cglib-create分析

Enhancer主要用create创建类

 public void testFixedValue() throws Exception {
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(SampleClass2.class);
        enhancer.setCallback(new FixedValue() {
            public Object loadObject() throws Exception {
                return "Hello cglib!";
            }
        });
        SampleClass2 proxy = (SampleClass2)enhancer.create();
        Assertions.assertEquals("Hello cglib!", proxy.test((String)null));
    }

EnhancerKey初始化：

//初始化父类的基本信息
  private Source source;
  private ClassLoader classLoader;
  private String namePrefix;
//生成内部接口
  private static final EnhancerKey KEY_FACTORY =
      (EnhancerKey)KeyFactory.create(EnhancerKey.class, KeyFactory.HASH_ASM_TYPE, null);

Enchancer的create()调用父类AbstractClassGenerator的create方法

private Object createHelper() {
        preValidate();
        Object key = KEY_FACTORY.newInstance((superclass != null) ? superclass.getName() : null,
                ReflectUtils.getNames(interfaces),
                filter == ALL_ZERO ? null : new WeakCacheKey<CallbackFilter>(filter),
                callbackTypes,
                useFactory,
                interceptDuringConstruction,
                serialVersionUID);
        this.currentKey = key;
        Object result = super.create(key);
        return result;
    }

AbstractClassGenerator的create方法

  protected Object create(Object key) {
        try {
            ClassLoader loader = getClassLoader();
            Map<ClassLoader, ClassLoaderData> cache = CACHE;
            ClassLoaderData data = cache.get(loader);
            if (data == null) {
                synchronized (AbstractClassGenerator.class) {
                    cache = CACHE;
                    data = cache.get(loader);
                    if (data == null) {
                        Map<ClassLoader, ClassLoaderData> newCache = new WeakHashMap<ClassLoader, ClassLoaderData>(cache);
                        data = new ClassLoaderData(loader);
                        newCache.put(loader, data);
                        CACHE = newCache;
                    }
                }
            }
            this.key = key;
            //获取类或方法的弱引用(这是特别关键的一步)
            Object obj = data.get(this, getUseCache());
            if (obj instanceof Class) {
            //初始化类
                return firstInstance((Class) obj);
            }
            //返回方法
            return nextInstance(obj);
        } catch (RuntimeException e) {
            throw e;
        } catch (Error e) {
            throw e;
        } catch (Exception e) {
            throw new CodeGenerationException(e);
        }
    }

data.get(this, getUseCache())调用时序图：