Context

Attributes提供了一种向过滤链传递信息的便捷方式，但它们仅影响当前请求。如果您希望传递的信息传播到嵌套的其他请求（例如，通过`flatMap`）或在执行后（例如，通过`concatMap`）传播，那么您需要使用 Reactor Context。

Attributes provide a convenient way to pass information to the filter chain but they only influence the current request. If you want to pass information that propagates to additional requests that are nested, e.g. via flatMap, or executed after, e.g. via concatMap, then you’ll need to use the Reactor Context.

必须在响应链的结尾填充 Reactor Context，以便应用于所有操作。例如：

The Reactor Context needs to be populated at the end of a reactive chain in order to apply to all operations. For example:

Java

WebClient client = WebClient.builder()
		.filter((request, next) ->
				Mono.deferContextual(contextView -> {
					String value = contextView.get("foo");
					// ...
				}))
		.build();

client.get().uri("https://example.org/")
		.retrieve()
		.bodyToMono(String.class)
		.flatMap(body -> {
				// perform nested request (context propagates automatically)...
		})
		.contextWrite(context -> context.put("foo", ...));