從另一個角度理解Java中的動態(tài)代理機(jī)制

package samples; 
/** 
 * 程序猿類 
 * @author louluan 
 */ 
public class Programmer { 
 
 public void code() 
 { 
  System.out.println("I'm a Programmer,Just Coding....."); 
 } 
} 

package samples; 
/** 
 * 自定義一個類加載器，用于將字節(jié)碼轉(zhuǎn)換為class對象 
 * @author louluan 
 */ 
public class MyClassLoader extends ClassLoader { 
 
 public Class<&#63;> defineMyClass( byte[] b, int off, int len) 
 { 
  return super.defineClass(b, off, len); 
 } 
  
} 

package samples; 
 
import java.io.File; 
import java.io.FileInputStream; 
import java.io.FileNotFoundException; 
import java.io.IOException; 
import java.io.InputStream; 
import java.net.URL; 
 
public class MyTest { 
 
 public static void main(String[] args) throws IOException { 
  //讀取本地的class文件內(nèi)的字節(jié)碼，轉(zhuǎn)換成字節(jié)碼數(shù)組 
  File file = new File("."); 
  InputStream input = new FileInputStream(file.getCanonicalPath()+"\\bin\\samples\\Programmer.class"); 
  byte[] result = new byte[1024]; 
   
  int count = input.read(result); 
  // 使用自定義的類加載器將 byte字節(jié)碼數(shù)組轉(zhuǎn)換為對應(yīng)的class對象 
  MyClassLoader loader = new MyClassLoader(); 
  Class clazz = loader.defineMyClass( result, 0, count); 
  //測試加載是否成功，打印class 對象的名稱 
  System.out.println(clazz.getCanonicalName()); 
     
    //實(shí)例化一個Programmer對象 
    Object o= clazz.newInstance(); 
    try { 
     //調(diào)用Programmer的code方法 
     clazz.getMethod("code", null).invoke(o, null); 
     } catch (IllegalArgumentException | InvocationTargetException 
      | NoSuchMethodException | SecurityException e) { 
      e.printStackTrace(); 
     } 
 } 
} 

package com.samples; 
import java.io.PrintStream; 
 
public class Programmer { 
 
 public void code() 
 { 
  System.out.println("I'm a Programmer,Just Coding....."); 
 } 
} 

package samples; 
 
import java.io.File; 
import java.io.FileOutputStream; 
import java.io.IOException; 
 
import org.objectweb.asm.ClassWriter; 
import org.objectweb.asm.MethodVisitor; 
import org.objectweb.asm.Opcodes; 
public class MyGenerator { 
 
 public static void main(String[] args) throws IOException { 
 
  System.out.println(); 
  ClassWriter classWriter = new ClassWriter(0); 
  // 通過visit方法確定類的頭部信息 
  classWriter.visit(Opcodes.V1_7,// java版本 
    Opcodes.ACC_PUBLIC,// 類修飾符 
    "Programmer", // 類的全限定名 
    null, "java/lang/Object", null); 
   
  //創(chuàng)建構(gòu)造函數(shù) 
  MethodVisitor mv = classWriter.visitMethod(Opcodes.ACC_PUBLIC, "<init>", "()V", null, null); 
  mv.visitCode(); 
  mv.visitVarInsn(Opcodes.ALOAD, 0); 
  mv.visitMethodInsn(Opcodes.INVOKESPECIAL, "java/lang/Object", "<init>","()V"); 
  mv.visitInsn(Opcodes.RETURN); 
  mv.visitMaxs(1, 1); 
  mv.visitEnd(); 
   
  // 定義code方法 
  MethodVisitor methodVisitor = classWriter.visitMethod(Opcodes.ACC_PUBLIC, "code", "()V", 
    null, null); 
  methodVisitor.visitCode(); 
  methodVisitor.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/System", "out", 
    "Ljava/io/PrintStream;"); 
  methodVisitor.visitLdcInsn("I'm a Programmer,Just Coding....."); 
  methodVisitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/io/PrintStream", "println", 
    "(Ljava/lang/String;)V"); 
  methodVisitor.visitInsn(Opcodes.RETURN); 
  methodVisitor.visitMaxs(2, 2); 
  methodVisitor.visitEnd(); 
  classWriter.visitEnd(); 
  // 使classWriter類已經(jīng)完成 
  // 將classWriter轉(zhuǎn)換成字節(jié)數(shù)組寫到文件里面去 
  byte[] data = classWriter.toByteArray(); 
  File file = new File("D://Programmer.class"); 
  FileOutputStream fout = new FileOutputStream(file); 
  fout.write(data); 
  fout.close(); 
 } 
} 

import javassist.ClassPool; 
import javassist.CtClass; 
import javassist.CtMethod; 
import javassist.CtNewMethod; 
 
public class MyGenerator { 
 
 public static void main(String[] args) throws Exception { 
  ClassPool pool = ClassPool.getDefault(); 
  //創(chuàng)建Programmer類  
  CtClass cc= pool.makeClass("com.samples.Programmer"); 
  //定義code方法 
  CtMethod method = CtNewMethod.make("public void code(){}", cc); 
  //插入方法代碼 
  method.insertBefore("System.out.println(\"I'm a Programmer,Just Coding.....\");"); 
  cc.addMethod(method); 
  //保存生成的字節(jié)碼 
  cc.writeFile("d://temp"); 
 } 
} 

package com.foo.proxy; 
 
/** 
 * 售票服務(wù)接口實(shí)現(xiàn)類，車站 
 * @author louluan 
 */ 
public class Station implements TicketService { 
 
 @Override 
 public void sellTicket() { 
  System.out.println("\n\t售票.....\n"); 
 } 
 
 @Override 
 public void inquire() { 
  System.out.println("\n\t問詢。。。。\n"); 
 } 
 
 @Override 
 public void withdraw() { 
  System.out.println("\n\t退票......\n"); 
 } 
 
} 

package com.foo.proxy; 
/** 
 * 售票服務(wù)接口 
 * @author louluan 
 */ 
public interface TicketService { 
 
 //售票 
 public void sellTicket(); 
  
 //問詢 
 public void inquire(); 
  
 //退票 
 public void withdraw(); 
  
} 

package com.foo.proxy; 
 
/** 
 * 車票代售點(diǎn) 
 * @author louluan 
 * 
 */ 
public class StationProxy implements TicketService { 
 
 private Station station; 
 
 public StationProxy(Station station){ 
  this.station = station; 
 } 
  
 @Override 
 public void sellTicket() { 
 
  // 1.做真正業(yè)務(wù)前，提示信息 
  this.showAlertInfo("××××您正在使用車票代售點(diǎn)進(jìn)行購票，每張票將會收取5元手續(xù)費(fèi)！××××"); 
  // 2.調(diào)用真實(shí)業(yè)務(wù)邏輯 
  station.sellTicket(); 
  // 3.后處理 
  this.takeHandlingFee(); 
  this.showAlertInfo("××××歡迎您的光臨，再見！××××\n"); 
 
 } 
 
 @Override 
 public void inquire() { 
  // 1做真正業(yè)務(wù)前，提示信息 
  this.showAlertInfo("××××歡迎光臨本代售點(diǎn)，問詢服務(wù)不會收取任何費(fèi)用，本問詢信息僅供參考，具體信息以車站真實(shí)數(shù)據(jù)為準(zhǔn)！××××"); 
  // 2.調(diào)用真實(shí)邏輯 
  station.inquire(); 
  // 3。后處理 
  this.showAlertInfo("××××歡迎您的光臨，再見！××××\n"); 
 } 
 
 @Override 
 public void withdraw() { 
  // 1。真正業(yè)務(wù)前處理 
  this.showAlertInfo("××××歡迎光臨本代售點(diǎn)，退票除了扣除票額的20%外，本代理處額外加收2元手續(xù)費(fèi)！××××"); 
  // 2.調(diào)用真正業(yè)務(wù)邏輯 
  station.withdraw(); 
  // 3.后處理 
  this.takeHandlingFee(); 
 
 } 
 
 /* 
  * 展示額外信息 
  */ 
 private void showAlertInfo(String info) { 
  System.out.println(info); 
 } 
 
 /* 
  * 收取手續(xù)費(fèi) 
  */ 
 private void takeHandlingFee() { 
  System.out.println("收取手續(xù)費(fèi)，打印發(fā)票。。。。。\n"); 
 } 
 
} 

package com.foo.proxy; 
 
import java.lang.reflect.Constructor; 
 
import javassist.*; 
public class Test { 
 
 public static void main(String[] args) throws Exception { 
  createProxy(); 
 } 
  
 /* 
  * 手動創(chuàng)建字節(jié)碼 
  */ 
 private static void createProxy() throws Exception 
 { 
  ClassPool pool = ClassPool.getDefault(); 
 
  CtClass cc = pool.makeClass("com.foo.proxy.StationProxy"); 
   
  //設(shè)置接口 
  CtClass interface1 = pool.get("com.foo.proxy.TicketService"); 
  cc.setInterfaces(new CtClass[]{interface1}); 
   
  //設(shè)置Field 
  CtField field = CtField.make("private com.foo.proxy.Station station;", cc); 
   
  cc.addField(field); 
   
  CtClass stationClass = pool.get("com.foo.proxy.Station"); 
  CtClass[] arrays = new CtClass[]{stationClass}; 
  CtConstructor ctc = CtNewConstructor.make(arrays,null,CtNewConstructor.PASS_NONE,null,null, cc); 
  //設(shè)置構(gòu)造函數(shù)內(nèi)部信息 
  ctc.setBody("{this.station=$1;}"); 
  cc.addConstructor(ctc); 
 
  //創(chuàng)建收取手續(xù) takeHandlingFee方法 
  CtMethod takeHandlingFee = CtMethod.make("private void takeHandlingFee() {}", cc); 
  takeHandlingFee.setBody("System.out.println(\"收取手續(xù)費(fèi)，打印發(fā)票。。。。。\");"); 
  cc.addMethod(takeHandlingFee); 
   
  //創(chuàng)建showAlertInfo 方法 
  CtMethod showInfo = CtMethod.make("private void showAlertInfo(String info) {}", cc); 
  showInfo.setBody("System.out.println($1);"); 
  cc.addMethod(showInfo); 
   
  //sellTicket 
  CtMethod sellTicket = CtMethod.make("public void sellTicket(){}", cc); 
  sellTicket.setBody("{this.showAlertInfo(\"××××您正在使用車票代售點(diǎn)進(jìn)行購票，每張票將會收取5元手續(xù)費(fèi)！××××\");" 
    + "station.sellTicket();" 
    + "this.takeHandlingFee();" 
    + "this.showAlertInfo(\"××××歡迎您的光臨，再見！××××\");}"); 
  cc.addMethod(sellTicket); 
   
  //添加inquire方法 
  CtMethod inquire = CtMethod.make("public void inquire() {}", cc); 
  inquire.setBody("{this.showAlertInfo(\"××××歡迎光臨本代售點(diǎn)，問詢服務(wù)不會收取任何費(fèi)用，本問詢信息僅供參考，具體信息以車站真實(shí)數(shù)據(jù)為準(zhǔn)！××××\");" 
  + "station.inquire();" 
  + "this.showAlertInfo(\"××××歡迎您的光臨，再見！××××\");}" 
  ); 
  cc.addMethod(inquire); 
   
  //添加widthraw方法 
  CtMethod withdraw = CtMethod.make("public void withdraw() {}", cc); 
  withdraw.setBody("{this.showAlertInfo(\"××××歡迎光臨本代售點(diǎn)，退票除了扣除票額的20%外，本代理處額外加收2元手續(xù)費(fèi)！××××\");" 
    + "station.withdraw();" 
    + "this.takeHandlingFee();}" 
    ); 
  cc.addMethod(withdraw); 
   
  //獲取動態(tài)生成的class 
  Class c = cc.toClass(); 
  //獲取構(gòu)造器 
  Constructor constructor= c.getConstructor(Station.class); 
  //通過構(gòu)造器實(shí)例化 
  TicketService o = (TicketService)constructor.newInstance(new Station()); 
  o.inquire(); 
   
  cc.writeFile("D://test"); 
 } 
  
} 

package com.foo.proxy; 
 
import java.lang.reflect.InvocationHandler; 
import java.lang.reflect.Proxy; 
 
public class Test { 
 
 public static void main(String[] args) { 
 
  ElectricCar car = new ElectricCar(); 
  // 1.獲取對應(yīng)的ClassLoader 
  ClassLoader classLoader = car.getClass().getClassLoader(); 
 
  // 2.獲取ElectricCar 所實(shí)現(xiàn)的所有接口 
  Class[] interfaces = car.getClass().getInterfaces(); 
  // 3.設(shè)置一個來自代理傳過來的方法調(diào)用請求處理器，處理所有的代理對象上的方法調(diào)用 
  InvocationHandler handler = new InvocationHandlerImpl(car); 
  /* 
   4.根據(jù)上面提供的信息，創(chuàng)建代理對象 在這個過程中， 
       a.JDK會通過根據(jù)傳入的參數(shù)信息動態(tài)地在內(nèi)存中創(chuàng)建和.class 文件等同的字節(jié)碼 
     b.然后根據(jù)相應(yīng)的字節(jié)碼轉(zhuǎn)換成對應(yīng)的class， 
       c.然后調(diào)用newInstance()創(chuàng)建實(shí)例 
   */ 
  Object o = Proxy.newProxyInstance(classLoader, interfaces, handler); 
  Vehicle vehicle = (Vehicle) o; 
  vehicle.drive(); 
  Rechargable rechargeable = (Rechargable) o; 
  rechargeable.recharge(); 
 } 
} 

package com.foo.proxy; 
/** 
 * 交通工具接口 
 * @author louluan 
 */ 
public interface Vehicle { 
 public void drive(); 
} 

package com.foo.proxy; 
/** 
 * 可充電設(shè)備接口 
 * @author louluan 
 */ 
public interface Rechargable { 
 
 public void recharge(); 
} 

package com.foo.proxy; 
/** 
 * 電能車類，實(shí)現(xiàn)Rechargable，Vehicle接口 
 * @author louluan 
 */ 
public class ElectricCar implements Rechargable, Vehicle { 
 
 @Override 
 public void drive() { 
  System.out.println("Electric Car is Moving silently..."); 
 } 
 
 @Override 
 public void recharge() { 
  System.out.println("Electric Car is Recharging..."); 
 } 
 
} 

package com.foo.proxy; 
 
import java.lang.reflect.InvocationHandler; 
import java.lang.reflect.Method; 
 
public class InvocationHandlerImpl implements InvocationHandler { 
 
 private ElectricCar car; 
  
 public InvocationHandlerImpl(ElectricCar car) 
 { 
  this.car=car; 
 } 
  
 @Override 
 public Object invoke(Object paramObject, Method paramMethod, 
   Object[] paramArrayOfObject) throws Throwable { 
  System.out.println("You are going to invoke "+paramMethod.getName()+" ..."); 
  paramMethod.invoke(car, null); 
  System.out.println(paramMethod.getName()+" invocation Has Been finished..."); 
  return null; 
 } 
 
} 

package com.foo.proxy; 
 
import java.io.FileOutputStream; 
import java.io.IOException; 
import java.lang.reflect.Proxy; 
import sun.misc.ProxyGenerator; 
 
public class ProxyUtils { 
 
 /* 
  * 將根據(jù)類信息 動態(tài)生成的二進(jìn)制字節(jié)碼保存到硬盤中， 
  * 默認(rèn)的是clazz目錄下 
   * params :clazz 需要生成動態(tài)代理類的類 
   * proxyName : 為動態(tài)生成的代理類的名稱 
   */ 
 public static void generateClassFile(Class clazz,String proxyName) 
 { 
  //根據(jù)類信息和提供的代理類名稱，生成字節(jié)碼 
    byte[] classFile = ProxyGenerator.generateProxyClass(proxyName, clazz.getInterfaces()); 
  String paths = clazz.getResource(".").getPath(); 
  System.out.println(paths); 
  FileOutputStream out = null; 
   
  try { 
   //保留到硬盤中 
   out = new FileOutputStream(paths+proxyName+".class"); 
   out.write(classFile); 
   out.flush(); 
  } catch (Exception e) { 
   e.printStackTrace(); 
  } finally { 
   try { 
    out.close(); 
   } catch (IOException e) { 
    e.printStackTrace(); 
   } 
  } 
 } 
  
} 

import com.foo.proxy.Rechargable; 
import com.foo.proxy.Vehicle; 
import java.lang.reflect.InvocationHandler; 
import java.lang.reflect.Method; 
import java.lang.reflect.Proxy; 
import java.lang.reflect.UndeclaredThrowableException; 
/** 
 生成的動態(tài)代理類的組織模式是繼承Proxy類，然后實(shí)現(xiàn)需要實(shí)現(xiàn)代理的類上的所有接口，而在實(shí)現(xiàn)的過程中，則是通過將所有的方法都交給了InvocationHandler來處理 
*/ 
 public final class ElectricCarProxy extends Proxy 
 implements Rechargable, Vehicle 
{ 
 private static Method m1; 
 private static Method m3; 
 private static Method m4; 
 private static Method m0; 
 private static Method m2; 
 
 public ElectricCarProxy(InvocationHandler paramInvocationHandler) 
 throws 
 { 
 super(paramInvocationHandler); 
 } 
 
 public final boolean equals(Object paramObject) 
 throws 
 { 
 try 
 { // 方法功能實(shí)現(xiàn)交給InvocationHandler處理 
  return ((Boolean)this.h.invoke(this, m1, new Object[] { paramObject })).booleanValue(); 
 } 
 catch (Error|RuntimeException localError) 
 { 
  throw localError; 
 } 
 catch (Throwable localThrowable) 
 { 
  throw new UndeclaredThrowableException(localThrowable); 
 } 
 } 
 
 public final void recharge() 
 throws 
 { 
 try 
 { 
 
  // 方法功能實(shí)現(xiàn)交給InvocationHandler處理 
 
  this.h.invoke(this, m3, null); 
  return; 
 } 
 catch (Error|RuntimeException localError) 
 { 
  throw localError; 
 } 
 catch (Throwable localThrowable) 
 { 
  throw new UndeclaredThrowableException(localThrowable); 
 } 
 } 
 
 public final void drive() 
 throws 
 { 
 try 
 { 
 
  // 方法功能實(shí)現(xiàn)交給InvocationHandler處理 
 
  this.h.invoke(this, m4, null); 
  return; 
 } 
 catch (Error|RuntimeException localError) 
 { 
  throw localError; 
 } 
 catch (Throwable localThrowable) 
 { 
  throw new UndeclaredThrowableException(localThrowable); 
 } 
 } 
 
 public final int hashCode() 
 throws 
 { 
 try 
 { 
 
  // 方法功能實(shí)現(xiàn)交給InvocationHandler處理 
 
  return ((Integer)this.h.invoke(this, m0, null)).intValue(); 
 } 
 catch (Error|RuntimeException localError) 
 { 
  throw localError; 
 } 
 catch (Throwable localThrowable) 
 { 
  throw new UndeclaredThrowableException(localThrowable); 
 } 
 } 
 
 public final String toString() 
 throws 
 { 
 try 
 { 
 
  // 方法功能實(shí)現(xiàn)交給InvocationHandler處理 
  return (String)this.h.invoke(this, m2, null); 
 } 
 catch (Error|RuntimeException localError) 
 { 
  throw localError; 
 } 
 catch (Throwable localThrowable) 
 { 
  throw new UndeclaredThrowableException(localThrowable); 
 } 
 } 
 
 static 
 { 
 try 
 { //為每一個需要方法對象，當(dāng)調(diào)用相應(yīng)的方法時(shí)，分別將方法對象作為參數(shù)傳遞給InvocationHandler處理 
  m1 = Class.forName("java.lang.Object").getMethod("equals", new Class[] { Class.forName("java.lang.Object") }); 
  m3 = Class.forName("com.foo.proxy.Rechargable").getMethod("recharge", new Class[0]); 
  m4 = Class.forName("com.foo.proxy.Vehicle").getMethod("drive", new Class[0]); 
  m0 = Class.forName("java.lang.Object").getMethod("hashCode", new Class[0]); 
  m2 = Class.forName("java.lang.Object").getMethod("toString", new Class[0]); 
  return; 
 } 
 catch (NoSuchMethodException localNoSuchMethodException) 
 { 
  throw new NoSuchMethodError(localNoSuchMethodException.getMessage()); 
 } 
 catch (ClassNotFoundException localClassNotFoundException) 
 { 
  throw new NoClassDefFoundError(localClassNotFoundException.getMessage()); 
 } 
 } 
} 

package samples; 
/** 
 * 程序猿類 
 * @author louluan 
 */ 
public class Programmer { 
 
 public void code() 
 { 
  System.out.println("I'm a Programmer,Just Coding....."); 
 } 
} 

package samples; 
 
import java.lang.reflect.Method; 
 
import net.sf.cglib.proxy.MethodInterceptor; 
import net.sf.cglib.proxy.MethodProxy; 
/* 
 * 實(shí)現(xiàn)了方法攔截器接口 
 */ 
public class Hacker implements MethodInterceptor { 
 @Override 
 public Object intercept(Object obj, Method method, Object[] args, 
   MethodProxy proxy) throws Throwable { 
  System.out.println("**** I am a hacker,Let's see what the poor programmer is doing Now..."); 
  proxy.invokeSuper(obj, args); 
  System.out.println("**** Oh,what a poor programmer....."); 
  return null; 
 } 
 
} 

package samples; 
 
import net.sf.cglib.proxy.Enhancer; 
 
public class Test { 
 
 public static void main(String[] args) { 
  Programmer progammer = new Programmer(); 
   
  Hacker hacker = new Hacker(); 
  //cglib 中加強(qiáng)器，用來創(chuàng)建動態(tài)代理 
  Enhancer enhancer = new Enhancer(); 
     //設(shè)置要創(chuàng)建動態(tài)代理的類 
  enhancer.setSuperclass(progammer.getClass()); 
    // 設(shè)置回調(diào)，這里相當(dāng)于是對于代理類上所有方法的調(diào)用，都會調(diào)用CallBack，而Callback則需要實(shí)行intercept()方法進(jìn)行攔截 
    enhancer.setCallback(hacker); 
    Programmer proxy =(Programmer)enhancer.create(); 
    proxy.code(); 
   
 } 
} 

package samples; 
 
import java.lang.reflect.Method; 
import net.sf.cglib.core.ReflectUtils; 
import net.sf.cglib.core.Signature; 
import net.sf.cglib.proxy.Callback; 
import net.sf.cglib.proxy.Factory; 
import net.sf.cglib.proxy.MethodInterceptor; 
import net.sf.cglib.proxy.MethodProxy; 
 
public class Programmer
EnhancerByCGLIB
fa7aa2cd extends Programmer 
 implements Factory 
{ 
 //......省略 
 private MethodInterceptor CGLIB$CALLBACK_0; // Enchaner傳入的methodInterceptor 
 // ....省略 
 public final void code() 
 { 
 MethodInterceptor tmp4_1 = this.CGLIB$CALLBACK_0; 
 if (tmp4_1 == null) 
 { 
  tmp4_1; 
  CGLIB$BIND_CALLBACKS(this);//若callback 不為空，則調(diào)用methodInterceptor 的intercept()方法 
 } 
 if (this.CGLIB$CALLBACK_0 != null) 
  return; 
  //如果沒有設(shè)置callback回調(diào)函數(shù)，則默認(rèn)執(zhí)行父類的方法 
  super.code(); 
 } 
 //....后續(xù)省略 
}