Cglib生成的动态代理类源码分析

逃离我推掉我的手 2023-02-24 13:24 14阅读 0赞

代码准备

被代理类Teacher

public class Teacher  \{  
      
    public void say() \{  
        System.out.println(String.join(",","I'm a teacher"));  
    \}  
\}  
自定义的MethodInterceptor

CglibProxy和DefaultProxy

//拦截非Object方法  
public class CglibProxy implements MethodInterceptor \{  
    @Override  
    public Object intercept(Object o, Method method, Object\[\] objects, MethodProxy proxy) throws Throwable \{  
        Object result=null;  
        before();  
        result= proxy.invokeSuper(o,objects);  
        after();  
        return result;  
    \}  
    public Object before()\{  
        System.out.println("before invoke ");  
        return null;  
    \}  
    public Object after()\{  
        System.out.println("after invoke");  
        return null;  
    \}  
\}  
//拦截Object方法  
public class DefaultProxy implements MethodInterceptor \{  
    @Override  
    public Object intercept(Object o, Method method, Object\[\] objects, MethodProxy methodProxy) throws Throwable \{  
        if(method.getDeclaringClass()==Object.class)\{  
            return methodProxy.invokeSuper(o,objects);  
        \}  
        return null;  
    \}  
\}

cglib动态代理使用样列

public class CglibMain \{  
    public static void main(String\[\] args) throws IOException \{  
        Enhancer enhancer=new Enhancer();  
        enhancer.setSuperclass(Teacher.class);  
        enhancer.setCallbacks(new Callback\[\]\{new DefaultProxy(),new CglibProxy()\});  
        enhancer.setCallbackFilter(new MethodFilter());  
        Teacher proxy= (Teacher) enhancer.create();  
        proxy.say();  
    \}  
\}  
上面是cglib动态代理类的使用步骤，具体的运行是什么，我们需要得到enhancer.create()生成的代理类源码，我们可以通过java的HSDB来查看(https://blog.csdn.net/qq\_27378875/article/details/81407989)

\---------------------------------分割线--------------------------------------------

cglib动态类源码分析

1、主要生成了下面两个类：  
cglib动态生成的Teacher的代理类，可以看出extends了Teacher ,所以我们可以用利用多态强转为Teacher

public class Teacher$$EnhancerByCGLIB$$f312f930 extends Teacher implements Factory

cglib动态生成的FastClass，这个会在第7步骤讲解

public class Teacher$$EnhancerByCGLIB$$f312f930$$FastClassByCGLIB$$41d4d523 extends FastClass   
2、

Teacher$$EnhancerByCGLIB$$f312f930的主要参数和方法说明

两个MethodInterceptor是我们自己定义的代理处理类，

private MethodInterceptor CGLIB$CALLBACK\_0; //  
private MethodInterceptor CGLIB$CALLBACK\_1;//我们自己定义的代理处理类，  
//这两个属性通过setCallbacks()来赋值  
 public void setCallbacks(Callback\[\] var1) \{  
        this.CGLIB$CALLBACK\_0 = (MethodInterceptor)var1\[0\];  
        this.CGLIB$CALLBACK\_1 = (MethodInterceptor)var1\[1\];  
 \}  
我们在main方法里调用了 enhancer.setCallbacks(new Callback\[\]\{new DefaultProxy(),new CglibProxy()\});

因此

CGLIB$CALLBACK\_0=new DefaultProxy()；

CGLIB$CALLBACK\_1=new CglibProxy()

Method和MethodProxy（我们现在只分析say()方法，只显示say相关的代码）

private static final Method CGLIB$say$2$Method;//被代理实体类的方法反射类  
private static final MethodProxy CGLIB$say$2$Proxy;//cglib的方法代理类，负责的选择调度，每个方法对应一个MethodProxy，后面详细说明

MethodProxy的初始化，很重要

static void CGLIB$STATICHOOK1() \{  
        CGLIB$THREAD\_CALLBACKS = new ThreadLocal();  
        CGLIB$emptyArgs = new Object\[0\];  
        //cglib代理类  
        Class var0 = Class.forName("com.speedyao.proxy.Teacher$$EnhancerByCGLIB$$f312f930");  
        //在下一行代码可以看出是Object  
        Class var1;  
        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$3$Method = var10000\[0\];  
        CGLIB$finalize$3$Proxy = MethodProxy.create(var1, var0, "()V", "finalize", "CGLIB$finalize$3");  
       
        var10000 = ReflectUtils.findMethods(new String\[\]\{"getName", "()Ljava/lang/String;", "setName", "(Ljava/lang/String;)V", "say", "()V"\}, (var1 =   
        CGLIB$say$2$Method = var10000\[2\];//  
        //这个在下面会用到  
        CGLIB$say$2$Proxy = MethodProxy.create(var1, var0, "()V", "say", "CGLIB$say$2");  
    \}

MethodProxy.create(var1, var0, "()V", "say", "CGLIB$say$2")的方法代码

public static MethodProxy create(Class c1, Class c2, String desc, String name1, String name2) \{  
        MethodProxy proxy = new MethodProxy();  
        proxy.sig1 = new Signature(name1, desc);//say()方法  
        proxy.sig2 = new Signature(name2, desc);//CGLIB$say$2()方法  
        proxy.createInfo = new CreateInfo(c1, c2);  
         return proxy;  
   \}

代理类生成的被代理类相关的方法  
     say()：代理类重写的say方法，当我们用动态代理类执行say()时，执行的就是这段代码

public final void say() \{  
        MethodInterceptor var10000 = this.CGLIB$CALLBACK\_1;  
        if (var10000 == null) \{  
            CGLIB$BIND\_CALLBACKS(this);  
            var10000 = this.CGLIB$CALLBACK\_1;  
        \}  
   
        if (var10000 != null) \{  
            var10000.intercept(this, CGLIB$say$2$Method, CGLIB$emptyArgs, CGLIB$say$2$Proxy);  
        \} else \{  
            super.say();  
        \}  
    \}

CGLIB$say$2()方法，父类是Teacher,所以此方法实际执行的是Teacher.say()

final void CGLIB$say$2() \{  
        super.say();  
    \}  
 3、上面主要参数和方法都罗列完了，接下来开始说明调用细节  
 Teacher proxy= (Teacher) enhancer.create();  
 proxy.say();  
通过上面的say()代码快，我们知道最终执行的是

var10000.intercept(this, CGLIB$say$2$Method, CGLIB$emptyArgs, CGLIB$say$2$Proxy);

由上面的参数分析我们得知var1000=new CglibProxy(),所以这一步就是执行我们自定义的intercept方法

o：是this，也就是动态代理对象  
method:CGLIB$say$2$Method ,也就是Teacher.say()的反射Method类  
objects： CGLIB$emptyArgs，空参数  
proxy：CGLIB$say$2$Proxy，方法代理类  
   
 public Object intercept(Object o, Method method, Object\[\] objects, MethodProxy proxy) throws Throwable \{  
        Object result=null;  
          
        //执行前处理  
        before();  
        //执行被代理类的真实方法  
        result= proxy.invokeSuper(o,objects);  
        //执行后的处理  
        after();  
        return result;  
    \}  
 7、分析proxy.invokeSuper(o,objects)如何触发Teacher.say()

看看proxy.invokeSuper(o,objects)代码

public Object invokeSuper(Object obj, Object\[\] args) throws Throwable \{  
        try \{  
            init();  
            FastClassInfo fci = fastClassInfo;  
            return fci.f2.invoke(fci.i2, obj, args);  
        \} catch (InvocationTargetException e) \{  
            throw e.getTargetException();  
        \}  
    \}

通过代码可以看出最终执行代码是  
fci.f2.invoke(fci.i2, obj, args);  
这行代码关键的两个对象是fci.f2和fci.i2  
查看init()方法

private void init()  
    \{  
   
        if (fastClassInfo == null)  
        \{  
            synchronized (initLock)  
            \{  
                if (fastClassInfo == null)  
                \{  
                    CreateInfo ci = createInfo;  
                    FastClassInfo fci = new FastClassInfo();  
                    fci.f1 = helper(ci, ci.c1);  
                    fci.f2 = helper(ci, ci.c2);  
                    fci.i1 = fci.f1.getIndex(sig1);  
                    fci.i2 = fci.f2.getIndex(sig2);  
                    fastClassInfo = fci;  
                    createInfo = null;  
                \}  
            \}  
        \}  
    \}

通过init()方法，我们得知  
fci.f2=helper(ci, ci.c2);  
fci.i2 = fci.f2.getIndex(sig2);

fci.f2实际上根据com.speedyao.proxy.Teacher$$EnhancerByCGLIB$$f312f930动态生成的FastClass

fci.f2是CGLIB$say$2方法的索引位  
通过下面代码可知上面的结论

static void CGLIB$STATICHOOK1() \{      
        Class var0 = Class.forName("com.speedyao.proxy.Teacher$$EnhancerByCGLIB$$f312f930");  
         CGLIB$say$2$Proxy = MethodProxy.create(var1, var0, "()V", "say", "CGLIB$say$2");  
 \}  
   public static MethodProxy create(Class c1, Class c2, String desc, String name1, String name2) \{  
        MethodProxy proxy = new MethodProxy();  
        proxy.sig1 = new Signature(name1, desc);//say()方法  
        proxy.sig2 = new Signature(name2, desc);//CGLIB$say$2()方法  
        proxy.createInfo = new CreateInfo(c1, c2);  
         return proxy;  
   \}

public class Signature \{  
    private String name;  
    private String desc;  
   
    public Signature(String name, String desc) \{  
        // TODO: better error checking  
        if (name.indexOf('(') >= 0) \{  
            throw new IllegalArgumentException("Name '" + name + "' is invalid");  
        \}  
        this.name = name;  
        this.desc = desc;  
    \}  
   \}

//\*\*  
接下来我们就需要fci.f2.invoke(fci.i2, obj, args)做了什么，fci.f2类型是FastClass的子类，就是我们上面提到的动态生成的Class  
Teacher$$EnhancerByCGLIB$$f312f930$$FastClassByCGLIB$$41d4d523  
反编译的源码如下，只列了关键代码  
\*/  
   
public class Teacher$$EnhancerByCGLIB$$f312f930$$FastClassByCGLIB$$41d4d523 extends FastClass \{  
    public Object invoke(int var1, Object var2, Object\[\] var3) throws InvocationTargetException \{  
        f312f930 var10000 = (f312f930)var2;  
        int var10001 = var1;  
   
        try \{  
            switch(var10001) \{  
            case 0:  
                return new Boolean(var10000.equals(var3\[0\]));       
            case 13:  
                var10000.CGLIB$say$2();  
                return null;  
            case 19:  
                var10000.say();  
                return null;  
     
            \}  
        \} catch (Throwable var4) \{  
            throw new InvocationTargetException(var4);  
        \}  
   
        throw new IllegalArgumentException("Cannot find matching method/constructor");  
    \}  
\}

通过上面的分析我们得知 var1是CGLIB$say$2的index也就是13，var2是Teacher的代理类对象，  
所以实际上执行的代码就是  
var10000.CGLIB$say$2();  
也就是代理类的CGLIB$say$2方法，如下  
 final void CGLIB$say$2() \{  
        super.say();  
  \}  
  因为代理类extends Teacher,所以实际上执行的代码就是Teacher.say()

8、接下来总结下调用步骤

动态代理类  
Teacher$$EnhancerByCGLIB$$f312f930.say()->  
自定义的方法拦截器  
CglibProxy.intercept(this, CGLIB$say$2$Method, CGLIB$emptyArgs, CGLIB$say$2$Proxy)->  
方法代理  
MethodProxy.invokeSuper(o,objects)->  
动态生成的FastClass子类  
Teacher$$EnhancerByCGLIB$$f312f930$$FastClassByCGLIB$$41d4d523.invoke(fci.i2, obj, args)->  
动态代理类  
Teacher$$EnhancerByCGLIB$$f312f930.CGLIB$say$2()->  
被代理对象也就是Teacher  
super.say();

以上便是cglib动态代理类的执行步骤，有什么疑问留言答复，反编译源码需要的话可以留言  
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版权声明：本文为CSDN博主「speedyao」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。  
原文链接：https://blog.csdn.net/u010430495/article/details/98756930