Spring Core * 的实现代码

1.设计原理

通过JDK的Proxy方式或者CGLIB方式生成代理对象的时候，相关的 * 已经配置到代理对象中去了；
通过 * 回调

JDK * ：代理类和目标类实现了共同的接口，用到InvocationHandler接口。(见下面代码)
CGLIB * ：代理类是目标类的子类，用到MethodInterceptor接口。(见下面代码)

jdk * 是由Java内部的反射机制来实现的；
cglib * 底层则是借助asm来实现的。

jdk （Proxy）

使用了Proxy类的newProxyInstance()方法来创建代理对象

       final UserService target=new UserServiceImpl();
       Class<UserService> clazz = UserService.class;
       ClassLoader loader = clazz.getClassLoader();
       Object proxyInstance = Proxy.newProxyInstance(loader, new Class[]{clazz}, new InvocationHandler() {
           @Override
           public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
               System.out.println("Before...");
               Object result = method.invoke(target, args);
               System.out.println("After...");
               return result;
           }
       });
       UserService service = (UserService) proxyInstance;
       service.getUserInfo();

cglib

动态类对象Enhancer，它是CGLIB的核心类；Enhancer类的setSuperclass()方法来确定目标对象；setCallback()方法添加回调函数。最后通过return 语句将创建的代理类对象返回。intercept()方法会在程序执行目标方法时被调用，方法运行时会执行切面类中的增强方法（前和后）。

       Enhancer enhancer=new Enhancer();
       enhancer.setSuperclass(UserInfo.class);
       enhancer.setCallbacks(new Callback[]{new MethodInterceptor() {
           @Override
           public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
               System.out.println("Before...");
               Object result = methodProxy.invokeSuper(o, objects);
               System.out.println("After...");
               return result;
           }
       }});

UserInfo userInfo = (UserInfo) enhancer.create();
       userInfo.test();

2.ProxyFactory (Spring-Core)

ProxyFactory在生成代理对象之前需要决定到底是使用JDK * 还是CGLIB技术；
getProxy() 返回 CglibAopProxy 或者 JdkDynamicAopProxy

       UserService target=new UserServiceImpl();

ProxyFactory proxyFactory=new ProxyFactory();
       proxyFactory.setTarget(target);

//addAdvice() 添加多个，自动形成责任链
       proxyFactory.addAdvice(new AopMethodAroundAdvice());
       proxyFactory.addAdvice(new AopMethodBeforeAdvice());
       proxyFactory.addAdvice(new AopMethodAfterAdvice());
       proxyFactory.addAdvice(new AopMethodThrowsAdvice());

//Advisor 设置具体 pointCut和  advice
//        proxyFactory.addAdvisor(new AopPointcutAdvisor());

UserService userService = (UserService) proxyFactory.getProxy();
       userService.getUserInfo();
       userService.test();

public Object getProxy() {
return createAopProxy().getProxy();
}

2.1 JdkDynamicAopProxy

final class JdkDynamicAopProxy implements AopProxy, InvocationHandler, Serializable {

@Override
public Object getProxy() {
return getProxy(ClassUtils.getDefaultClassLoader());
}

@Override
public Object getProxy(@Nullable ClassLoader classLoader) {
if (logger.isTraceEnabled()) {
logger.trace("Creating JDK dynamic proxy: " + this.advised.getTargetSource());
}
return Proxy.newProxyInstance(classLoader, this.proxiedInterfaces, this);
}
@Override
@Nullable
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {

...省略...
Object retVal;

if (this.advised.exposeProxy) {
// Make invocation available if necessary.
oldProxy = AopContext.setCurrentProxy(proxy);
setProxyContext = true;
}

// Get as late as possible to minimize the time we "own" the target,
// in case it comes from a pool.
target = targetSource.getTarget();
Class<?> targetClass = (target != null ? target.getClass() : null);

//重点：获取此方法的拦截链
List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);

// Check whether we have any advice. If we don't, we can fallback on direct
// reflective invocation of the target, and avoid creating a MethodInvocation.
if (chain.isEmpty()) {
// We can skip creating a MethodInvocation: just invoke the target directly
// Note that the final invoker must be an InvokerInterceptor so we know it does
// nothing but a reflective operation on the target, and no hot swapping or fancy proxying.
Object[] argsToUse = AopProxyUtils.adaptArgumentsIfNecessary(method, args);
retVal = AopUtils.invokeJoinpointUsingReflection(target, method, argsToUse);
}
else {
// We need to create a method invocation...
MethodInvocation invocation =
new ReflectiveMethodInvocation(proxy, target, method, args, targetClass, chain);
// Proceed to the joinpoint through the interceptor chain.
retVal = invocation.proceed();
}

// Massage return value if necessary.
Class<?> returnType = method.getReturnType();
if (retVal != null && retVal == target &&
returnType != Object.class && returnType.isInstance(proxy) &&
!RawTargetAccess.class.isAssignableFrom(method.getDeclaringClass())) {
// Special case: it returned "this" and the return type of the method
// is type-compatible. Note that we can't help if the target sets
// a reference to itself in another returned object.
retVal = proxy;
}
else if (retVal == null && returnType != Void.TYPE && returnType.isPrimitive()) {
throw new AopInvocationException(
"Null return value from advice does not match primitive return type for: " + method);
}
return retVal;
}
finally {
if (target != null && !targetSource.isStatic()) {
// Must have come from TargetSource.
targetSource.releaseTarget(target);
}
if (setProxyContext) {
// Restore old proxy.
AopContext.setCurrentProxy(oldProxy);
}
}
}

2.2 CglibAopProxy

class CglibAopProxy implements AopProxy, Serializable {

@Override
public Object getProxy() {
return getProxy(null);
}

@Override
public Object getProxy(@Nullable ClassLoader classLoader) {
if (logger.isTraceEnabled()) {
logger.trace("Creating CGLIB proxy: " + this.advised.getTargetSource());
}

try {
Class<?> rootClass = this.advised.getTargetClass();
Assert.state(rootClass != null, "Target class must be available for creating a CGLIB proxy");

Class<?> proxySuperClass = rootClass;
if (rootClass.getName().contains(ClassUtils.CGLIB_CLASS_SEPARATOR)) {
proxySuperClass = rootClass.getSuperclass();
Class<?>[] additionalInterfaces = rootClass.getInterfaces();
for (Class<?> additionalInterface : additionalInterfaces) {
this.advised.addInterface(additionalInterface);
}
}

// Validate the class, writing log messages as necessary.
validateClassIfNecessary(proxySuperClass, classLoader);

// Configure CGLIB Enhancer...
Enhancer enhancer = createEnhancer();
if (classLoader != null) {
enhancer.setClassLoader(classLoader);
if (classLoader instanceof SmartClassLoader &&
((SmartClassLoader) classLoader).isClassReloadable(proxySuperClass)) {
enhancer.setUseCache(false);
}
}
enhancer.setSuperclass(proxySuperClass);
enhancer.setInterfaces(AopProxyUtils.completeProxiedInterfaces(this.advised));
enhancer.setNamingPolicy(SpringNamingPolicy.INSTANCE);
enhancer.setStrategy(new ClassLoaderAwareGeneratorStrategy(classLoader));

//重点：设置Callbacks[]
Callback[] callbacks = getCallbacks(rootClass);
Class<?>[] types = new Class<?>[callbacks.length];
for (int x = 0; x < types.length; x++) {
types[x] = callbacks[x].getClass();
}
// fixedInterceptorMap only populated at this point, after getCallbacks call above
enhancer.setCallbackFilter(new ProxyCallbackFilter(
this.advised.getConfigurationOnlyCopy(), this.fixedInterceptorMap, this.fixedInterceptorOffset));
enhancer.setCallbackTypes(types);

// Generate the proxy class and create a proxy instance.
return createProxyClassAndInstance(enhancer, callbacks);
}
catch (CodeGenerationException | IllegalArgumentException ex) {
throw new AopConfigException("Could not generate CGLIB subclass of " + this.advised.getTargetClass() +
": Common causes of this problem include using a final class or a non-visible class",
ex);
}
catch (Throwable ex) {
// TargetSource.getTarget() failed
throw new AopConfigException("Unexpected AOP exception", ex);
}
}

//获取Callbacks[]
private Callback[] getCallbacks(Class<?> rootClass) throws Exception {
// Parameters used for optimization choices...
boolean exposeProxy = this.advised.isExposeProxy();
boolean isFrozen = this.advised.isFrozen();
boolean isStatic = this.advised.getTargetSource().isStatic();

// Choose an "aop" interceptor (used for AOP calls). (重要类)
Callback aopInterceptor = new DynamicAdvisedInterceptor(this.advised);

// Choose a "straight to target" interceptor. (used for calls that are
// unadvised but can return this). May be required to expose the proxy.
Callback targetInterceptor;
if (exposeProxy) {
targetInterceptor = (isStatic ?
new StaticUnadvisedExposedInterceptor(this.advised.getTargetSource().getTarget()) :
new DynamicUnadvisedExposedInterceptor(this.advised.getTargetSource()));
}
else {
targetInterceptor = (isStatic ?
new StaticUnadvisedInterceptor(this.advised.getTargetSource().getTarget()) :
new DynamicUnadvisedInterceptor(this.advised.getTargetSource()));
}

// Choose a "direct to target" dispatcher (used for
// unadvised calls to static targets that cannot return this).
Callback targetDispatcher = (isStatic ?
new StaticDispatcher(this.advised.getTargetSource().getTarget()) : new SerializableNoOp());

Callback[] mainCallbacks = new Callback[] {
aopInterceptor,  // for normal advice
targetInterceptor,  // invoke target without considering advice, if optimized
new SerializableNoOp(),  // no override for methods mapped to this
targetDispatcher, this.advisedDispatcher,
new EqualsInterceptor(this.advised),
new HashCodeInterceptor(this.advised)
};

Callback[] callbacks;
...省略...
return callbacks;
}

DynamicAdvisedInterceptor

private static class DynamicAdvisedInterceptor implements MethodInterceptor, Serializable {

private final AdvisedSupport advised;

public DynamicAdvisedInterceptor(AdvisedSupport advised) {
this.advised = advised;
}

@Override
@Nullable
public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
Object oldProxy = null;
boolean setProxyContext = false;
Object target = null;
TargetSource targetSource = this.advised.getTargetSource();
try {
if (this.advised.exposeProxy) {
// Make invocation available if necessary.
oldProxy = AopContext.setCurrentProxy(proxy);
setProxyContext = true;
}
// Get as late as possible to minimize the time we "own" the target, in case it comes from a pool...
target = targetSource.getTarget();
Class<?> targetClass = (target != null ? target.getClass() : null);
//重点：获取此方法的拦截链
List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);
Object retVal;
// Check whether we only have one InvokerInterceptor: that is,
// no real advice, but just reflective invocation of the target.
if (chain.isEmpty() && Modifier.isPublic(method.getModifiers())) {
// We can skip creating a MethodInvocation: just invoke the target directly.
// Note that the final invoker must be an InvokerInterceptor, so we know
// it does nothing but a reflective operation on the target, and no hot
// swapping or fancy proxying.
Object[] argsToUse = AopProxyUtils.adaptArgumentsIfNecessary(method, args);
retVal = methodProxy.invoke(target, argsToUse);
}
else {
// We need to create a method invocation...
retVal = new CglibMethodInvocation(proxy, target, method, args, targetClass, chain, methodProxy).proceed();
}
retVal = processReturnType(proxy, target, method, retVal);
return retVal;
}
finally {
if (target != null && !targetSource.isStatic()) {
targetSource.releaseTarget(target);
}
if (setProxyContext) {
// Restore old proxy.
AopContext.setCurrentProxy(oldProxy);
}
}
}
}

2.3 主要源码部分

public class AdvisedSupport extends ProxyConfig implements Advised {

public List<Object> getInterceptorsAndDynamicInterceptionAdvice(Method method, @Nullable Class<?> targetClass) {
MethodCacheKey cacheKey = new MethodCacheKey(method);
List<Object> cached = this.methodCache.get(cacheKey);
if (cached == null) {
cached = this.advisorChainFactory.getInterceptorsAndDynamicInterceptionAdvice(
this, method, targetClass);
this.methodCache.put(cacheKey, cached);
}
return cached;
}

DefaultAdvisorChainFactory

public class DefaultAdvisorChainFactory implements AdvisorChainFactory, Serializable {

@Override
public List<Object> getInterceptorsAndDynamicInterceptionAdvice(
Advised config, Method method, @Nullable Class<?> targetClass) {

// This is somewhat tricky... We have to process introductions first,
// but we need to preserve order in the ultimate list.
AdvisorAdapterRegistry registry = GlobalAdvisorAdapterRegistry.getInstance();
Advisor[] advisors = config.getAdvisors();
List<Object> interceptorList = new ArrayList<>(advisors.length);
Class<?> actualClass = (targetClass != null ? targetClass : method.getDeclaringClass());
Boolean hasIntroductions = null;

for (Advisor advisor : advisors) {
if (advisor instanceof PointcutAdvisor) {
// Add it conditionally.
PointcutAdvisor pointcutAdvisor = (PointcutAdvisor) advisor;
if (config.isPreFiltered() || pointcutAdvisor.getPointcut().getClassFilter().matches(actualClass)) {
MethodMatcher mm = pointcutAdvisor.getPointcut().getMethodMatcher();
boolean match;
if (mm instanceof IntroductionAwareMethodMatcher) {
if (hasIntroductions == null) {
hasIntroductions = hasMatchingIntroductions(advisors, actualClass);
}
match = ((IntroductionAwareMethodMatcher) mm).matches(method, actualClass, hasIntroductions);
}
else {
match = mm.matches(method, actualClass);
}
if (match) {
//重点：将advisor中的advice转换为MethodInterceptor。
MethodInterceptor[] interceptors = registry.getInterceptors(advisor);
if (mm.isRuntime()) {
// Creating a new object instance in the getInterceptors() method
// isn't a problem as we normally cache created chains.
for (MethodInterceptor interceptor : interceptors) {
interceptorList.add(new InterceptorAndDynamicMethodMatcher(interceptor, mm));
}
}
else {
interceptorList.addAll(Arrays.asList(interceptors));
}
}
}
}
else if (advisor instanceof IntroductionAdvisor) {
IntroductionAdvisor ia = (IntroductionAdvisor) advisor;
if (config.isPreFiltered() || ia.getClassFilter().matches(actualClass)) {
Interceptor[] interceptors = registry.getInterceptors(advisor);
interceptorList.addAll(Arrays.asList(interceptors));
}
}
else {
Interceptor[] interceptors = registry.getInterceptors(advisor);
interceptorList.addAll(Arrays.asList(interceptors));
}
}

return interceptorList;
}

DefaultAdvisorAdapterRegistry

构造方法注册了 MethodBeforeAdviceAdapter、AfterReturningAdviceAdapter、ThrowsAdviceAdapter 3个Adapter模板
通过getInterceptors(Advisor advisor) 方法，将 Advisor 总的advice 转换成 MethodInterceptor

public class DefaultAdvisorAdapterRegistry implements AdvisorAdapterRegistry, Serializable {

private final List<AdvisorAdapter> adapters = new ArrayList<>(3);

/**
* Create a new DefaultAdvisorAdapterRegistry, registering well-known adapters.
*/
public DefaultAdvisorAdapterRegistry() {
registerAdvisorAdapter(new MethodBeforeAdviceAdapter());
registerAdvisorAdapter(new AfterReturningAdviceAdapter());
registerAdvisorAdapter(new ThrowsAdviceAdapter());
}

...省略...
@Override
public MethodInterceptor[] getInterceptors(Advisor advisor) throws UnknownAdviceTypeException {
List<MethodInterceptor> interceptors = new ArrayList<>(3);
Advice advice = advisor.getAdvice();
if (advice instanceof MethodInterceptor) {
interceptors.add((MethodInterceptor) advice);
}
for (AdvisorAdapter adapter : this.adapters) {
if (adapter.supportsAdvice(advice)) {
interceptors.add(adapter.getInterceptor(advisor));
}
}
if (interceptors.isEmpty()) {
throw new UnknownAdviceTypeException(advisor.getAdvice());
}
return interceptors.toArray(new MethodInterceptor[0]);
}

@Override
public void registerAdvisorAdapter(AdvisorAdapter adapter) {
this.adapters.add(adapter);
}

}

1.AfterReturningAdviceAdapter 通过getInterceptor方法 获取 AfterReturningAdviceInterceptor 过滤器
2. AfterReturningAdviceInterceptor invoke()方法 先执行目标方法，后执行（后置）advice了方法

class AfterReturningAdviceAdapter implements AdvisorAdapter, Serializable {

@Override
public boolean supportsAdvice(Advice advice) {
return (advice instanceof AfterReturningAdvice);
}

@Override
public MethodInterceptor getInterceptor(Advisor advisor) {
AfterReturningAdvice advice = (AfterReturningAdvice) advisor.getAdvice();
return new AfterReturningAdviceInterceptor(advice);
}

}

public class AfterReturningAdviceInterceptor implements MethodInterceptor, AfterAdvice, Serializable {

private final AfterReturningAdvice advice;

/**
* Create a new AfterReturningAdviceInterceptor for the given advice.
* @param advice the AfterReturningAdvice to wrap
*/
public AfterReturningAdviceInterceptor(AfterReturningAdvice advice) {
Assert.notNull(advice, "Advice must not be null");
this.advice = advice;
}

@Override
@Nullable
public Object invoke(MethodInvocation mi) throws Throwable {
Object retVal = mi.proceed();
this.advice.afterReturning(retVal, mi.getMethod(), mi.getArguments(), mi.getThis());
return retVal;
}

}

来源：https://blog.csdn.net/qq_18398239/article/details/120822558