66 lines
2.0 KiB
Java
66 lines
2.0 KiB
Java
// generics/DynamicProxyMixin.java
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// (c)2016 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://mindviewinc.com/Books/OnJava/ for more book information.
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import java.lang.reflect.*;
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import java.util.*;
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import onjava.*;
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import static onjava.Tuple.*;
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class MixinProxy implements InvocationHandler {
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Map<String, Object> delegatesByMethod;
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@SuppressWarnings("unchecked")
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public MixinProxy(Tuple2<Object, Class<?>>... pairs) {
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delegatesByMethod = new HashMap<>();
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for(Tuple2<Object, Class<?>> pair : pairs) {
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for(Method method : pair._2.getMethods()) {
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String methodName = method.getName();
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// The first interface in the map
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// implements the method.
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if(!delegatesByMethod.containsKey(methodName))
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delegatesByMethod.put(methodName, pair._1);
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}
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}
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}
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@Override
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public Object invoke(Object proxy, Method method,
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Object[] args) throws Throwable {
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String methodName = method.getName();
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Object delegate = delegatesByMethod.get(methodName);
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return method.invoke(delegate, args);
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}
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@SuppressWarnings("unchecked")
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public static Object newInstance(Tuple2... pairs) {
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Class[] interfaces = new Class[pairs.length];
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for(int i = 0; i < pairs.length; i++) {
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interfaces[i] = (Class)pairs[i]._2;
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}
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ClassLoader cl =
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pairs[0]._1.getClass().getClassLoader();
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return Proxy.newProxyInstance(
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cl, interfaces, new MixinProxy(pairs));
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}
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}
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public class DynamicProxyMixin {
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public static void main(String[] args) {
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Object mixin = MixinProxy.newInstance(
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tuple(new BasicImp(), Basic.class),
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tuple(new TimeStampedImp(), TimeStamped.class),
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tuple(new SerialNumberedImp(),
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SerialNumbered.class));
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Basic b = (Basic)mixin;
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TimeStamped t = (TimeStamped)mixin;
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SerialNumbered s = (SerialNumbered)mixin;
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b.set("Hello");
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System.out.println(b.get());
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System.out.println(t.getStamp());
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System.out.println(s.getSerialNumber());
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}
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}
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/* Output:
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Hello
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1469638238271
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1
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*/
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