feign 调用https

要使用Feign调用HTTPS接口，需要在Feign的配置中启用HTTPS支持。具体步骤如下：

1. 引入Feign的依赖

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>

2. 配置Feign的HTTPS支持

@Configuration
public class FeignConfig {

    @Autowired
    private ObjectFactory<HttpMessageConverters> messageConverters;

    @Bean
    public Client feignClient() {
        return new Client.Default(getSSLSocketFactory(), null);
    }

    private SSLSocketFactory getSSLSocketFactory() {
        try {
            SSLContext sslContext = SSLContext.getInstance("TLS");
            sslContext.init(null, new TrustManager[] { new X509TrustManager() {
                public void checkClientTrusted(X509Certificate[] x509Certificates, String s) throws CertificateException {}
                public void checkServerTrusted(X509Certificate[] x509Certificates, String s) throws CertificateException {}
                public X509Certificate[] getAcceptedIssuers() { return new X509Certificate[0]; }
            } }, new SecureRandom());
            return sslContext.getSocketFactory();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    @Bean
    public Decoder feignDecoder() {
        return new ResponseEntityDecoder(new SpringDecoder(messageConverters));
    }
    
}

其中，`getSSLSocketFactory`方法返回一个`SSLSocketFactory`对象，用于创建HTTPS连接。这里采用了忽略证书的方式，实际生产环境中应该使用可信的证书。

3. 在Feign的接口中使用`https`协议

@FeignClient(name = "example", url = "https://example.com")
public interface ExampleClient {

    @GetMapping("/api")
    String get();
    
}

其中，`url`参数指定了HTTPS协议的地址。

这样就可以使用Feign调用HTTPS接口了。