JDK中注解的底层实现(4)

public static void main(String[] args) throws Exception {
        System.setProperty("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");
        Counter counter = Main.class.getAnnotation(Counter.class);
        System.out.println(counter.count());
    }

执行完毕之后，项目中多了一个目录：

其中$Proxy0是@Retention注解对应的动态代理类，而$Proxy1才是我们的@Counter对应的动态代理类，当然如果有更多的注解，那么有可能生成$ProxyN。接着我们直接看$Proxy1的源码：

public final class $Proxy1 extends Proxy implements Counter {
    private static Method m1;
    private static Method m2;
    private static Method m3;
    private static Method m4;
    private static Method m0;

public $Proxy1(InvocationHandler var1) throws  {
        super(var1);
    }

public final boolean equals(Object var1) throws  {
        try {
            return (Boolean)super.h.invoke(this, m1, new Object[]{var1});
        } catch (RuntimeException | Error var3) {
            throw var3;
        } catch (Throwable var4) {
            throw new UndeclaredThrowableException(var4);
        }
    }

public final String toString() throws  {
        try {
            return (String)super.h.invoke(this, m2, (Object[])null);
        } catch (RuntimeException | Error var2) {
            throw var2;
        } catch (Throwable var3) {
            throw new UndeclaredThrowableException(var3);
        }
    }

public final int count() throws  {
        try {
            return (Integer)super.h.invoke(this, m3, (Object[])null);
        } catch (RuntimeException | Error var2) {
            throw var2;
        } catch (Throwable var3) {
            throw new UndeclaredThrowableException(var3);
        }
    }

public final Class annotationType() throws  {
        try {
            return (Class)super.h.invoke(this, m4, (Object[])null);
        } catch (RuntimeException | Error var2) {
            throw var2;
        } catch (Throwable var3) {
            throw new UndeclaredThrowableException(var3);
        }
    }

public final int hashCode() throws  {
        try {
            return (Integer)super.h.invoke(this, m0, (Object[])null);
        } catch (RuntimeException | Error var2) {
            throw var2;
        } catch (Throwable var3) {
            throw new UndeclaredThrowableException(var3);
        }
    }

static {
        try {
            m1 = Class.forName("java.lang.Object").getMethod("equals", Class.forName("java.lang.Object"));
            m2 = Class.forName("java.lang.Object").getMethod("toString");
            m3 = Class.forName("club.throwable.annotation.Counter").getMethod("count");
            m4 = Class.forName("club.throwable.annotation.Counter").getMethod("annotationType");
            m0 = Class.forName("java.lang.Object").getMethod("hashCode");
        } catch (NoSuchMethodException var2) {
            throw new NoSuchMethodError(var2.getMessage());
        } catch (ClassNotFoundException var3) {
            throw new NoClassDefFoundError(var3.getMessage());
        }
    }
}