Call Stack

at net.sf.cglib.core.CodeEmitter.visitMaxs(CodeEmitter.java:842)
at net.sf.cglib.core.CodeEmitter.end_method(CodeEmitter.java:138)
at net.sf.cglib.proxy.Enhancer.emitMethods(Enhancer.java:1230)
at net.sf.cglib.proxy.Enhancer.generateClass(Enhancer.java:630)
at net.sf.cglib.core.DefaultGeneratorStrategy.generate(DefaultGeneratorStrategy.java:25)
at net.sf.cglib.core.AbstractClassGenerator.generate(AbstractClassGenerator.java:329)
at net.sf.cglib.proxy.Enhancer.generate(Enhancer.java:492)
at net.sf.cglib.core.AbstractClassGenerator$ClassLoaderData$3.apply(AbstractClassGenerator.java:93)
at net.sf.cglib.core.AbstractClassGenerator$ClassLoaderData$3.apply(AbstractClassGenerator.java:91)
at net.sf.cglib.core.internal.LoadingCache$2.call(LoadingCache.java:54)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at net.sf.cglib.core.internal.LoadingCache.createEntry(LoadingCache.java:61)
at net.sf.cglib.core.internal.LoadingCache.get(LoadingCache.java:34)
at net.sf.cglib.core.AbstractClassGenerator$ClassLoaderData.get(AbstractClassGenerator.java:116)
at net.sf.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:291)
at net.sf.cglib.proxy.Enhancer.createHelper(Enhancer.java:480)
at net.sf.cglib.proxy.Enhancer.create(Enhancer.java:305)
at basic.ATest.testFixedValue(ATest.java:34)

底层用的是ASM

Enhancer
create()

private Object createHelper() {
        this.preValidate();
        Object key = KEY_FACTORY.newInstance(
            this.superclass != null ? this.superclass.getName() : null, //basic.A
            ReflectUtils.getNames(this.interfaces), //null
            this.filter == ALL_ZERO ? null : new WeakCacheKey(this.filter),//null
            this.callbackTypes, //[Lorg.objectweb.asm.Type;@6b9651f3]
            this.useFactory,//true
            this.interceptDuringConstruction, //true
            this.serialVersionUID//true
        );
        this.currentKey = key;
        Object result = super.create(key);
        return result;
}

this.superclass = basic.A

this.filter=ALL_ZERO=

new CallbackFilter() {
    public int accept(Method method) {
        return 0;
    }
};

AbstractClassGenerator.create(Object key)

protected Object create(Object key) {
    try {
        ClassLoader loader = this.getClassLoader();
        Map<ClassLoader, AbstractClassGenerator.ClassLoaderData> cache = CACHE;
        AbstractClassGenerator.ClassLoaderData data = (AbstractClassGenerator.ClassLoaderData)cache.get(loader);
        if (data == null) {//这里一般data！=null，所以不走
            Class var5 = AbstractClassGenerator.class;
            synchronized(AbstractClassGenerator.class) {
                cache = CACHE;
                data = (AbstractClassGenerator.ClassLoaderData)cache.get(loader);
                if (data == null) {
                    Map<ClassLoader, AbstractClassGenerator.ClassLoaderData> newCache = new WeakHashMap(cache);
                    data = new AbstractClassGenerator.ClassLoaderData(loader);
                    newCache.put(loader, data);
                    CACHE = newCache;
                }
            }
        }

        this.key = key;
        Object obj = data.get(this, this.getUseCache());
        return obj instanceof Class ? this.firstInstance((Class)obj) : this.nextInstance(obj);
    } catch (RuntimeException var9) {
        throw var9;
    } catch (Error var10) {
        throw var10;
    } catch (Exception var11) {
        throw new CodeGenerationException(var11);
    }
}

AbstractClassGenerator.gen

public Object get(AbstractClassGenerator gen, boolean useCache) {
    if (!useCache) {//这里=true，所以一直走else
        return gen.generate(this);
    } else {
        Object cachedValue = this.generatedClasses.get(gen);
        return gen.unwrapCachedValue(cachedValue);
    }
}

这里只有Object cachedValue = this.generatedClasses.get(gen);最重要，这个get方法如下，其实就是里面维护了个map当cache，cache不命中就this.createEntry(key, cacheKey, v);

public V get(K key) {
    KK cacheKey = this.keyMapper.apply(key);
    Object v = this.map.get(cacheKey);
    return v != null && !(v instanceof FutureTask) ? v : this.createEntry(key, cacheKey, v);
}

一开始进来是关于要创建的class A的，然后走到Object obj = data.get(this, this.getUseCache());的时候recursive call 自己

第一次进来key=net.sf.cglib.core.MethodWrapper$MethodWrapperKey

gen=net.sf.cglib.core.KeyFactory$Generator@27f723

generatedClasses=

1
2

{net.sf.cglib.proxy.Enhancer$EnhancerKey=java.lang.ref.WeakReference@7b69c6ba, basic.A, null, null, {Lnet/sf/cglib/proxy/FixedValue;}, true, true, null=java.util.concurrent.FutureTask@46daef40, 
net.sf.cglib.core.MethodWrapper$MethodWrapperKey=java.lang.ref.WeakReference@12f41634}

返回net.sf.cglib.core.MethodWrapper$MethodWrapperKey$$KeyFactoryByCGLIB$$d45e49f7

第二次进来key=basic.A的一大串，gen=Enhancer,
Enhancer.generateClass

public void generateClass(ClassVisitor v) throws Exception {
     Class sc = this.superclass == null ? Object.class : this.superclass;
     if (TypeUtils.isFinal(sc.getModifiers())) {
         throw new IllegalArgumentException("Cannot subclass final class " + sc.getName());
     } else {
         List constructors = new ArrayList(Arrays.asList(sc.getDeclaredConstructors()));
         this.filterConstructors(sc, constructors);
         List actualMethods = new ArrayList();
         List interfaceMethods = new ArrayList();
         final Set forcePublic = new HashSet();
         getMethods(sc, this.interfaces, actualMethods, interfaceMethods, forcePublic);
         List methods = CollectionUtils.transform(actualMethods, new Transformer() {
             public Object transform(Object value) {
                 Method method = (Method)value;
                 int modifiers = 16 | method.getModifiers() & -1025 & -257 & -33;
                 if (forcePublic.contains(MethodWrapper.create(method))) {
                     modifiers = modifiers & -5 | 1;
                 }

                 return ReflectUtils.getMethodInfo(method, modifiers);
             }
         });
         ClassEmitter e = new ClassEmitter(v);
         if (this.currentData == null) {
             e.begin_class(46, 1, this.getClassName(), Type.getType(sc), this.useFactory ? TypeUtils.add(TypeUtils.getTypes(this.interfaces), FACTORY) : TypeUtils.getTypes(this.interfaces), "<generated>");
         } else {
             e.begin_class(46, 1, this.getClassName(), (Type)null, new Type[]{FACTORY}, "<generated>");
         }

         List constructorInfo = CollectionUtils.transform(constructors, MethodInfoTransformer.getInstance());
         e.declare_field(2, "CGLIB$BOUND", Type.BOOLEAN_TYPE, (Object)null);
         e.declare_field(9, "CGLIB$FACTORY_DATA", OBJECT_TYPE, (Object)null);
         if (!this.interceptDuringConstruction) {
             e.declare_field(2, "CGLIB$CONSTRUCTED", Type.BOOLEAN_TYPE, (Object)null);
         }

         e.declare_field(26, "CGLIB$THREAD_CALLBACKS", THREAD_LOCAL, (Object)null);
         e.declare_field(26, "CGLIB$STATIC_CALLBACKS", CALLBACK_ARRAY, (Object)null);
         if (this.serialVersionUID != null) {
             e.declare_field(26, "serialVersionUID", Type.LONG_TYPE, this.serialVersionUID);
         }

         for(int i = 0; i < this.callbackTypes.length; ++i) {
             e.declare_field(2, getCallbackField(i), this.callbackTypes[i], (Object)null);
         }

         e.declare_field(10, "CGLIB$CALLBACK_FILTER", OBJECT_TYPE, (Object)null);
         if (this.currentData == null) {
             this.emitMethods(e, methods, actualMethods);
             this.emitConstructors(e, constructorInfo);
         } else {
             this.emitDefaultConstructor(e);
         }

         this.emitSetThreadCallbacks(e);
         this.emitSetStaticCallbacks(e);
         this.emitBindCallbacks(e);
         if (this.useFactory || this.currentData != null) {
             int[] keys = this.getCallbackKeys();
             this.emitNewInstanceCallbacks(e);
             this.emitNewInstanceCallback(e);
             this.emitNewInstanceMultiarg(e, constructorInfo);
             this.emitGetCallback(e, keys);
             this.emitSetCallback(e, keys);
             this.emitGetCallbacks(e);
             this.emitSetCallbacks(e);
         }

         e.end_class();
     }
 }

从ClassVisitor名称来看，就是visitor模式，v= DebuggingClassWriter@1014
sc=basic.A
methods 拿到了所有A的方法，包括Object里继承的
methods.toString()=[
test(Ljava/lang/String;)Ljava/lang/String;,
test1(Ljava/lang/String;)Ljava/lang/String;,
equals(Ljava/lang/Object;)Z,
toString()Ljava/lang/String;,
hashCode()I,
clone()Ljava/lang/Object;]

ClassEmitter e就是新生成的代理的信息
e.classInfo.toString()=basic.A$$EnhancerByCGLIB$$a593fb86
basic.A$$EnhancerByCGLIB$$a593fb86 extends A
e.fieldInfo={CGLIB$STATIC_CALLBACKS=net.sf.cglib.core.ClassEmitter$FieldInfo@d45d4ff9, CGLIB$CALLBACK_0=net.sf.cglib.core.ClassEmitter$FieldInfo@6cada385, CGLIB$THREAD_CALLBACKS=net.sf.cglib.core.ClassEmitter$FieldInfo@15b3f091, CGLIB$BOUND=net.sf.cglib.core.ClassEmitter$FieldInfo@4050e674, CGLIB$FACTORY_DATA=net.sf.cglib.core.ClassEmitter$FieldInfo@861434f0}

callbackTypes.toString()=[Lorg.objectweb.asm.Type;@50d0686]就是Lnet/sf/cglib/proxy/FixedValue;然后就交给FixedValueGenerator去generate

ASM

ASM的包里面大量应用了visitor模式，visit package, class, field, method, code block, frame, TryCatchBlock, MultiANewArrayInsn, LocalVariable, LineNumber, MaxsEnd, TypeAnnotation, Parameter.反正就是很细
cglib里也有同一套，加了点null判断什么的，然后就调用了ASM对应的visit方法。
参考cglib的MethodVisitorTee和asm的MethodWriter

这些XXWriter里就是直接写字节码的了，充斥了各种ByteArray，还有硬编码的字符

不知道Frame是干什么用的，里面的execute方法很震撼。。。

FJD

CGLib Source Code Read

Call Stack

ASM