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ProxyTest.java
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ProxyTest.java
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package proxy;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.Arrays;
import java.util.Random;
/**
* This program demonstrates the use of proxies.
*
* @author Cay Horstmann
* @version 1.00 2000-04-13
*/
public class ProxyTest {
public static void main(String[] args) {
Object[] elements = new Object[1000];
// fill elements with proxies for the integers 1 ... 1000
for (int i = 0; i < elements.length; i++) {
Integer value = i + 1;
InvocationHandler handler = new TraceHandler(value);
Object proxy = Proxy.newProxyInstance(null,
new Class[]{Comparable.class}, handler);
elements[i] = proxy;
}
// construct a random integer
Integer key = new Random().nextInt(elements.length) + 1;
// search for the key
int result = Arrays.binarySearch(elements, key);
// print match if found
if (result >= 0) System.out.println(elements[result]);
}
}
/**
* An invocation handler that prints out the method name and parameters, then
* invokes the original method
*/
class TraceHandler implements InvocationHandler {
private final Object target;
/**
* Construct a TraceHandler
*
* @param t the implicit parameter of the methode call
*/
public TraceHandler(Object t) {
target = t;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
// print implicit argument
System.out.println(target);
// print method name
System.out.println("." + method.getName() + "(");
// print explicit arguments
if (args != null) {
for (int i = 0; i < args.length; i++) {
System.out.println(args[i]);
if (i < args.length - 1) System.out.println(", ");
}
}
System.out.println(")");
// invoke actual method
return method.invoke(target, args);
}
}