> For the complete documentation index, see [llms.txt](https://confluxnetwork.gitbook.io/go-conflux-sdk/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://confluxnetwork.gitbook.io/go-conflux-sdk/other/middlewire.md).

# Call/BatchCall RPC Hook

Client composite MiddlewarableMiddle for support setting middleware by `HookCallContext` for hooking `provider.CallContext` method which is the core of all single RPC-related methods. And `HookBatchCallContext` to set middleware for hooking `BatchCallContext`.

For example, we can custom a logger middleware to log for rpc requests.

```
client.HookCallContext(callContextConsoleMiddleware)
```

and the `callContextConsoleMiddleware` implementation is like

```
func callContextConsoleMiddleware(f providers.CallFunc) providers.CallFunc {
	return func(ctx context.Context, resultPtr interface{}, method string, args ...interface{}) error {
		fmt.Printf("request %v %v\n", method, args)
		err := f(ctx, resultPtr, method, args...)
		j, _ := json.Marshal(resultPtr)
		fmt.Printf("response %s\n", j)
		return err
	}
}
```

Also, you could

* customize middleware
* use multiple middlewares

Notice that the middleware chain execution order is like onion, for example, use middleware A first and then middleware B

```go
client.HookCallContext(A)
client.HookCallContext(B)
```

the middleware execution order is

```
A --> B --> client.callRpc --> B --> A
```