如何从Spring WebClient的ClientResponse中获取最佳字节数组？ [英] How to best get a byte array from a ClientResponse from Spring WebClient?

问题描述

我在Spring 5（5.0.0.RC2）中尝试使用反应式编程的代码库中的新 WebClient ，并且我已经成功映射了JSON从我的应用程序中的端点到DTO的响应非常好：

I'm trying out the new WebClient from Spring 5 (5.0.0.RC2) in a codebase that uses reactive programming and I've had success mapping the JSON response from an endpoint to a DTO in my app, which works very nice:

WebClient client = WebClient.create(baseURI);
Mono<DTO> dto = client.get()
        .uri(uri)
        .accept(MediaType.APPLICATION_JSON)
        .exchange()
        .flatMap(response -> response.bodyToMono(DTO.class));

但是，现在我正在尝试使用协议缓冲区（二进制数据）的端点的响应主体作为 application / octet-stream ），所以我想从响应中获取原始字节，然后我将自己映射到一个对象。

However, now I'm trying to the response body from an endpoint which uses Protocol Buffers (binary data served as application/octet-stream), so I'd like to get the raw bytes from the response, which I'll then map to an object myself.

我使用来自Google Guava的 Bytes 这样工作：

I got it to work like this using Bytes from Google Guava:

Mono<byte[]> bytes = client.get()
        .uri(uri)
        .accept(MediaType.APPLICATION_OCTET_STREAM)
        .exchange()
        .flatMapMany(response -> response.body(BodyExtractors.toDataBuffers()))
        .map(dataBuffer -> {
            ByteBuffer byteBuffer = dataBuffer.asByteBuffer();
            byte[] byteArray = new byte[byteBuffer.remaining()];
            byteBuffer.get(byteArray, 0, bytes.length);
            return byteArray;
        })
        .reduce(Bytes::concat)

这有效，但是有更简单，更优雅的方法来获取这些字节吗？

This works, but is there an easier, more elegant way to get these bytes?

推荐答案

ClientResponse.bodyToMono（）最后使用了一些 org.springframework.core.codec声明支持指定类的.Decoder 。

所以我们应该检查解码器的类层次结构，特别是 decodeToMono（）的地点和方式方法已实现。

So we should check the class hierarchy of the Decoder, in particular where and how the decodeToMono() method is implemented.

有一个 StringDecoder 支持解码为 String ，一堆与Jackson相关的解码器（在你的DTO示例中使用），还有一个特别感兴趣的 ResourceDecoder 。

There is a StringDecoder which supports decoding to String, a bunch of Jackson-related decoders (used in your DTO example under the hood), and there is also a ResourceDecoder which is of particular interest.

ResourceDecoder 支持 org.springframework.core.io.InputStreamResource 和 org.springframework.core.io.ByteArrayResource 。 ByteArrayResource 本质上是 byte [] 的包装器，因此以下代码将提供对响应主体的访问，字节数组：

ResourceDecoder supports org.springframework.core.io.InputStreamResource and org.springframework.core.io.ByteArrayResource. ByteArrayResource is essentially a wrapper around byte[], so the following code will provide an access to the response body as a byte array:

Mono<byte[]> mono = client.get()
            ...
            .exchange()
            .flatMap(response -> response.bodyToMono(ByteArrayResource.class))
            .map(ByteArrayResource::getByteArray);

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