corejava第10版

corejava第10版/v1ch06/proxy/ProxyTest.java

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+package proxy;
+
+import java.lang.reflect.*;
+import java.util.*;
+
+/**
+ * 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
+{
+   private Object target;
+
+   /**
+    * 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);
+   }
+}