ProxyTest.java Source code

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Here is the source code for ProxyTest.java

Source

/*
   This program is a part of the companion code for Core Java 8th ed.
   (http://horstmann.com/corejava)
    
   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.
    
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
    
   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

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.
 * @version 1.00 2000-04-13
 * @author Cay Horstmann
 */
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 {
    /**
     * Constructs a TraceHandler
     * @param t the implicit parameter of the method call
     */
    public TraceHandler(Object t) {
        target = t;
    }

    public Object invoke(Object proxy, Method m, Object[] args) throws Throwable {
        // print implicit argument
        System.out.print(target);
        // print method name
        System.out.print("." + m.getName() + "(");
        // print explicit arguments
        if (args != null) {
            for (int i = 0; i < args.length; i++) {
                System.out.print(args[i]);
                if (i < args.length - 1)
                    System.out.print(", ");
            }
        }
        System.out.println(")");

        // invoke actual method
        return m.invoke(target, args);
    }

    private Object target;
}