WebExceptionHandler:如何使用Spring Webflux编写正文

Question

我想通过添加WebExceptionHandler来处理我的api的异常.我可以更改状态代码,但是当我想要更改响应的主体时,我会陷入困境:ex添加异常消息或自定义对象.

有人有例吗？

我如何添加我的WebExceptionHandler:

HttpHandler httpHandler = WebHttpHandlerBuilder.webHandler(toHttpHandler(routerFunction))
  .prependExceptionHandler((serverWebExchange, exception) -> {

      exchange.getResponse().setStatusCode(myStatusGivenTheException);
      exchange.getResponse().writeAndFlushWith(??)
      return Mono.empty();

  }).build();

Answer 1

WebExceptionHandler 级别较低，因此您必须直接处理请求/响应交换。

注意：

• 该Mono<Void>返回类型应信号的响应处理结束; 这就是为什么它应该与Publisher编写响应相关联的原因
• 在此级别上，您正在直接处理数据缓冲区（不提供序列化支持）

您WebExceptionHandler可能看起来像这样：

(serverWebExchange, exception) -> {

  exchange.getResponse().setStatusCode(myStatusGivenTheException);
  byte[] bytes = "Some text".getBytes(StandardCharsets.UTF_8);
  DataBuffer buffer = exchange.getResponse().bufferFactory().wrap(bytes);
  return exchange.getResponse().writeWith(Flux.just(buffer));
}

Answer 2

给出答案，要序列化对象，我使用这种方式：

 Mono<DataBuffer> db = commonsException.getErrorsResponse().map(errorsResponse -> {

     ObjectMapper objectMapper = new ObjectMapper();
     try {
         return objectMapper.writeValueAsBytes(errorsResponse);
     } catch (JsonProcessingException e) {
          return e.getMessage().getBytes();
     }
}).map(s -> exchange.getResponse().bufferFactory().wrap(s));

exchange.getResponse().getHeaders().add("Content-Type", "application/json");
exchange.getResponse().setStatusCode(commonsException.getHttpStatus());
return exchange.getResponse().writeWith(db);

Answer 3

ServerResponse有一个方法writeTo可以用来写入你的body ServerExchange（Spring框架就是这样做的）。唯一的问题是您必须提供Context第二个参数，所以我刚刚HandlerStrategiesResponseContext从框架实现中复制了。

确保您至少使用 Spring Boot 2.0.0 M2，在WebExceptionHandler使用RouterFunctions.

import org.springframework.http.HttpStatus
import org.springframework.http.HttpStatus.*
import org.springframework.http.codec.HttpMessageWriter
import org.springframework.stereotype.Component
import org.springframework.web.reactive.function.server.HandlerStrategies
import org.springframework.web.reactive.function.server.ServerResponse
import org.springframework.web.reactive.result.view.ViewResolver
import org.springframework.web.server.ServerWebExchange
import org.springframework.web.server.WebExceptionHandler


@Component
class GlobalErrorHandler() : WebExceptionHandler {

    override fun handle(exchange: ServerWebExchange, ex: Throwable): Mono<Void> =
        handle(ex)
                .flatMap {
                    it.writeTo(exchange, HandlerStrategiesResponseContext(HandlerStrategies.withDefaults()))
                }
                .flatMap {
                    Mono.empty<Void>()
                }

    fun handle(throwable: Throwable): Mono<ServerResponse> {

        return when (throwable) {
            is EntityNotFoundException -> {
                createResponse(NOT_FOUND, "NOT_FOUND", "Entity not found, details: ${throwable.message}")
            }
            else -> {
                createResponse(INTERNAL_SERVER_ERROR, "GENERIC_ERROR", "Unhandled exception")
            }
        }
    }

    fun createResponse(httpStatus: HttpStatus, code: String, message: String): Mono<ServerResponse> =
        ServerResponse.status(httpStatus).syncBody(ApiError(code, message))
}

private class HandlerStrategiesResponseContext(val strategies: HandlerStrategies) : ServerResponse.Context {

    override fun messageWriters(): List<HttpMessageWriter<*>> {
        return this.strategies.messageWriters()
    }

    override fun viewResolvers(): List<ViewResolver> {
        return this.strategies.viewResolvers()
    }
}