如何自定义SpringWebFlux WebClient JSON反序列化？

Question

我正在使用spring-webflux WebClient (build 20170502.221452-172)来访问一个Web应用程序,生成一个Entry对象流(application/stream + json),如下所示:

final WebClient producerClient = WebClient.create("http://localhost:8080/");

Flux<Entry> entries = producerClient.get().uri("json-stream")
        .accept(MediaType.APPLICATION_STREAM_JSON)
        .exchange()
        .flatMapMany(clientResponse -> clientResponse.bodyToFlux(Entry.class));

虽然Entry对象的反序列化适用于使用标准公共类型的POJO,包括Java时间(JSR-310)数据类型,如java.time.Instant,但我想知道为了将任何自定义JSON添加到Java反序列化,我必须做什么(例如,自定义Jackson ObjectMapper).

我无法在WebClient或其构建器和流畅API生成的对象的类中找到任何API 来执行此操作.

有没有人使用WebClient进行自定义反序列化？

(也许API不存在,但是？)

Answer 1

这是一个自定义ObjectMapperfor JSON(de)序列化的示例.请注意,出于流式传输的目的,正在使用不同的编码器/解码器,但其配置原则保持不变.

    ExchangeStrategies strategies = ExchangeStrategies
            .builder()
            .codecs(clientDefaultCodecsConfigurer -> {
                clientDefaultCodecsConfigurer.defaultCodecs().jackson2JsonEncoder(new Jackson2JsonEncoder(new ObjectMapper(), MediaType.APPLICATION_JSON));
                clientDefaultCodecsConfigurer.defaultCodecs().jackson2JsonDecoder(new Jackson2JsonDecoder(new ObjectMapper(), MediaType.APPLICATION_JSON));

            }).build();

    WebClient webClient = WebClient.builder().exchangeStrategies(strategies).build();

Answer 2

根据上面的回复，我最终得到了这段代码：

final ObjectMapper mapper = new ObjectMapper()
    .findAndRegisterModules()
    .enable(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT);
final ExchangeStrategies exchangeStrategies = ExchangeStrategies.builder()
    .codecs(configurer -> configurer.defaultCodecs()
    .jackson2JsonDecoder(new Jackson2JsonDecoder(mapper)))
    .build();
final WebClient webClient = WebClient.builder()
    .exchangeStrategies(exchangeStrategies)
    .build();

如果不包含.findAndRegisterModules()，当您想要反序列化 Java 8 的时间对象等内容时，就会遇到问题。

Answer 3

您可以为特定的 WebClient 配置它：

@Autowired
public ItunesAlbumServiceImpl(ObjectMapper mapper) {
    ExchangeStrategies strategies = ExchangeStrategies.builder().codecs(clientCodecConfigurer ->
        clientCodecConfigurer.customCodecs().decoder(
                new Jackson2JsonDecoder(mapper,
                        new MimeType("text", "javascript", StandardCharsets.UTF_8)))
    ).build();

    webClient = WebClient.builder()
            .exchangeStrategies(strategies)
            .baseUrl("https://itunes.apple.com")
            .build();
}

但也在“应用程序级别”

通过配置一个CodecCustomizer：

@Bean
public CodecCustomizer jacksonLegacyJsonCustomizer(ObjectMapper mapper) {
    return (configurer) -> {
        MimeType textJavascript = new MimeType("text", "javascript", StandardCharsets.UTF_8);
        CodecConfigurer.CustomCodecs customCodecs = configurer.customCodecs();
        customCodecs.decoder(
                new Jackson2JsonDecoder(mapper, textJavascript));
        customCodecs.encoder(
                new Jackson2JsonEncoder(mapper, textJavascript));
    };
}

这将通过WebClientAutoConfiguration作为WebClient.Builderbean 来实现：

@Autowired
public ItunesAlbumServiceImpl(WebClient.Builder webclientBuilder) {
    webClient = webclientBuilder.baseUrl("https://itunes.apple.com").build();
}

Answer 4

全局配置：

@Configuration
public class AppConfig {

    private final ObjectMapper objectMapper;

    @Autowired
    public AppConfig(ObjectMapper objectMapper) {
        this.objectMapper = objectMapper;
        this.webClientBuilder = WebClient.builder()
                .exchangeStrategies(exchangeStrategies());
    }

    private ExchangeStrategies exchangeStrategies() {
        Jackson2JsonEncoder encoder = new Jackson2JsonEncoder(objectMapper);
        Jackson2JsonDecoder decoder = new Jackson2JsonDecoder(objectMapper);
        return ExchangeStrategies
                .builder()
                .codecs(configurer -> {
                    configurer.defaultCodecs().jackson2JsonEncoder(encoder);
                    configurer.defaultCodecs().jackson2JsonDecoder(decoder);
                }).build();
    }
}

Answer 5

从 Spring 开始，5.1.13您可以使用专用.codec方法来自定义它们：

WebClient.builder()
    .codecs(configurer -> {
        configurer.defaultCodecs().jackson2JsonEncoder(new Jackson2JsonEncoder(new ObjectMapper(), MediaType.APPLICATION_JSON));
        configurer.defaultCodecs().jackson2JsonDecoder(new Jackson2JsonDecoder(new ObjectMapper(), MediaType.APPLICATION_JSON));
     })
    .build();

Answer 6

使用 webflux 5.0.2，取消注册默认值

val strategies = ExchangeStrategies.builder()
                .codecs { configurer ->
                    configurer.registerDefaults(false)
                    configurer.customCodecs().encoder(Jackson2JsonEncoder(objectMapper, APPLICATION_JSON))
                    configurer.customCodecs().decoder(Jackson2JsonDecoder(objectMapper, APPLICATION_JSON))
                }.build()