javax.json.JsonPatch 在 Spring Webflux 微服务中不支持 @RequestBody

Question

我目前正在摆弄一个 Spring Webflux 微服务，并尝试实现一个 @PatchMapping，它使用一个 JsonPatch 对象作为 @RequestBody，如下所示：

@PatchMapping("/{id}", consumes = ["application/json-patch+json"])
fun updateFriend( @PathVariable("id") id: Long, 
                  @Valid @RequestBody jsonPatch: JsonPatch): Mono<UserFriends> {
    // apply JsonPatch code here...
}

我使用 Postman 请求测试了端点，如下所示：

PATCH <microservice-uri>/friends/1
Content-Type = application/json-patch+json
RequestBody = 
[
    {
        "op": "replace",
        "path": "friends/11/since",
        "value": "<sample value>"
    }
]

这是我遇到的异常：

org.springframework.core.codec.CodecException: Type definition error: [simple type, class javax.json.JsonPatch]; nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `javax.json.JsonPatch` (no Creators, like default construct, exist): abstract types either need to be mapped to concrete types, have custom deserializer, or contain additional type information
 at [Source: (io.netty.buffer.ByteBufInputStream); line: 1, column: 1]
    at org.springframework.http.codec.json.AbstractJackson2Decoder.processException(AbstractJackson2Decoder.java:211) ~[spring-web-5.2.6.RELEASE.jar:5.2.6.RELEASE]
    Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: 
Error has been observed at the following site(s):
    |_ checkpoint ⇢ HTTP PATCH "/friends/1" [ExceptionHandlingWebHandler]
<Additional stacktraces here ...>

我很清楚，我需要告诉我的微服务如何将 RequestBody 转换为 JsonPatch。但在失败了 3 天后，我决定寻求帮助。

在多次尝试失败后，我找到了 WebFluxConfigurer 并尝试覆盖 configureArgumentResolvers。我在为 JsonPatch 编写 HandlerMethodArgumentResolver 时卡住了。

class JsonPatchResolver : HandlerMethodArgumentResolver {
    override fun supportsParameter(parameter: MethodParameter): Boolean {
        // Don't know what to implement here
    }

    override fun resolveArgument(parameter: MethodParameter, bindingContext: BindingContext, exchange: ServerWebExchange): Mono<Any> {
        // Don't know how to create a JsonPatch from the given arguments
    }
}

有人可以指出我正确的方向或告诉我我做错了什么吗？

非常感谢您！

编辑这是我的 pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.7.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>friend-info-service</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>friend-info-service</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>11</java.version>
        <kotlin.version>1.3.72</kotlin.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-webflux</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-mongodb-reactive</artifactId>
        </dependency>
        <dependency>
            <groupId>de.flapdoodle.embed</groupId>
            <artifactId>de.flapdoodle.embed.mongo</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>com.github.java-json-tools</groupId>
            <artifactId>json-patch</artifactId>
            <version>1.12</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.module</groupId>
            <artifactId>jackson-module-kotlin</artifactId>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.datatype</groupId>
            <artifactId>jackson-datatype-jsr353</artifactId>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-reflect</artifactId>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-stdlib-jdk8</artifactId>
        </dependency>
        <dependency>
            <groupId>javax.json</groupId>
            <artifactId>javax.json-api</artifactId>
        </dependency>

        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-engine</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-api</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.mockito</groupId>
            <artifactId>mockito-junit-jupiter</artifactId>
            <scope>test</scope>
        </dependency>

    </dependencies>

    <build>
        <sourceDirectory>${project.basedir}/src/main/kotlin</sourceDirectory>
        <testSourceDirectory>${project.basedir}/src/test/kotlin</testSourceDirectory>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>org.jetbrains.kotlin</groupId>
                <artifactId>kotlin-maven-plugin</artifactId>
                <configuration>
                    <args>
                        <arg>-Xjsr305=strict</arg>
                    </args>
                    <compilerPlugins>
                        <plugin>spring</plugin>
                    </compilerPlugins>
                </configuration>
                <dependencies>
                    <dependency>
                        <groupId>org.jetbrains.kotlin</groupId>
                        <artifactId>kotlin-maven-allopen</artifactId>
                        <version>${kotlin.version}</version>
                    </dependency>
                </dependencies>
            </plugin>
        </plugins>
    </build>

</project>

编辑 2 以下不起作用：

class JsonPatchArgumentResolver : HandlerMethodArgumentResolver {

    override fun supportsParameter(parameter: MethodParameter): Boolean {
        // this doesn't event get called when debugging, so I suspect the handler isn't registered correctly
        return parameter.parameterType == JsonPatch::class
    }

    override fun resolveArgument(parameter: MethodParameter, bindingContext: BindingContext, exchange: ServerWebExchange): Mono<Any> {
        return exchange.request.body.toMono().map {
            jacksonObjectMapper().readValue(it.asInputStream(), JsonPatch::class.java)
        }
    }

}

在我的申请中 class 我正在注册它（可能是错误的，我不知道）：

@SpringBootApplication
@EnableReactiveMongoRepositories
@EnableWebFlux
@Configuration
class FriendInfoServiceApplication : WebFluxConfigurer {
    override fun configureArgumentResolvers(configurer: ArgumentResolverConfigurer) {
        configurer.addCustomResolver(JsonPatchArgumentResolver())
    }
}

fun main(args: Array<String>) {
    runApplication<FriendInfoServiceApplication>(*args)
}

编辑 3 在调试时我发现 configureArgumentResolvers get 被调用了，所以也许我对 supportsParameter?

做错了什么

编辑 4 我尝试从 THIS 博客 post 复制代码。科特林等价物应该是：


@Component
class JsonPatchHttpMessageConverter : AbstractHttpMessageConverter<JsonPatch>() {

    @Throws(HttpMessageNotReadableException::class)
    protected override fun readInternal(clazz: Class<out JsonPatch>, inputMessage: HttpInputMessage): JsonPatch {
        try {
            Json.createReader(inputMessage.body).use { reader -> return Json.createPatch(reader.readArray()) }
        } catch (e: Exception) {
            throw HttpMessageNotReadableException(e.message!!, inputMessage)
        }
    }

    @Throws(HttpMessageNotWritableException::class)
    protected override fun writeInternal(jsonPatch: JsonPatch, outputMessage: HttpOutputMessage) {
        throw NotImplementedError("The write Json patch is not implemented")
    }


    protected override fun supports(clazz: Class<*>): Boolean {
        return JsonPatch::class.java.isAssignableFrom(clazz)
    }
}

并将 objectMapper 添加到应用程序 class 中，如下所示：

@SpringBootApplication
@EnableReactiveMongoRepositories
@EnableWebFlux
@Configuration
class FriendInfoServiceApplication {
    @Bean
    fun objectMapper(): ObjectMapper {
        val objectMapper = ObjectMapper()
        objectMapper.registerModule(JSR353Module())
        return objectMapper
    }
}

不幸的是，当尝试调用 PATCH 端点时，结果是相同的异常。

Answer 1

我是您提到的博客 post 的作者。我不是 Webflux 方面的专家，但在这种情况下，您必须将 JacksonConverter 重新实现为 webFlux 表单。

于是变成了这样：

import org.springframework.core.ResolvableType
import org.springframework.core.io.buffer.DataBuffer
import org.springframework.core.io.buffer.DataBufferUtils
import org.springframework.http.MediaType
import org.springframework.http.ReactiveHttpInputMessage
import org.springframework.http.codec.HttpMessageReader
import reactor.core.publisher.Flux
import reactor.core.publisher.Mono
import javax.json.Json
import javax.json.JsonPatch

class JsonPatchHttpMessageConverter : HttpMessageReader<JsonPatch> {
    override fun getReadableMediaTypes(): List<MediaType> {
        return listOf(MediaType.valueOf("application/json-patch+json"))
    }

    override fun canRead(elementType: ResolvableType, mediaType: MediaType?): Boolean {
        return MediaType.valueOf("application/json-patch+json").includes(mediaType)
    }

    override fun read(elementType: ResolvableType, message: ReactiveHttpInputMessage, hints: Map<String, Any>): Flux<JsonPatch> {
        //TODO implement the same mono logic here
        return Flux.empty();
    }

    override fun readMono(elementType: ResolvableType, message: ReactiveHttpInputMessage, hints: Map<String, Any>): Mono<JsonPatch> {
        return DataBufferUtils.join(message.body).map { buffer: DataBuffer ->
            //TODO error handling
            val reader = Json.createReader(buffer.asInputStream())
            Json.createPatch(reader.readArray())
        }
    }
}

请注意，它尚未完全实现，您必须进行错误处理并实现 read(elementType: ResolvableType, message: ReactiveHttpInputMessage, hints: Map<String, Any>): Flux<JsonPatch>。

现在您必须注册这个自定义解码器。在 spring webFlux 中，您可以通过创建 WebFluxConfigurer bean 来实现：

@Bean
fun webFluxConfigurer(): WebFluxConfigurer {
    return object : WebFluxConfigurer {
        override fun configureHttpMessageCodecs(configurer: ServerCodecConfigurer) {
            configurer.customCodecs().register(JsonPatchHttpMessageConverter())
        }
    }
}

最后是路由器和处理程序：

@Configuration
class GreetingRouter {
    @Bean
    fun route(greetingHandler: GreetingHandler): RouterFunction<ServerResponse> {
        return RouterFunctions
                .route(RequestPredicates.POST("/hello")
                        .and(RequestPredicates.accept(MediaType.valueOf("application/json-patch+json"))), HandlerFunction { request: ServerRequest? -> greetingHandler.hello(request!!) })
    }

}


@Component
class GreetingHandler {
    fun hello(request: ServerRequest): Mono<ServerResponse> {
        return request.bodyToMono(JsonPatch::class.java)
                .flatMap { jsonPatch: JsonPatch ->
                    ServerResponse.ok().contentType(MediaType.valueOf("application/json-patch+json"))
                            .body(BodyInserters.fromValue("Received: $jsonPatch"))
                }
    }
}

最后，您可以使用 curl 调用此端点，例如：

curl -X POST \
  http://localhost:8080/hello \
  -H 'content-type: application/json-patch+json' \
  -d '[
   {
      "op":"replace",
      "path":"/email",
      "value":"email@email.com"
   }
]'

javax.json.JsonPatch 在 Spring Webflux 微服务中不支持 @RequestBody

javax.json.JsonPatch unsupported as @RequestBody in Spring Webflux Microservice

spring-boot

kotlin

spring-webflux

json-patch