获取requestBody异步问题

对接TMS时候，TMS的验签规则是对requestBody的内容进行加密。  
## 1.现象
实现代码如下  
```
@Override
protected Mono<Void> doExecute(ServerWebExchange exchange, ShenyuPluginChain chain, SelectorData selector, RuleData ruleData) {
	LOGGER.debug(".......... TmsSignaturePlugin start..............");
	TmsSignSelectorHandle tmsSignSelectorHandle = TmsSignPluginSelectorDataHandler.CACHED_HANDLE.get().obtainHandle(CacheKeyUtils.INST.getKey(selector));
	if (Objects.isNull(tmsSignSelectorHandle)) {
		LOGGER.error("eaalogin handler can not configuration：{}", tmsSignSelectorHandle);
		return chain.execute(exchange);
	}
	String requestUrl = exchange.getRequest().getPath().toString();
	String apiCode = requestUrl.substring(requestUrl.lastIndexOf("/")+1);
	List<HttpMessageReader<?>> MESSAGE_READERS = HandlerStrategies.builder().build().messageReaders();
	ServerRequest serverRequest = ServerRequest.create(exchange, MESSAGE_READERS);

StringBuilder requestBody =new StringBuilder();
	Mono<String> mono = serverRequest.bodyToMono(String.class).switchIfEmpty(Mono.defer(() -> Mono.just(""))).flatMap(originalBody -> {
		LOGGER.info("get body data success data:{}", originalBody);
		requestBody.append(originalBody);
		return Mono.just(originalBody);
	});
	BodyInserter<Mono<String>, ReactiveHttpOutputMessage> bodyInserter = BodyInserters.fromPublisher(mono, String.class);
	HttpHeaders headers = new HttpHeaders();
	headers.putAll(exchange.getRequest().getHeaders());
	headers.remove(HttpHeaders.CONTENT_LENGTH);
	//tms need header
	long timestamp = System.currentTimeMillis();
	StringBuilder builder = new StringBuilder();
	builder.append("apiCode").append(apiCode);
	builder.append("appKey").append(tmsSignSelectorHandle.getAppKey());
	builder.append("clientId").append(tmsSignSelectorHandle.getClientId());
	builder.append("version").append(version);
	builder.append("timestamp").append(timestamp);
	builder.append("content").append(requestBody);
	builder.append(tmsSignSelectorHandle.getSecret());
	String signTmp = builder.toString();
	String sign = Md5Utils.getMd5Code(signTmp);
	headers.set("sign",sign);
	headers.set("appKey",tmsSignSelectorHandle.getAppKey());
	headers.set("timestamp",String.valueOf(timestamp));
	headers.set("version",TmsSignaturePlugin.version);
	headers.set("clientId",tmsSignSelectorHandle.getClientId());
	CachedBodyOutputMessage outputMessage = new CachedBodyOutputMessage(exchange, headers);
	return bodyInserter.insert(outputMessage, new BodyInserterContext())
			.then(Mono.defer(() -> {
				ServerHttpRequestDecorator decorator = new ModifyServerHttpRequestDecorator(headers, exchange.getRequest(), outputMessage);
				return chain.execute(exchange.mutate().request(decorator).build());
			})).onErrorResume(error -> {
				if (error instanceof ResponsiveException) {
					return WebFluxResultUtils.failedResult((ResponsiveException) error);
				}
				return Mono.error(error);
			});
}
```
解读如下：  
![](/media/202308/2023-08-01_162951_791193.png)
实际运行过程中，发现这段代码是异步的  
```
        Mono<String> mono = serverRequest.bodyToMono(String.class).switchIfEmpty(Mono.defer(() -> Mono.just(""))).flatMap(originalBody -> {
            LOGGER.info("get body data success data:{}", originalBody);
            requestBody.append(originalBody);
            return Mono.just(originalBody);
        });
```
即下面的代码  
```
builder.append("content").append(requestBody);
```
这里用于加密的requestBody是空值。导致TMS验签一直没有通过。
## 2.解决方案
代码如下  
```
    @Override
    protected Mono<Void> doExecute(ServerWebExchange exchange, ShenyuPluginChain chain, SelectorData selector, RuleData ruleData) {
        LOGGER.debug(".......... TmsSignaturePlugin start..............");
        TmsSignSelectorHandle tmsSignSelectorHandle = TmsSignPluginSelectorDataHandler.CACHED_HANDLE.get().obtainHandle(CacheKeyUtils.INST.getKey(selector));
        if (Objects.isNull(tmsSignSelectorHandle)) {
            LOGGER.error("eaalogin handler can not configuration：{}", tmsSignSelectorHandle);
            return chain.execute(exchange);
        }
        String requestUrl = exchange.getRequest().getPath().toString();
        String apiCode = requestUrl.substring(requestUrl.lastIndexOf("/")+1);
        List<HttpMessageReader<?>> MESSAGE_READERS = HandlerStrategies.builder().build().messageReaders();
        ServerRequest serverRequest = ServerRequest.create(exchange, MESSAGE_READERS);

StringBuilder requestBody =new StringBuilder();
        Mono<String> mono = serverRequest.bodyToMono(String.class).switchIfEmpty(Mono.defer(() -> Mono.just(""))).flatMap(originalBody -> {
            LOGGER.info("get body data success data:{}", originalBody);
            requestBody.append(originalBody);
            return Mono.just(originalBody);
        });
        BodyInserter<Mono<String>, ReactiveHttpOutputMessage> bodyInserter = BodyInserters.fromPublisher(mono, String.class);
        HttpHeaders headers = new HttpHeaders();
        headers.putAll(exchange.getRequest().getHeaders());
        headers.remove(HttpHeaders.CONTENT_LENGTH);
        CachedBodyOutputMessage outputMessage = new CachedBodyOutputMessage(exchange, headers);
        return bodyInserter.insert(outputMessage, new BodyInserterContext())
                .then(Mono.defer(() -> {
                    //tms need header
                    long timestamp = System.currentTimeMillis();
                    StringBuilder builder = new StringBuilder();
                    builder.append("apiCode").append(apiCode);
                    builder.append("appKey").append(tmsSignSelectorHandle.getAppKey());
                    builder.append("clientId").append(tmsSignSelectorHandle.getClientId());
                    builder.append("version").append(version);
                    builder.append("timestamp").append(timestamp);
                    builder.append("content").append(requestBody);
                    builder.append(tmsSignSelectorHandle.getSecret());
                    String signTmp = builder.toString();
                    String sign = Md5Utils.getMd5Code(signTmp);
                    headers.set("sign",sign);
                    headers.set("appKey",tmsSignSelectorHandle.getAppKey());
                    headers.set("timestamp",String.valueOf(timestamp));
                    headers.set("version",TmsSignaturePlugin.version);
                    headers.set("clientId",tmsSignSelectorHandle.getClientId());
                    ServerHttpRequestDecorator decorator = new ModifyServerHttpRequestDecorator(headers, exchange.getRequest(), outputMessage);
                    return chain.execute(exchange.mutate().request(decorator).build());
                })).onErrorResume(error -> {
                    if (error instanceof ResponsiveException) {
                        return WebFluxResultUtils.failedResult((ResponsiveException) error);
                    }
                    return Mono.error(error);
                });
    }
```
解读如下：  
![](/media/202308/2023-08-01_163638_967237.png)