通過反編譯後的字節碼理解cglib代理

代碼例子：實驗過程final類不可被代理報錯：Cannot subclass final class class javaDemo.proxyDemo.CGlibTestClass。

另外final方法沒有被代理。

package javaDemo.proxyDemo;

import org.springframework.cglib.proxy.Enhancer;
import org.springframework.cglib.proxy.MethodInterceptor;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;

public class CGlibTestClass {
    public final void test1() {
        System.out.println("hello world test1");
    }

    public void test2() {
        System.out.println("hello world test2");
    }


    public static void main(String[] args) throws Exception {
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(CGlibTestClass.class);
        enhancer.setCallback((MethodInterceptor) (obj, method, args1, proxy) -> {
            System.out.println("before method run...");
            Object result = proxy.invokeSuper(obj, args1);
            System.out.println("after method run...");
            return result;
        });
        CGlibTestClass sample = (CGlibTestClass) enhancer.create();
        sample.test1();
        sample.test2();
        // 獲取代理字節碼文件
        byte[] bytes = enhancer.getStrategy().generate(enhancer);
        File file = new File("./jdk/src/main/java/javaDemo/proxyDemo/CGlibTestClass.class");
        try {
            OutputStream outputStream = new FileOutputStream(file);
            outputStream.write(bytes);
            outputStream.flush();
            outputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

反編譯字節碼如下，實例化創建的代理實例中調用代理方法，執行callback攔截方法intercept，進入代理：

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package $javaDemo.proxyDemo;

import java.lang.reflect.Method;
import javaDemo.proxyDemo.CGlibTestClass;
import org.springframework.cglib.core.ReflectUtils;
import org.springframework.cglib.core.Signature;
import org.springframework.cglib.proxy.Callback;
import org.springframework.cglib.proxy.Factory;
import org.springframework.cglib.proxy.MethodInterceptor;
import org.springframework.cglib.proxy.MethodProxy;

public class CGlibTestClass$$EnhancerByCGLIB$$95b1c7fd extends CGlibTestClass implements Factory {
    private boolean CGLIB$BOUND;
    private static final ThreadLocal CGLIB$THREAD_CALLBACKS;
    private static final Callback[] CGLIB$STATIC_CALLBACKS;
    private MethodInterceptor CGLIB$CALLBACK_0;
    private static final Method CGLIB$test2$0$Method;
    private static final MethodProxy CGLIB$test2$0$Proxy;
    private static final Object[] CGLIB$emptyArgs;
    private static final Method CGLIB$finalize$1$Method;
    private static final MethodProxy CGLIB$finalize$1$Proxy;
    private static final Method CGLIB$equals$2$Method;
    private static final MethodProxy CGLIB$equals$2$Proxy;
    private static final Method CGLIB$toString$3$Method;
    private static final MethodProxy CGLIB$toString$3$Proxy;
    private static final Method CGLIB$hashCode$4$Method;
    private static final MethodProxy CGLIB$hashCode$4$Proxy;
    private static final Method CGLIB$clone$5$Method;
    private static final MethodProxy CGLIB$clone$5$Proxy;

    static void CGLIB$STATICHOOK2() {
        CGLIB$THREAD_CALLBACKS = new ThreadLocal();
        CGLIB$emptyArgs = new Object[0];
        Class var0 = Class.forName("$javaDemo.proxyDemo.CGlibTestClass$$EnhancerByCGLIB$$95b1c7fd");
        Class var1;
        CGLIB$test2$0$Method = ReflectUtils.findMethods(new String[]{"test2", "()V"}, (var1 = Class.forName("javaDemo.proxyDemo.CGlibTestClass")).getDeclaredMethods())[0];
        CGLIB$test2$0$Proxy = MethodProxy.create(var1, var0, "()V", "test2", "CGLIB$test2$0");
        Method[] var10000 = ReflectUtils.findMethods(new String[]{"finalize", "()V", "equals", "(Ljava/lang/Object;)Z", "toString", "()Ljava/lang/String;", "hashCode", "()I", "clone", "()Ljava/lang/Object;"}, (var1 = Class.forName("java.lang.Object")).getDeclaredMethods());
        CGLIB$finalize$1$Method = var10000[0];
        CGLIB$finalize$1$Proxy = MethodProxy.create(var1, var0, "()V", "finalize", "CGLIB$finalize$1");
        CGLIB$equals$2$Method = var10000[1];
        CGLIB$equals$2$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/Object;)Z", "equals", "CGLIB$equals$2");
        CGLIB$toString$3$Method = var10000[2];
        CGLIB$toString$3$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/String;", "toString", "CGLIB$toString$3");
        CGLIB$hashCode$4$Method = var10000[3];
        CGLIB$hashCode$4$Proxy = MethodProxy.create(var1, var0, "()I", "hashCode", "CGLIB$hashCode$4");
        CGLIB$clone$5$Method = var10000[4];
        CGLIB$clone$5$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/Object;", "clone", "CGLIB$clone$5");
    }

    final void CGLIB$test2$0() {
        super.test2();
    }

    public final void test2() {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        if (var10000 != null) {
            var10000.intercept(this, CGLIB$test2$0$Method, CGLIB$emptyArgs, CGLIB$test2$0$Proxy);
        } else {
            super.test2();
        }
    }

    final void CGLIB$finalize$1() throws Throwable {
        super.finalize();
    }

    protected final void finalize() throws Throwable {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        if (var10000 != null) {
            var10000.intercept(this, CGLIB$finalize$1$Method, CGLIB$emptyArgs, CGLIB$finalize$1$Proxy);
        } else {
            super.finalize();
        }
    }

    final boolean CGLIB$equals$2(Object var1) {
        return super.equals(var1);
    }

    public final boolean equals(Object var1) {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        if (var10000 != null) {
            Object var2 = var10000.intercept(this, CGLIB$equals$2$Method, new Object[]{var1}, CGLIB$equals$2$Proxy);
            return var2 == null ? false : (Boolean)var2;
        } else {
            return super.equals(var1);
        }
    }

    final String CGLIB$toString$3() {
        return super.toString();
    }

    public final String toString() {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        return var10000 != null ? (String)var10000.intercept(this, CGLIB$toString$3$Method, CGLIB$emptyArgs, CGLIB$toString$3$Proxy) : super.toString();
    }

    final int CGLIB$hashCode$4() {
        return super.hashCode();
    }

    public final int hashCode() {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        if (var10000 != null) {
            Object var1 = var10000.intercept(this, CGLIB$hashCode$4$Method, CGLIB$emptyArgs, CGLIB$hashCode$4$Proxy);
            return var1 == null ? 0 : ((Number)var1).intValue();
        } else {
            return super.hashCode();
        }
    }

    final Object CGLIB$clone$5() throws CloneNotSupportedException {
        return super.clone();
    }

    protected final Object clone() throws CloneNotSupportedException {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }

        return var10000 != null ? var10000.intercept(this, CGLIB$clone$5$Method, CGLIB$emptyArgs, CGLIB$clone$5$Proxy) : super.clone();
    }

    public static MethodProxy CGLIB$findMethodProxy(Signature var0) {
        String var10000 = var0.toString();
        switch(var10000.hashCode()) {
        case -1574182249:
            if (var10000.equals("finalize()V")) {
                return CGLIB$finalize$1$Proxy;
            }
            break;
        case -1147862635:
            if (var10000.equals("test2()V")) {
                return CGLIB$test2$0$Proxy;
            }
            break;
        case -508378822:
            if (var10000.equals("clone()Ljava/lang/Object;")) {
                return CGLIB$clone$5$Proxy;
            }
            break;
        case 1826985398:
            if (var10000.equals("equals(Ljava/lang/Object;)Z")) {
                return CGLIB$equals$2$Proxy;
            }
            break;
        case 1913648695:
            if (var10000.equals("toString()Ljava/lang/String;")) {
                return CGLIB$toString$3$Proxy;
            }
            break;
        case 1984935277:
            if (var10000.equals("hashCode()I")) {
                return CGLIB$hashCode$4$Proxy;
            }
        }

        return null;
    }

    public CGlibTestClass$$EnhancerByCGLIB$$95b1c7fd() {
        CGLIB$BIND_CALLBACKS(this);
    }

    public static void CGLIB$SET_THREAD_CALLBACKS(Callback[] var0) {
        CGLIB$THREAD_CALLBACKS.set(var0);
    }

    public static void CGLIB$SET_STATIC_CALLBACKS(Callback[] var0) {
        CGLIB$STATIC_CALLBACKS = var0;
    }

    private static final void CGLIB$BIND_CALLBACKS(Object var0) {
        CGlibTestClass$$EnhancerByCGLIB$$95b1c7fd var1 = (CGlibTestClass$$EnhancerByCGLIB$$95b1c7fd)var0;
        if (!var1.CGLIB$BOUND) {
            var1.CGLIB$BOUND = true;
            Object var10000 = CGLIB$THREAD_CALLBACKS.get();
            if (var10000 == null) {
                var10000 = CGLIB$STATIC_CALLBACKS;
                if (var10000 == null) {
                    return;
                }
            }

            var1.CGLIB$CALLBACK_0 = (MethodInterceptor)((Callback[])var10000)[0];
        }

    }

    public Object newInstance(Callback[] var1) {
        CGLIB$SET_THREAD_CALLBACKS(var1);
        CGlibTestClass$$EnhancerByCGLIB$$95b1c7fd var10000 = new CGlibTestClass$$EnhancerByCGLIB$$95b1c7fd();
        CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
        return var10000;
    }

    public Object newInstance(Callback var1) {
        CGLIB$SET_THREAD_CALLBACKS(new Callback[]{var1});
        CGlibTestClass$$EnhancerByCGLIB$$95b1c7fd var10000 = new CGlibTestClass$$EnhancerByCGLIB$$95b1c7fd();
        CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
        return var10000;
    }

    public Object newInstance(Class[] var1, Object[] var2, Callback[] var3) {
        CGLIB$SET_THREAD_CALLBACKS(var3);
        CGlibTestClass$$EnhancerByCGLIB$$95b1c7fd var10000 = new CGlibTestClass$$EnhancerByCGLIB$$95b1c7fd;
        switch(var1.length) {
        case 0:
            var10000.<init>();
            CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
            return var10000;
        default:
            throw new IllegalArgumentException("Constructor not found");
        }
    }

    public Callback getCallback(int var1) {
        CGLIB$BIND_CALLBACKS(this);
        MethodInterceptor var10000;
        switch(var1) {
        case 0:
            var10000 = this.CGLIB$CALLBACK_0;
            break;
        default:
            var10000 = null;
        }

        return var10000;
    }

    public void setCallback(int var1, Callback var2) {
        switch(var1) {
        case 0:
            this.CGLIB$CALLBACK_0 = (MethodInterceptor)var2;
        default:
        }
    }

    public Callback[] getCallbacks() {
        CGLIB$BIND_CALLBACKS(this);
        return new Callback[]{this.CGLIB$CALLBACK_0};
    }

    public void setCallbacks(Callback[] var1) {
        this.CGLIB$CALLBACK_0 = (MethodInterceptor)var1[0];
    }

    static {
        CGLIB$STATICHOOK2();
    }
}