动态代理
Sun对动态代理的说明：
一个简单例子代码：
动态代理的内部实现——代码生成：
研究JDK源代码，发现在Proxy的sun实现中调用了sun.misc.ProxyGenerator类的generateProxyClass( proxyName, interfaces)方法，其返回值为byte[]和class文件的内存类型一致。于是做如下试验：
public class ProxyClassFile{
public static void main(String[] args){
String proxyName = "TempProxy";
TempImpl t = new TempImpl("proxy");
Class[] interfaces =t.getClass().getInterfaces();
byte[] proxyClassFile = ProxyGenerator.generateProxyClass(
proxyName, interfaces);
File f = new File("classes/TempProxy.class");
try {
FileOutputStream fos = new FileOutputStream(f);
fos.write(proxyClassFile);
fos.flush();
fos.close();
} catch (FileNotFoundException e) {
e.printStackTrace(); //To change body of catch statement use File | Settings | File Templates.
} catch (IOException e) {
e.printStackTrace(); //To change body of catch statement use File | Settings | File Templates.
}
}
}
运行该类，到class文件夹下，利用反编译技术，发现原来其采用了代码生产技术：
public interface Temp{
public void Talk();
public void Run();
}
import java.lang.reflect.*;
public final class TempProxy extends Proxy
implements Temp{
private static Method m4;
private static Method m2;
private static Method m0;
private static Method m3;
private static Method m1;
public TempProxy(InvocationHandler invocationhandler) {
super(invocationhandler);
}
public final void Run() {
try {
h.invoke(this, m4, null);
return;
}
catch(Error _ex) { }
catch(Throwable throwable) {
throw new UndeclaredThrowableException(throwable);
}
}
public final String toString(){
try{
return (String)h.invoke(this, m2, null);
}
catch(Error _ex) { }
catch(Throwable throwable) {
throw new UndeclaredThrowableException(throwable);
}
return "";
}
public final int hashCode() {
try {
return ((Integer)h.invoke(this, m0, null)).intValue();
}
catch(Error _ex) { }
catch(Throwable throwable){
throw new UndeclaredThrowableException(throwable);
}
return 123;
}
public final void Talk(){
try{
h.invoke(this, m3, null);
return;
}
catch(Error _ex) { }
catch(Throwable throwable) {
throw new UndeclaredThrowableException(throwable);
}
}
public final boolean equals(Object obj) {
try {
return ((Boolean)h.invoke(this, m1, new Object[] {
obj
})).booleanValue();
}
catch(Error _ex) { }
catch(Throwable throwable) {
throw new UndeclaredThrowableException(throwable);
}
return false;
}
static{
try{
m4 = Class.forName("Temp").getMethod("Run", new Class[0]);
m2 = Class.forName("java.lang.Object").getMethod("toString", new Class[0]);
m0 = Class.forName("java.lang.Object").getMethod("hashCode", new Class[0]);
m3 = Class.forName("Temp").getMethod("Talk", new Class[0]);
m1 = Class.forName("java.lang.Object").getMethod("equals", new Class[] {
Class.forName("java.lang.Object")
});
}
catch(NoSuchMethodException nosuchmethodexception) {
throw new NoSuchMethodError(nosuchmethodexception.getMessage());
}
catch(ClassNotFoundException classnotfoundexception) {
throw new NoClassDefFoundError(classnotfoundexception.getMessage());
}
}
}
返回JVM技术，反射与动态代理（一）