[编织消息框架][JAVA核心技术]jdk动态代理

2023-02-23 19:12:49

需要用到的工具 jdk : javac javap

class 反编译：JD-GUI http://jd.benow.ca/

先来看下jdk动态代理跟native性能比较

 package com.eyu.onequeue;

 import java.lang.reflect.InvocationHandler;

 import java.lang.reflect.Method;

 import java.lang.reflect.Proxy;

 public class TestProxy {

     public interface UserService {

     public String getName(int id);

     public Integer getAge(int id);

     }

     public static class UserServiceImpl implements UserService {

     @Override

     public String getName(int id) {

         return "name : " + id;

     }

     @Override

     public Integer getAge(int id) {

         return id;

     }

     };

     public static void main(String[] args) {

     testNative();

     testJdk();

     }

     public static void testJdk() {

     UserService impTarget = new UserServiceImpl();

     // 代理处理逻辑

     InvocationHandler handler = new InvocationHandler() {

         @Override

         public Object invoke(Object target, Method method, Object[] args) throws Throwable {

         return method.invoke(impTarget, args);

         }

     };

     // Proxy.newProxyInstance(ClassLoader/**ClassLoader 没有特别处理 拿默认即可 **/,

     // Class<?>[]/**代理接口类**/, InvocationHandler /**代理处理逻辑**/)

     UserService proxy = (UserService) Proxy.newProxyInstance(TestProxy.class.getClassLoader(), new Class[] { UserService.class }, handler);

     run("jdk", proxy);

     }

     public static void testNative() {

     UserService impTarget = new UserServiceImpl();

     run("native", impTarget);

     }

     private static void run(String tag, UserService impTarget) {

     int c = 15;

     System.out.println();

     while (c-- > 0) {

         long start = System.currentTimeMillis();

         for (int i = 0; i < 10000000; i++) {

         impTarget.getName(11);

         }

         long end = System.currentTimeMillis();

         System.out.print(tag + ": " + (end - start) + " ");

     }

     }

 }

运行结果:

native: 175 native: 182 native: 126 native: 172 native: 126 native: 127 native: 127 native: 126 native: 127 native: 126 native: 126 native: 128 native: 126 native: 127 native: 126
jdk: 214 jdk: 170 jdk: 169 jdk: 169 jdk: 170 jdk: 170 jdk: 170 jdk: 170 jdk: 170 jdk: 172 jdk: 169 jdk: 172 jdk: 169 jdk: 171 jdk: 169

先运行预热，看出执行五次之后比较稳定

jdk动态代理使用非常简单，使用Proxy.newProxyInstance 静态方法即可

接下来我们看下class指令

javac -encoding UTF-8 -d . TestProxy.java

javap -v com\eyu\onequeue\TestProxy.class > s.txt

其中

// Method java/lang/reflect/Proxy.newProxyInstance:(Ljava/lang/ClassLoader;[Ljava/lang/Class;Ljava/lang/reflect/InvocationHandler;)Ljava/lang/Object;

没有详细看到代理类指令

运行时生成的动态代理对象是可以导出到文件的，方法有两种

在代码中加入System.setProperty("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");
在运行时加入jvm 参数 -Dsun.misc.ProxyGenerator.saveGeneratedFiles=true

我们在main方法加一行System.setProperty("sun.misc.ProxyGenerator.saveGeneratedFiles", "true"); 然后执行一下

  public static void main(String[] args) {

     System.setProperty("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");

      //省略

  }

这时在包下会多出$Proxy0.class文件

proxy0.class用jd-gui打开

 package com.sun.proxy;

 import com.eyu.onequeue.TestProxy.UserService;

 import java.lang.reflect.InvocationHandler;

 import java.lang.reflect.Method;

 import java.lang.reflect.Proxy;

 import java.lang.reflect.UndeclaredThrowableException;

 public final class $Proxy0

   extends Proxy

   implements TestProxy.UserService

 {

   private static Method m1;

   private static Method m2;

   private static Method m3;

   private static Method m4;

   private static Method m0;

   public $Proxy0(InvocationHandler paramInvocationHandler)

   {

     super(paramInvocationHandler);

   }

   public final boolean equals(Object paramObject)

   {

     try

     {

       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 String toString()

   {

     try

     {

       return (String)this.h.invoke(this, m2, null);

     }

     catch (Error|RuntimeException localError)

     {

       throw localError;

     }

     catch (Throwable localThrowable)

     {

       throw new UndeclaredThrowableException(localThrowable);

     }

   }

   public final String getName(int paramInt)

   {

     try

     {

       return (String)this.h.invoke(this, m3, new Object[] { Integer.valueOf(paramInt) });

     }

     catch (Error|RuntimeException localError)

     {

       throw localError;

     }

     catch (Throwable localThrowable)

     {

       throw new UndeclaredThrowableException(localThrowable);

     }

   }

   public final Integer getAge(int paramInt)

   {

     try

     {

       return (Integer)this.h.invoke(this, m4, new Object[] { Integer.valueOf(paramInt) });

     }

     catch (Error|RuntimeException localError)

     {

       throw localError;

     }

     catch (Throwable localThrowable)

     {

       throw new UndeclaredThrowableException(localThrowable);

     }

   }

   public final int hashCode()

   {

     try

     {

       return ((Integer)this.h.invoke(this, m0, null)).intValue();

     }

     catch (Error|RuntimeException localError)

     {

       throw localError;

     }

     catch (Throwable localThrowable)

     {

       throw new UndeclaredThrowableException(localThrowable);

     }

   }

   static

   {

     try

     {

       m1 = Class.forName("java.lang.Object").getMethod("equals", new Class[] { Class.forName("java.lang.Object") });

       m2 = Class.forName("java.lang.Object").getMethod("toString", new Class[0]);

       m3 = Class.forName("com.eyu.onequeue.TestProxy$UserService").getMethod("getName", new Class[] { Integer.TYPE });

       m4 = Class.forName("com.eyu.onequeue.TestProxy$UserService").getMethod("getAge", new Class[] { Integer.TYPE });

       m0 = Class.forName("java.lang.Object").getMethod("hashCode", new Class[0]);

       return;

     }

     catch (NoSuchMethodException localNoSuchMethodException)

     {

       throw new NoSuchMethodError(localNoSuchMethodException.getMessage());

     }

     catch (ClassNotFoundException localClassNotFoundException)

     {

       throw new NoClassDefFoundError(localClassNotFoundException.getMessage());

     }

   }

 }

proxy0

proxy0分析分两部份

1.在内存动态生成代理类以$proxy 开头

$Proxy0 extends Proxy implements XXXXProxy.UserService

并初始化InvocationHandler 同绑定 Method

 public $Proxy0(InvocationHandler paramInvocationHandler)

 {

 　　super(paramInvocationHandler);

 }

 static

 {

 try

 {

 　　m1 = Class.forName("java.lang.Object").getMethod("equals", new Class[] { Class.forName("java.lang.Object") });

 　　m2 = Class.forName("java.lang.Object").getMethod("toString", new Class[0]);

 　　m3 = Class.forName("com.eyu.onequeue.TestProxy$UserService").getMethod("getName", new Class[] { Integer.TYPE });

 　　m4 = Class.forName("com.eyu.onequeue.TestProxy$UserService").getMethod("getAge", new Class[] { Integer.TYPE });

 　　m0 = Class.forName("java.lang.Object").getMethod("hashCode", new Class[0]);

 　　return;

 }

 .....

 }

第二部分：代理原对象所有方法实现调用InvocationHandler 类的 Object invoke(Object target, Method method, Object[] args) throws Throwable 方法再通过method反射invoke

public final String getName(int paramInt)

{

try

{

    return (String)this.h.invoke(this, m3, new Object[] { Integer.valueOf(paramInt) });

}

catch (Error|RuntimeException localError)

{

    throw localError;

}

catch (Throwable localThrowable)

{

    throw new UndeclaredThrowableException(localThrowable);

}

}

我们通过生成指令 E:\java\findme\com\sun\proxy>javap -v $Proxy0.class > d.txt

来查看代理过的getName方法共多少条指令

  public final java.lang.String getName(int) throws ;

    descriptor: (I)Ljava/lang/String;

    flags: ACC_PUBLIC, ACC_FINAL

    Code:

      stack=10, locals=3, args_size=2

         0: aload_0

         1: getfield      #16                 // Field java/lang/reflect/Proxy.h:Ljava/lang/reflect/InvocationHandler;

         4: aload_0

         5: getstatic     #57                 // Field m3:Ljava/lang/reflect/Method;

         8: iconst_1

         9: anewarray     #22                 // class java/lang/Object

        12: dup

        13: iconst_0

        14: iload_1

        15: invokestatic  #63                 // Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer;

        18: aastore

        19: invokeinterface #28,  4           // InterfaceMethod java/lang/reflect/InvocationHandler.invoke:(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;)Ljava/lang/Object;

        24: checkcast     #52                 // class java/lang/String

        27: areturn

        28: athrow

        29: astore_2

        30: new           #42                 // class java/lang/reflect/UndeclaredThrowableException

        33: dup

        34: aload_2

        35: invokespecial #45                 // Method java/lang/reflect/UndeclaredThrowableException."<init>":(Ljava/lang/Throwable;)V

        38: athrow

      Exception table:

         from    to  target type

             0    28    28   Class java/lang/Error

             0    28    28   Class java/lang/RuntimeException

             0    28    29   Class java/lang/Throwable

    Exceptions:

      throws

如果不出错，到 27：areturn 至少要执行到13条指令 java8对动态代理有优化过

结论是:jdk动态代理比原生调用只慢几十毫秒，这点可以忽略不计

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