxy(final SomeClassImpl impl) {
this.impl = impl;
}
/**
* @see java2s.hcj.proxies.SomeClass#someMethod()
*/
public void someMethod() {
this.impl.someMethod();
}
/**
* @see java2s.hcj.proxies.SomeClass#someOtherMethod(java.lang.String)
*/
public void someOtherMethod(String text) {
this.impl.someOtherMethod(text);
}
}
interface SomeClass {
/**
* Print out the user name.
*/
public abstract void someMethod();
/**
* Print out the string given to us.
*
* @param text
* The string to print.
*/
public abstract void someOtherMethod(final String text);
}
/**
* An invocation handler that counts the number of calls for all methods in the
* target class.
*
* @author <a href=mailto:[email protected]>Robert Simmons jr. (kraythe)</a>
* @version $Revision: 1.2 $
*
* @see java.lang.reflect.InvocationHandler
*/
class MethodCountingHandler implements InvocationHandler {
/** The implementation object for this proxy. */
private final Object impl;
/** Holds the invocation count. */
private int invocationCount = 0;
/**
* Creates a new MethodCOuntingHandler object.
*
* @param impl
*/
public MethodCountingHandler(final Object impl) {
this.impl = impl;
}
/**
* Gets the value of the property invocationCount.
*
* @return The current value of invocationCount
*/
public int getInvocationCount() {
return invocationCount;
}
/**
* @see java.lang.reflect.InvocationHandler#invoke(java.lang.Object,
* java.lang.reflect.Method, java.lang.Object[])
*/
public Object invoke(Object proxy, Method meth, Object[] args) throws Throwable {
try {
this.invocationCount++;
Object result = meth.invoke(impl, args);
return result;
} catch (final InvocationTargetException ex) {
throw ex.getTargetException();
}
}
}
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