Spring WebfluxReactor上下文

Question

>

http://projectreactor.io/docs/core/release/reference/#context

https://jira.spring.io/browse/spr-15680

https://simonbasle.github.io/2018/02/contextual-logging-with-reactor-context-and-mdc/。

import reactor.core.publisher.Mono;
public class Test {

    public static void main(final String[] args) {
        System.out.println(Thread.currentThread().getName()
            + " main "
            + test());
    }

    public static String test() {
        final String key = "message";
        return test1().subscriberContext(ctx -> ctx.put(key, "test")).block();
    }

    public static Mono<String> test1() {
        final String key = "message1";
        return test2().subscriberContext(ctx -> ctx.put(key, "test1 "));
    }

    public static Mono<String> test2() {
        return Mono.just("test2").map(item -> {
            Mono.subscriberContext().map(context -> {
                System.err.println(Thread.currentThread().getName()
                    + " test2 "
                    + context);
                return context;
            });
            return item;
        });
    }}

产出：

main main test2

Answer 1

我想，您希望访问test2()中的订阅者上下文，对吗？只有当您实际上在同一个流中时，这才有效，所以这个片段将修复原始代码：original：

public static Mono<String> test2() {
    return Mono.just("test2").map(item -> {
        // you're creating a new Mono context here, and don't return it/use it anymore
        Mono.subscriberContext().map(context -> {
            System.err.println(Thread.currentThread().getName()
                + " test2 "
                + context);
            return context;
        });
        return item;
    });

修正（尽可能少的改变，可以美化）：

public static Mono<String> test2() {
  return Mono.just("test2").flatMap(item -> { // changed map to flatmap, otherwise would be Mono<Mono<String>> here
    Mono<Context> contextMono = Mono.subscriberContext()
        .map(context -> {
          System.err.println(Thread.currentThread()
                                 .getName() + " test2 " + context);
          return context;
        });
    // let item be returned from "inside" of context Mono
    return contextMono.map(context -> item);
  });

我自己一直都在与subscribercontext作斗争--我发现它不是很清楚，什么时候上下文是按预期使用的，什么时候不是。我希望这能有所帮助。