JDK – 动态代理

主要实现 InvocationHandler接口中的invoke 方法

public Object invoke(Object proxy, Method method, Object[] args)
        throws Throwable;

一般开开源大佬写 先判断 方法名，在来个 return method.invoke(getSessionFactory(), args);
兜底。

public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
			try {
				if (method.getName().equals("equals")) {
					// Only consider equal when proxies are identical.
					return (proxy == args[0]);
				}
				else if (method.getName().equals("hashCode")) {
					// Use hashCode of EntityManagerFactory proxy.
					return System.identityHashCode(proxy);
				}
				else if (method.getName().equals("getProperties")) {
					return getProperties();
				}
				else if (method.getName().equals("getWrappedObject")) {
					// Call coming in through InfrastructureProxy interface...
					return getSessionFactory();
				}
				// Regular delegation to the target SessionFactory,
				// enforcing its full initialization...
				return method.invoke(getSessionFactory(), args);
			}
			catch (InvocationTargetException ex) {
				throw ex.getTargetException();
			}
		}

创建代理类的常用方法。就靠这个来创建 类和拦截器的关联。

 - clazz.getClassLoader()    classLoader
 - clazz.getInterfaces()   接口列表
 - XXXInvocationHandler   拦截器。
 return Proxy.newProxyInstance(clazz.getClassLoader(),
                clazz.getInterfaces(),
                XXXInvocationHandler);
                
public static Object newProxyInstance(ClassLoader loader,
                                          Class<?>[] interfaces,
                                          InvocationHandler h)

看几个具体的实现

HystrixInvocationHandler

public Object invoke(final Object proxy, final Method method, final Object[] args)
      throws Throwable {
    // early exit if the invoked method is from java.lang.Object
    // code is the same as ReflectiveFeign.FeignInvocationHandler
    if ("equals".equals(method.getName())) {
      try {
        Object otherHandler =
            args.length > 0 && args[0] != null ? Proxy.getInvocationHandler(args[0]) : null;
        return equals(otherHandler);
      } catch (IllegalArgumentException e) {
        return false;
      }
    } else if ("hashCode".equals(method.getName())) {
      return hashCode();
    } else if ("toString".equals(method.getName())) {
      return toString();
    }

    HystrixCommand<Object> hystrixCommand =
        new HystrixCommand<Object>(setterMethodMap.get(method)) {
          @Override
          protected Object run() throws Exception {
            try {
              return HystrixInvocationHandler.this.dispatch.get(method).invoke(args);
            } catch (Exception e) {
              throw e;
            } catch (Throwable t) {
              throw (Error) t;
            }
          }

          @Override
          protected Object getFallback() {
            if (fallbackFactory == null) {
              return super.getFallback();
            }
            try {
              Object fallback = fallbackFactory.create(getExecutionException());
              Object result = fallbackMethodMap.get(method).invoke(fallback, args);
              if (isReturnsHystrixCommand(method)) {
                return ((HystrixCommand) result).execute();
              } else if (isReturnsObservable(method)) {
                // Create a cold Observable
                return ((Observable) result).toBlocking().first();
              } else if (isReturnsSingle(method)) {
                // Create a cold Observable as a Single
                return ((Single) result).toObservable().toBlocking().first();
              } else if (isReturnsCompletable(method)) {
                ((Completable) result).await();
                return null;
              } else if (isReturnsCompletableFuture(method)) {
                return ((Future) result).get();
              } else {
                return result;
              }
            } catch (IllegalAccessException e) {
              // shouldn't happen as method is public due to being an interface
              throw new AssertionError(e);
            } catch (InvocationTargetException | ExecutionException e) {
              // Exceptions on fallback are tossed by Hystrix
              throw new AssertionError(e.getCause());
            } catch (InterruptedException e) {
              // Exceptions on fallback are tossed by Hystrix
              Thread.currentThread().interrupt();
              throw new AssertionError(e.getCause());
            }
          }
        };

    if (Util.isDefault(method)) {
      return hystrixCommand.execute();
    } else if (isReturnsHystrixCommand(method)) {
      return hystrixCommand;
    } else if (isReturnsObservable(method)) {
      // Create a cold Observable
      return hystrixCommand.toObservable();
    } else if (isReturnsSingle(method)) {
      // Create a cold Observable as a Single
      return hystrixCommand.toObservable().toSingle();
    } else if (isReturnsCompletable(method)) {
      return hystrixCommand.toObservable().toCompletable();
    } else if (isReturnsCompletableFuture(method)) {
      return new ObservableCompletableFuture<>(hystrixCommand);
    }
    return hystrixCommand.execute();
  }

RepositoryInvoker

JPA 的一个接口定义了invokeSave、invokeFindById、invokeFindAll、invokeQueryMethod等等方法。但是没有invoker方法。