Feign Client使用@PatchMapping或PATCH方法报错：无效HTTP方法

java.net.ProtocolException: 无效的HTTP方法: PATCH
at java.base/java.net.HttpURLConnection.setRequestMethod(HttpURLConnection.java:489)
at java.base/sun.net.www.protocol.http.HttpURLConnection.setRequestMethod(HttpURLConnection.java:598)
at feign.Client$Default.convertAndSend(Client.java:171)
at feign.Client$Default.execute(Client.java:105)
at org.springframework.cloud.openfeign.loadbalancer.LoadBalancerUtils.executeWithLoadBalancerLifecycleProcessing(LoadBalancerUtils.java:56)
at org.springframework.cloud.openfeign.loadbalancer.RetryableFeignBlockingLoadBalancerClient.lambda$execute$2(RetryableFeignBlockingLoadBalancerClient.java:189)
at org.springframework.retry.support.RetryTemplate.doExecute(RetryTemplate.java:329)
at org.springframework.retry.support.RetryTemplate.execute(RetryTemplate.java:225)
at org.springframework.cloud.openfeign.loadbalancer.RetryableFeignBlockingLoadBalancerClient.execute(RetryableFeignBlockingLoadBalancerClient.java:136)
at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:100)
... 183 more

问题原因 #

JDK原生的HttpURLConnection默认不支持PATCH HTTP方法，而Feign默认使用该客户端发送请求，因此调用PATCH接口时会触发此异常。

解决方案 #

方案1：切换Feign的HTTP客户端为OkHttp #

步骤1：引入OkHttp依赖（Maven）

<dependency>
    <groupId>io.github.openfeign</groupId>
    <artifactId>feign-okhttp</artifactId>
</dependency>
<dependency>
    <groupId>com.squareup.okhttp3</groupId>
    <artifactId>okhttp</artifactId>
</dependency>

步骤2：配置Feign启用OkHttp

在application.yml中添加配置：

feign:
  okhttp:
    enabled: true

方案2：切换为Apache HttpClient #

步骤1：引入Apache HttpClient依赖（Maven）

<dependency>
    <groupId>io.github.openfeign</groupId>
    <artifactId>feign-httpclient</artifactId>
</dependency>

步骤2：配置Feign启用Apache HttpClient

在application.yml中添加配置：

feign:
  httpclient:
    enabled: true

方案3：自定义Feign Client兼容PATCH方法（不换客户端） #

如果不想更换HTTP客户端，可以通过自定义Feign Client，利用反射绕过HttpURLConnection的方法限制：

import feign.Client;
import feign.Request;
import feign.Response;
import java.io.IOException;
import java.lang.reflect.Field;
import java.net.HttpURLConnection;
import java.net.ProtocolException;

public class PatchCompatibleFeignClient extends Client.Default {

    public PatchCompatibleFeignClient() {
        super(null, null);
    }

    @Override
    public Response execute(Request request, Request.Options options) throws IOException {
        if (request.method().equals("PATCH")) {
            return executePatchRequest(request, options);
        }
        return super.execute(request, options);
    }

    private Response executePatchRequest(Request request, Request.Options options) throws IOException {
        HttpURLConnection connection = (HttpURLConnection) request.url().openConnection();
        configureConnection(connection, options);

        try {
            // 反射修改method字段，绕过HttpURLConnection的方法限制
            Field methodField = HttpURLConnection.class.getDeclaredField("method");
            methodField.setAccessible(true);
            methodField.set(connection, "PATCH");
        } catch (NoSuchFieldException | IllegalAccessException e) {
            throw new ProtocolException("Failed to set PATCH method", e);
        }

        if (request.body() != null) {
            connection.setDoOutput(true);
            connection.addRequestHeader(request.headers().get("Content-Type").iterator().next(), request.body().toString());
            request.body().writeTo(connection.getOutputStream());
        }

        return super.convertResponse(connection, request);
    }
}

然后在配置类中注册这个自定义Client：

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class FeignConfig {
    @Bean
    public Client feignClient() {
        return new PatchCompatibleFeignClient();
    }
}

内容的提问来源于stack exchange，提问作者Santhoshkannan