使用Spring WebFlux的WebClient处理HTTP 400状态码的详细指南

在Java中，使用WebClient（通常是Spring WebFlux提供的非阻塞客户端）进行HTTP请求时，可能会遇到各种HTTP状态码，包括400状态码（Bad Request）。处理400状态码通常意味着服务器无法理解请求，可能是因为请求的格式不正确或包含无效参数。

以下是如何使用WebClient解析和处理400状态码的详细步骤：

1. 引入依赖

确保你的项目中已经包含了Spring WebFlux的依赖。如果你使用的是Maven，可以在pom.xml中添加以下依赖：


<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-webflux</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-webflux</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-webflux</artifactId>
</dependency>

2. 创建WebClient实例

你可以通过WebClient.Builder来创建一个WebClient实例：


import org.springframework.web.reactive.function.client.WebClient;
public class MyWebClient {
    private final WebClient webClient;
    public MyWebClient() {
        this.webClient = WebClient.builder()
                .baseUrl("http://example.com") // 替换为你的基础URL
                .build();
    }
}
import org.springframework.web.reactive.function.client.WebClient;

public class MyWebClient {
    private final WebClient webClient;

    public MyWebClient() {
        this.webClient = WebClient.builder()
                .baseUrl("http://example.com") // 替换为你的基础URL
                .build();
    }
}
import org.springframework.web.reactive.function.client.WebClient;

public class MyWebClient {
    private final WebClient webClient;

    public MyWebClient() {
        this.webClient = WebClient.builder()
                .baseUrl("http://example.com") // 替换为你的基础URL
                .build();
    }
}

3. 发送请求并处理400状态码

当你发送请求时，可以使用onStatus方法来检查特定的HTTP状态码，并处理它们。对于400状态码，你可以使用doOnError或onStatus中的lambda表达式来捕获错误并处理。

下面是一个完整的示例，展示如何发送一个POST请求并处理400状态码：


import org.springframework.http.HttpStatus;
import org.springframework.web.reactive.function.BodyInserters;
import org.springframework.web.reactive.function.client.ClientResponse;
import org.springframework.web.reactive.function.client.WebClient;
import org.springframework.web.reactive.function.client.WebClient.RequestBodyUriSpec;
import org.springframework.web.reactive.function.client.WebClient.RequestHeadersSpec;
import org.springframework.web.reactive.function.client.WebClient.ResponseSpec;
import reactor.core.publisher.Mono;
import java.util.HashMap;
import java.util.Map;
public class MyWebClient {
    private final WebClient webClient;
    public MyWebClient() {
        this.webClient = WebClient.builder()
                .baseUrl("http://example.com") // 替换为你的基础URL
                .build();
    }
    public Mono<String> sendPostRequest(Map<String, String> requestPayload) {
        return webClient.post()
                .uri("/your-endpoint") // 替换为你的实际端点
                .body(BodyInserters.fromValue(requestPayload))
                .retrieve()
                .onStatus(status -> status.value() == HttpStatus.BAD_REQUEST.value(),
                        clientResponse -> Mono.error(new RuntimeException("Received 400 Bad Request: " + clientResponse.statusCode())))
                .onStatus(status -> status.is4xxClientError(),
                        clientResponse -> Mono.error(new RuntimeException("Client error: " + clientResponse.statusCode())))
                .bodyToMono(String.class);
    }
    public static void main(String[] args) {
        MyWebClient myWebClient = new MyWebClient();
        Map<String, String> requestPayload = new HashMap<>();
        requestPayload.put("key1", "value1");
        requestPayload.put("key2", "invalid_value"); // 假设这个值会导致400错误
        myWebClient.sendPostRequest(requestPayload)
                .doOnError(error -> System.err.println("Error: " + error.getMessage()))
                .block(); // 注意：block()仅用于演示，在生产代码中应避免使用
    }
}
import org.springframework.http.HttpStatus;
import org.springframework.web.reactive.function.BodyInserters;
import org.springframework.web.reactive.function.client.ClientResponse;
import org.springframework.web.reactive.function.client.WebClient;
import org.springframework.web.reactive.function.client.WebClient.RequestBodyUriSpec;
import org.springframework.web.reactive.function.client.WebClient.RequestHeadersSpec;
import org.springframework.web.reactive.function.client.WebClient.ResponseSpec;
import reactor.core.publisher.Mono;

import java.util.HashMap;
import java.util.Map;

public class MyWebClient {
    private final WebClient webClient;

    public MyWebClient() {
        this.webClient = WebClient.builder()
                .baseUrl("http://example.com") // 替换为你的基础URL
                .build();
    }

    public Mono<String> sendPostRequest(Map<String, String> requestPayload) {
        return webClient.post()
                .uri("/your-endpoint") // 替换为你的实际端点
                .body(BodyInserters.fromValue(requestPayload))
                .retrieve()
                .onStatus(status -> status.value() == HttpStatus.BAD_REQUEST.value(),
                        clientResponse -> Mono.error(new RuntimeException("Received 400 Bad Request: " + clientResponse.statusCode())))
                .onStatus(status -> status.is4xxClientError(),
                        clientResponse -> Mono.error(new RuntimeException("Client error: " + clientResponse.statusCode())))
                .bodyToMono(String.class);
    }

    public static void main(String[] args) {
        MyWebClient myWebClient = new MyWebClient();

        Map<String, String> requestPayload = new HashMap<>();
        requestPayload.put("key1", "value1");
        requestPayload.put("key2", "invalid_value"); // 假设这个值会导致400错误

        myWebClient.sendPostRequest(requestPayload)
                .doOnError(error -> System.err.println("Error: " + error.getMessage()))
                .block(); // 注意：block()仅用于演示，在生产代码中应避免使用
    }
}
import org.springframework.http.HttpStatus;
import org.springframework.web.reactive.function.BodyInserters;
import org.springframework.web.reactive.function.client.ClientResponse;
import org.springframework.web.reactive.function.client.WebClient;
import org.springframework.web.reactive.function.client.WebClient.RequestBodyUriSpec;
import org.springframework.web.reactive.function.client.WebClient.RequestHeadersSpec;
import org.springframework.web.reactive.function.client.WebClient.ResponseSpec;
import reactor.core.publisher.Mono;

import java.util.HashMap;
import java.util.Map;

public class MyWebClient {
    private final WebClient webClient;

    public MyWebClient() {
        this.webClient = WebClient.builder()
                .baseUrl("http://example.com") // 替换为你的基础URL
                .build();
    }

    public Mono<String> sendPostRequest(Map<String, String> requestPayload) {
        return webClient.post()
                .uri("/your-endpoint") // 替换为你的实际端点
                .body(BodyInserters.fromValue(requestPayload))
                .retrieve()
                .onStatus(status -> status.value() == HttpStatus.BAD_REQUEST.value(),
                        clientResponse -> Mono.error(new RuntimeException("Received 400 Bad Request: " + clientResponse.statusCode())))
                .onStatus(status -> status.is4xxClientError(),
                        clientResponse -> Mono.error(new RuntimeException("Client error: " + clientResponse.statusCode())))
                .bodyToMono(String.class);
    }

    public static void main(String[] args) {
        MyWebClient myWebClient = new MyWebClient();

        Map<String, String> requestPayload = new HashMap<>();
        requestPayload.put("key1", "value1");
        requestPayload.put("key2", "invalid_value"); // 假设这个值会导致400错误

        myWebClient.sendPostRequest(requestPayload)
                .doOnError(error -> System.err.println("Error: " + error.getMessage()))
                .block(); // 注意：block()仅用于演示，在生产代码中应避免使用
    }
}

4. 解释代码

创建WebClient实例：使用WebClient.builder()来创建并配置一个WebClient实例。
发送请求：使用post()方法发送POST请求，并通过uri()设置请求的URI。
设置请求体：使用body(BodyInserters.fromValue(requestPayload))将请求体设置为一个Map。
处理状态码：
- 使用onStatus方法检查状态码是否为400（HttpStatus.BAD_REQUEST.value()）。
- 如果状态码是400，则返回一个包含错误信息的Mono.error。
- 还可以添加额外的onStatus来处理其他4xx客户端错误。
获取响应：使用bodyToMono(String.class)将响应体转换为Mono<String>。
处理错误：使用doOnError方法捕获并处理错误。