Java培训实战教程之将代理对象保存到本地文件

╰半橙微兮° 2023-02-22 07:47 1阅读 0赞

我们知道，在Java中，常用的动态代理技术有JDK的动态代理和cglib动态代理，但是不管是哪种方式，代理对象都是在程序运行时，运用反射机制动态创建而成，而我们并不能直观的看到生成的代理对象对应的Java源代码。下面，我就提供一种方式，可以将通过动态代理创建的代理对象的字节码文件保存到磁盘，再通过反编译工具查看生成文件的内容，这样就可以加深我们对于代理对象的理解。

JDK的动态代理依靠接口实现，如果有些类并没有实现接口，则不能使用JDK代理，这就要使用cglib动态代理了，在此，我们以JDK的动态代理为例。

在JDK中提供了一个ProxyGenerator类，可以将代理对象的字节码得到，我们再通过一个输出流就可以将文件保存到磁盘了。

首先定义一个接口：

public class JdkProxyTest \{

public static void main(String\[\] args) throws Exception \{

final IUserDao target = new UserDaoImpl();

IUserDao proxy = (IUserDao) Proxy.newProxyInstance(target.getClass()

.getClassLoader(), target.getClass().getInterfaces(),

new InvocationHandler() \{

public Object invoke(Object proxy, Method method,

Object\[\] args) throws Throwable \{

System.out.println(method.getName());

return method.invoke(target, args);

\});

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc4MjE0MA_size_16_color_FFFFFF_t_70][]

byte\[\] proxyClass = ProxyGenerator.generateProxyClass(proxy.getClass()

.getSimpleName(), proxy.getClass().getInterfaces());

//将字节码文件保存到D盘，文件名为$Proxy0.class

FileOutputStream outputStream = new FileOutputStream(new File(

d:\\\\$Proxy0.class ));

outputStream.write(proxyClass);

outputStream.flush();

outputStream.close();

import cn.itcast.jdkproxy.IUserDao;

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 IUserDao

private static Method m3;

private static Method m1;

private static Method m0;

private static Method m2;

public $Proxy0(InvocationHandler paramInvocationHandler)

throws

super(paramInvocationHandler);

public final void save()

throws

try

this.h.invoke(this, m3, null);

return;

catch (RuntimeException localRuntimeException)

throw localRuntimeException;

catch (Throwable localThrowable)

throw new UndeclaredThrowableException(localThrowable);

public final boolean equals(Object paramObject)

throws

try

return ((Boolean)this.h.invoke(this, m1, new Object\[\] \{ paramObject \})).booleanValue();

catch (RuntimeException localRuntimeException)

throw localRuntimeException;

catch (Throwable localThrowable)

throw new UndeclaredThrowableException(localThrowable);

[叩丁狼][Link 1]Java培训实战教程之将代理对象保存到本地文件

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc4MjE0MA_size_16_color_FFFFFF_t_70 1][]

public final int hashCode()

throws

try

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

catch (RuntimeException localRuntimeException)

throw localRuntimeException;

catch (Throwable localThrowable)

throw new UndeclaredThrowableException(localThrowable);

public final String toString()

throws

try

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

catch (RuntimeException localRuntimeException)

throw localRuntimeException;

catch (Throwable localThrowable)

throw new UndeclaredThrowableException(localThrowable);

static

try

m3 = Class.forName( cn.itcast.jdkproxy.IUserDao ).getMethod( save , new Class\[0\]);

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

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());

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc4MjE0MA_size_16_color_FFFFFF_t_70 2][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc4MjE0MA_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200702103819978.jpg?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc4MjE0MA==,size_16,color_FFFFFF,t_70
[Link 1]: https://www.wolfcode.cn/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc4MjE0MA_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20200702103840856.jpg?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc4MjE0MA==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc4MjE0MA_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/20200702103908288.jpg?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc4MjE0MA==,size_16,color_FFFFFF,t_70