如何在Spring Cloud Gateway中编写用于检查请求主体的自定义GlobalFilter

Question

我想验证GlobalFilter中的主体。

我需要读取两个包含正文校验和的http标头，并将其与正文本身进行比较：

internal class MyFilter : GlobalFilter {
override fun filter(exchange: ServerWebExchange, chain: GatewayFilterChain) =
ByteArrayDecoder()
.decodeToMono(
exchange.request.body,
ResolvableType.forClass(ByteBuffer::class.java),
exchange.request.headers.contentType,
null
)
.flatMap { /* my logic checking body against request headers */ chain.filter(exchange) }
}

问题是decodingToMono阻塞并且不转发请求。

如何正确解码身体？

Answer 1

我成功地编写了一个在读取正文后不会卡住的过滤器：

interface BodyFilter {
fun filter(
body: Mono<ByteArrayResource>,
exchange: ServerWebExchange,
passRequestFunction: () -> Mono<Void>
): Mono<Void>
}
class HeaderAndBodyGlobalFilter(private val bodyFilter: BodyFilter) : GlobalFilter {
private val messageReaders: List<HttpMessageReader<*>> = HandlerStrategies.withDefaults().messageReaders()
override fun filter(exchange: ServerWebExchange, chain: GatewayFilterChain): Mono<Void> {
val serverRequest: ServerRequest = ServerRequest.create(exchange, messageReaders)
val body: Mono<ByteArrayResource> = serverRequest.bodyToMono<ByteArrayResource>(ByteArrayResource::class.java)
return bodyFilter.filter(body, exchange) { reconstructRequest(body, exchange, chain) }
}
private fun reconstructRequest(
body: Mono<ByteArrayResource>,
exchange: ServerWebExchange,
chain: GatewayFilterChain
): Mono<Void> {
val headers: HttpHeaders = writableHttpHeaders(exchange.request.headers)
val outputMessage = CachedBodyOutputMessage(exchange, headers)
return BodyInserters.fromPublisher(
body,
ByteArrayResource::class.java
).insert(outputMessage, BodyInserterContext())
.then(Mono.defer {
val decorator: ServerHttpRequestDecorator = decorate(
exchange, headers, outputMessage
)
chain
.filter(exchange.mutate().request(decorator).build())
})
}
private fun decorate(
exchange: ServerWebExchange,
headers: HttpHeaders,
outputMessage: CachedBodyOutputMessage
): ServerHttpRequestDecorator {
return object : ServerHttpRequestDecorator(exchange.request) {
override fun getHeaders(): HttpHeaders {
val contentLength = headers.contentLength
val httpHeaders = HttpHeaders()
httpHeaders.putAll(super.getHeaders())
if (contentLength > 0) {
httpHeaders.contentLength = contentLength
} else {
// TODO: this causes a 'HTTP/1.1 411 Length Required' // on
// httpbin.org
httpHeaders.set(HttpHeaders.TRANSFER_ENCODING, "chunked")
}
return httpHeaders
}
override fun getBody(): Flux<DataBuffer> {
return outputMessage.body
}
}
}
}

然后BodyFilter的实现要么在失败时返回Mono.empty()，要么在成功时调用passRequestFunction。