Http客户端--Feign简介

1 Feign简介

• Feign是一个声明式的http客户端，作用就是帮助我们优雅的实现http请求的发送，解决RestTemplate的问题。

1.1 RestTemplate发送get请求

		RestTemplateBuilder builder = new RestTemplateBuilder();
        RestTemplate restTemplate = builder.build();
		String url = "https://v2.alapi.cn/api/new/wbtop?num=100&token=4DZmP3cZ930V2z7X";
        String forObject = restTemplate.getForObject(url, String.class);
        JSONObject jsonObject = JSONObject.parseObject(forObject);
        Object data = jsonObject.get("data");
        List<WeiBoHotVO> dataJson = JSONObject.parseArray(data.toString(), WeiBoHotVO.class);
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1.2 RestTemplate发送post请求

• 发送参数

		String url = "*****";
        MultiValueMap map = new LinkedMultiValueMap();
        map.add("username", username);
        map.add("password", password);
        ResponseEntity<String> responseEntity = restTemplate.postForEntity(url, map, String.class);
        return responseEntity.getBody();
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• 发送json

		String url = "*****";
        Member member = new Member();
        member.setEmail(username);
        member.setPassword(password);
        ResponseEntity<Member> memberResponseEntity = restTemplate.postForEntity(url, member, Member.class);
        return memberResponseEntity.getBody();
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1.3 RestTemplate发送通用请求

String url = "*****";
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON_UTF8);
        //设置访问参数
        HashMap<String, Object> params = new HashMap<>();
        params.put("username", username);
        //设置访问的Entity
        HttpEntity entity = new HttpEntity<>(params, headers);
        ResponseEntity<String> result;
        try {
            //发起一个POST请求
            result = restTemplate.exchange(url, HttpMethod.POST, entity, String.class);
            JSONObject data = JSONObject.parseObject(result.getBody()).getJSONObject("data");
            return data.getString("id");
        } catch (Exception e) {
        }
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2 Feign客户端的使用

2.1 引入依赖

        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-openfeignartifactId>
        dependency>
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2.2 第二步添加注解@EnableFeignClients

@EnableFeignClients
public @interface EnableMyFeignClients{
}
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2.3 编写Feign客户端

声明：服务名称、请求方式、请求路径、请求参数、返回值类型

@FeignClient("userservice")
public interface UserClient{
	@GetMapping("/user/{id}")
	User findById(@PathVariable("id" Long id));
}
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3 Feign的自定义配置

• 日志级别NONE、BASIC、HEADERS、FULL
• 方式一：配置文件

feign:
	client:
		config:
			default: #全局配置可以指定服务名称
				loggerLevel: BASIC
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• 方式二： java代码
• 自定义日志

@Component
public class RemoteUserFallbackFactory implements FallbackFactory<RemoteUserService>
{
    private static final Logger log = LoggerFactory.getLogger(RemoteUserFallbackFactory.class);

    @Override
    public RemoteUserService create(Throwable throwable)
    {
        log.error("用户服务调用失败:{}", throwable.getMessage());
        return new RemoteUserService()
        {
            @Override
            public R<LoginUser> getUserInfo(String username, String source)
            {
                return R.fail("获取用户失败:" + throwable.getMessage());
            }

            @Override
            public R<Boolean> registerUserInfo(SysUser sysUser, String source)
            {
                return R.fail("注册用户失败:" + throwable.getMessage());
            }
        };
    }
}
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• 使用自定义日志

@FeignClient(contextId = "remoteUserService", value = ServiceNameConstants.SYSTEM_SERVICE, fallbackFactory = RemoteUserFallbackFactory.class)
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4 Feign的性能优化

Feign底层的客户端实现：

• URLConnection：默认实现，不支持连接池
• Apache HttpClient：支持连接池
• OKHttp：支持连接池
  性能优化主要包括：
• 使用连接池代替默认的URLConnection

# feign 配置
feign:
  sentinel:
    enabled: true
  okhttp:
    enabled: true
  httpclient:
    enabled: false
  client:
    config:
      default:
        connectTimeout: 10000
        readTimeout: 10000
  compression:
    request:
      enabled: true
    response:
      enabled: true
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• 日志级别，最好用basic或none