一文教你如何使用原生的Feign

    <properties>
        <feign.version>11.2</feign.version>
    </properties>
    
    <dependencies>
        <dependency>
            <groupId>io.GitHub.openfeign</groupId>
            <artifactId>feign-core</artifactId>
            <version>${feign.version}</version>
        </dependency>
        <dependency>
            <groupId>io.github.openfeign</groupId>
            <artifactId>feign-gson</artifactId>
            <version>${feign.version}</version>
        </dependency>
    </dependencies>

// 定义HTTP API
interface GitHub {
    
    @RequestLine("GET /repos/{owner}/{repo}/contributors")
    // @RequestLine(value = "GET /repos/{owner}/{repo}/contributors", decodeSlash = false)// 测试转义"/"、"+"
    // @RequestLine("GET /repos/{owner:[a-zA-Z]*}/{repo}/contributors")// 测试正则校验
    // @Headers("Accept: application/json") // 测试添加header
    List<Contributor> contributors(@Param("owner") String owner, @Param("repo") String repo);
}

public static class Contributor {
    String login;
    int contributions;
}

public class MyApp {

    public static void main(String... args) {
        // 获取用来访问HTTP API的代理类
        GitHub github = Feign.builder()
                .decoder(new GsonDecoder()) // 返回内容为json格式，所以需要用到json解码器
                // .options(new Request.Options(10, TimeUnit.SECONDS, 60, TimeUnit.SECONDS, true)) // 配置超时参数等
                .target(GitHub.class, "https://api.github.com");

        // 像调用方法一样访问HTTP API
        github.contributors("OpenFeign", "feign").stream()
            .map(contributor -> contributor.login + " (" + contributor.contributions + ")")
            .forEach(System.out::println);
    }
}

// 定义HTTP API
interface GitHub {
    
    @GetMapping("/repos/{owner}/{repo}/contributors")
    List<Contributor> contributors(@RequestParam("owner") String owner, @RequestParam("repo") String repo);
}


public class MyApp {

    public static void main(String... args) {
        // 获取用来访问HTTP API的代理类
        GitHub github = Feign.builder()
                .decoder(new GsonDecoder())
                .contract(new SprinGContract())// 自定义contract
                .target(GitHub.class, "https://api.github.com");
    }
}

public class MyApp {

    public static void main(String... args) {
        // 获取用来访问HTTP API的代理类
        GitHub github = Feign.builder()
                .decoder(new JacksonDecoder()) // 自定义解码器
                .encoder(new JacksonEncoder()) // 自定义编码器
                .target(GitHub.class, "https://api.github.com");
    }
}

public class MyApp {

    public static void main(String... args) {
        // 获取用来访问HTTP API的代理类
        GitHub github = Feign.builder()
                .decoder(new GsonDecoder())
                .client(new OkHttpClient())// 自定义client
                .target(GitHub.class, "https://api.github.com");
    }
}

public class MyInterceptor implements RequestInterceptor {

    @Override
    public void apply(RequestTemplate template) {
        template.header("token", LoginUtils.getCurrentToken());
    }
}
public class MyApp {

    public static void main(String... args) {
        // 获取用来访问HTTP API的代理类
        GitHub github = Feign.builder()
                .decoder(new GsonDecoder())
                .requestInterceptor(new MyInterceptor())
                .target(GitHub.class, "https://api.github.com");
    }
}

public class MyRetryer implements Retryer {
    
    int attempt = 0;

    @Override
    public void continueOrPropagate(RetryableException e) {
        // 如果把RetryableException抛出，则不会继续重试
        // 否则继续重试
        if(attempt++ >= 3) {// 重试三次
            throw e;
        }
    }

    @Override
    public Retryer clone() {
        return this;
    }
}
public class MyApp {

    public static void main(String... args) {
        // 获取用来访问HTTP API的代理类
        GitHub github = Feign.builder()
                .decoder(new GsonDecoder())
                .retryer(new MyRetryer())
                //.retryer(Retryer.NEVER_RETRY) // 不重试
                .exceptionPropagationPolicy(ExceptionPropagationPolicy.UNWRAP)
                .target(GitHub.class, "https://api.github.com");
    }
}