SpringFramework之DefaultAdvisorChainFactory
SpringFramework之DefaultAdvisorChainFactory
Spring版本是5.0.4.release.
JdkDynamicAopProxy中使用到了拦截器链，如下List-1，advised是ProxyFactory，而方法getInterceptorsAndDynamicInterceptionAdvice则是在其父类AdvisedSupport中。
List-1
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
...
// Get the interception chain for this method.
List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);
...
}如下List-2，advisorChainFactory是DefaultAdvisorChainFactory
List-2
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;
}getInterceptorsAndDynamicInterceptionAdvice的方法实现如下List-3所示，会将Advisor转换为Interceptor，List-3中的registry是DefaultAdvisorAdapterRegistry。
List-3
public class DefaultAdvisorChainFactory implements AdvisorChainFactory, Serializable {
@Override
public List<Object> getInterceptorsAndDynamicInterceptionAdvice(
Advised config, Method method, @Nullable Class<?> targetClass) {
...
Interceptor[] interceptors = registry.getInterceptors(advisor);
...
return interceptorList;
}
...如下List-4所示，构造方法中注册了Adapter，而后getInterceptors方法中会使用模板模式将advisor中的advice转换为MethodInterceptor。
List-4
public class DefaultAdvisorAdapterRegistry implements AdvisorAdapterRegistry, Serializable {
private final List<AdvisorAdapter> adapters = new ArrayList<>(3);
public DefaultAdvisorAdapterRegistry() {
registerAdvisorAdapter(new MethodBeforeAdviceAdapter());
registerAdvisorAdapter(new AfterReturningAdviceAdapter());
registerAdvisorAdapter(new ThrowsAdviceAdapter());
}
@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]);
}
...来看个例子，如下List-5所示，MethodBeforeAdviceAdapter的supportsAdvice方法中判断是否是MethodBeforeAdvice；getInterceptor方法中将advice封装到MethodBeforeAdviceInterceptor中。
List-5
class MethodBeforeAdviceAdapter implements AdvisorAdapter, Serializable {
@Override
public boolean supportsAdvice(Advice advice) {
return (advice instanceof MethodBeforeAdvice);
}
@Override
public MethodInterceptor getInterceptor(Advisor advisor) {
MethodBeforeAdvice advice = (MethodBeforeAdvice) advisor.getAdvice();
return new MethodBeforeAdviceInterceptor(advice);
}
}MethodBeforeAdviceInterceptor的代码如下，比较简单，主要是invoke方法，会先调用MethodBeforeAdvice的before方法，之后才会执行MethodInvocation的invoke方法。
List-6
public class MethodBeforeAdviceInterceptor implements MethodInterceptor, BeforeAdvice, Serializable {
private final MethodBeforeAdvice advice;
public MethodBeforeAdviceInterceptor(MethodBeforeAdvice advice) {
Assert.notNull(advice, "Advice must not be null");
this.advice = advice;
}
@Override
public Object invoke(MethodInvocation mi) throws Throwable {
this.advice.before(mi.getMethod(), mi.getArguments(), mi.getThis());
return mi.proceed();
}
}整体来看DefaultAdvisorChainFactory会将我们的advice转换为MethodInerceptor，而不同的Advice实现，对应的MethodInterceptor实现也不一样，进而实现Before、After的拦截实现。
Reference
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