Hey there! Let's break down your OkHttp Interceptor questions using your code example as a reference—this stuff can feel a bit abstract at first, but it's actually pretty straightforward once you visualize the flow.

1. What is the Chain object in OkHttp Interceptors? #

Think of the Chain as the "traffic controller" for your request pipeline. It's an internal interface within the Interceptor class that handles three core jobs:

• Holds the current request moving through the sequence of interceptors
• Knows which interceptor comes next (or triggers the actual network call if it's the last in line)
• Gives you access to context details like request timeouts, connection info, and more

Interceptors work in a sequential "chain" (hence the name)—each one receives a Chain instance, tweaks the request or response, and passes it along. The Chain is what makes this ordered processing possible.

2. What does Request original = chain.request() do? #

This line grabs the raw, unmodified (or pre-tweaked by earlier interceptors) request from the chain. Since OkHttp's Request objects are immutable (you can't edit them directly), you need this original instance as a starting point to build your customized request.

In your code, you'd use this original request to spin up a new builder, add headers, adjust parameters, or make any other changes before sending the request forward.

3. What does return chain.proceed(request) do? #

This is the "go signal" for your request. When you call chain.proceed(request), you're passing your (possibly modified) request to the next interceptor in the chain. If there are no more interceptors left, this method triggers the actual network call to your server.

Once the response comes back—either from the next interceptor or the server—it travels back up the chain. You can optionally modify that response before returning it to the caller. If you skip calling proceed(), your request will never get sent—so this line is mandatory for the request to complete.

Quick Example Walkthrough #

Here's your code snippet expanded to show the full flow:

OkHttpClient.Builder httpClient = new OkHttpClient.Builder();
httpClient.addInterceptor(new Interceptor() {
    @Override
    public Response intercept(Interceptor.Chain chain) throws IOException {
        // Step 1: Grab the original request from the chain
        Request original = chain.request();
        
        // Step 2: Customize the request (add headers here)
        Request modifiedRequest = original.newBuilder()
                .addHeader("Authorization", "Bearer your-auth-token")
                .addHeader("Content-Type", "application/json")
                .build();
        
        // Step 3: Pass the modified request to the next step in the chain
        Response response = chain.proceed(modifiedRequest);
        
        // Optional: Modify the response before returning it
        Response modifiedResponse = response.newBuilder()
                .addHeader("X-Custom-Header", "intercepted-response")
                .build();
        
        // Return the final response to the caller
        return modifiedResponse;
    }
});

内容的提问来源于stack exchange，提问作者Nikolas Bozic