mybatis中的扩展实现源码解析

public interface Interceptor {
 
 Object intercept(Invocation invocation) throws Throwable;
 
 Object plugin(Object target);
 
 void setProperties(Properties properties);
 
}

public class Plugin implements InvocationHandler {
 
 private final Object target;
 private final Interceptor interceptor;
 private final Map<Class<?>, Set<Method>> signatureMap;
 
 private Plugin(Object target, Interceptor interceptor, Map<Class<?>, Set<Method>> signatureMap) {
 this.target = target;
 this.interceptor = interceptor;
 this.signatureMap = signatureMap;
 }
 
 public static Object wrap(Object target, Interceptor interceptor) {
 Map<Class<?>, Set<Method>> signatureMap = getSignatureMap(interceptor);
 Class<?> type = target.getClass();
 Class<?>[] interfaces = getAllInterfaces(type, signatureMap);
 if (interfaces.length > 0) {
  return Proxy.newProxyInstance(
   type.getClassLoader(),
   interfaces,
   new Plugin(target, interceptor, signatureMap));
 }
 return target;
 }
 
 @Override
 public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
 try {
  Set<Method> methods = signatureMap.get(method.getDeclaringClass());
  if (methods != null && methods.contains(method)) {
  return interceptor.intercept(new Invocation(target, method, args));
  }
  return method.invoke(target, args);
 } catch (Exception e) {
  throw ExceptionUtil.unwrapThrowable(e);
 }
 }
 
 ......
}

public class InterceptorChain {
 
 private final List<Interceptor> interceptors = new ArrayList<Interceptor>();
 
 public Object pluginAll(Object target) {
 for (Interceptor interceptor : interceptors) {
  target = interceptor.plugin(target);
 }
 return target;
 }
 
 public void addInterceptor(Interceptor interceptor) {
 interceptors.add(interceptor);
 }
 
 public List<Interceptor> getInterceptors() {
 return Collections.unmodifiableList(interceptors);
 }
 
}