在使用spring boot调用第三方api中，常用的是okhttp、apache http client等，但是直接使用下来还是有点繁琐，需要手动转换实体。
在springcloud中有个openfeign调用，第一次体验到调用接口还能这么丝滑。注解写道接口上，配置一下，其他交给框架处理。搜了一下这种方式叫做声明式调用。类似的还有Retrofit、forest框架。
openfeign集成到springboot中有何优点：openfeign吸收了Retrofit框架的优点，做了声明式API，但是没有Retrofit多余的Call层。forest是一款国产优秀的框架，单独使用问题不大，但对于后续升级到cloud的boot项目，共存时存在不少问题，并且对上传大文件部分场景的支持有点问题。
这里分两步，先介绍@RequestLine注解调用，后介绍@GetMapping的spring注解调用。
一、传统注解@RequestLine调用
1.加依赖
<!-- feign -->
<dependency>
<groupId>io.github.openfeign</groupId>
<artifactId>feign-core</artifactId>
<version>11.0</version>
</dependency>
<dependency>
<groupId>com.netflix.feign</groupId>
<artifactId>feign-jackson</artifactId>
<version>8.18.0</version>
</dependency>
2.写代码
以天气api接口为例
controller层
package com.vvvtimes.demo.controller;
import com.vvvtimes.demo.common.dto.RestResponse;
import com.vvvtimes.demo.domain.dto.WeatherCityDTO;
import com.vvvtimes.demo.domain.mybatis.City;
import com.vvvtimes.demo.domain.vo.WeatherVo;
import com.vvvtimes.demo.service.WeatherService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
import java.util.List;
@RestController
@RequestMapping("/weather")
public class WeatherController {
@Autowired
private WeatherService weatherService;
@RequestMapping(value = "city/{id:1[0-9]{8}}", method = {RequestMethod.POST, RequestMethod.GET})
public RestResponse<WeatherVo> loadApi(@PathVariable("id") String id) {
return weatherService.loadApi(id);
}
}
service层
/**
* 获取数据
* @param id
* @return
*/
@Cacheable(cacheNames = "weather_cache", key = "#id")// 从缓存获取，key为ID，缓存具体看 ehcache.xml 配置文件
public RestResponse<WeatherVo> loadApi(String id) {
RestResponse<WeatherVo> result =new RestResponse<>();
WeatherVo weatherVo = sojsonApiClient.getCityWeather(id);
if(weatherVo!=null && weatherVo.isSuccess()){
result.setResult(weatherVo);
}
return result;
}//client层
package com.vvvtimes.demo.client;
import com.vvvtimes.demo.domain.vo.WeatherVo;
import feign.Param;
import feign.RequestLine;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import java.util.Map;
@Component
public interface SojsonApiClient {
//@GetMapping(value = "/api/weather/city/{id}")
@RequestLine("GET /api/weather/city/{id}")
WeatherVo getCityWeather(@Param("id") String id);
}
client拦截器
package com.vvvtimes.demo.client.interception;
import feign.RequestInterceptor;
import feign.RequestTemplate;
public class SojsonInterceptor implements RequestInterceptor {
@Override
public void apply(RequestTemplate requestTemplate) {
}
}
feign配置
package com.vvvtimes.demo.config;
import com.vvvtimes.demo.client.IpinfoApiClient;
import com.vvvtimes.demo.client.SojsonApiClient;
import com.vvvtimes.demo.client.interception.IpinfoInterceptor;
import com.vvvtimes.demo.client.interception.SojsonInterceptor;
import feign.Feign;
import feign.jackson.JacksonDecoder;
import feign.jackson.JacksonEncoder;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class ApiRegisterConfig {
@Value("${sojson.base.url:http://t.weather.sojson.com/}")
private String sojsonRegisterUrl;
@Bean
public SojsonApiClient sojsonApiRegister() {
return Feign.builder().encoder(new JacksonEncoder())
.decoder(new JacksonDecoder())
.requestInterceptor(new SojsonInterceptor())
.target(SojsonApiClient.class, sojsonRegisterUrl);
}
}
3.测试访问
http://localhost:9000/weather/city/101010100
二、spring注解@GetMapping使用
上面使用的注解多少有点别扭，实际上我们可以通过feign-contract Feign的契约方式来使用spring的注解。
这里只对比上的代码讲解改造过程，不给出全代码
1.改造依赖
上面的feign依赖替换如下
<!-- feign -->
<dependency>
<groupId>io.github.openfeign</groupId>
<artifactId>feign-core</artifactId>
<version>11.6</version>
</dependency>
<dependency>
<groupId>io.github.openfeign</groupId>
<artifactId>feign-spring4</artifactId>
<version>11.6</version>
</dependency>
<dependency>
<groupId>io.github.openfeign</groupId>
<artifactId>feign-jackson</artifactId>
<version>11.6</version>
</dependency>
<dependency>
<groupId>io.github.openfeign</groupId>
<artifactId>feign-httpclient</artifactId>
<version>11.6</version>
</dependency>
<dependency>
<groupId>io.github.openfeign.form</groupId>
<artifactId>feign-form</artifactId>
<version>3.8.0</version>
</dependency>2.配置契约
ApiRegisterConfig的Bean加一句.contract(new SpringContract())
对应bean代码如下
@Bean
public SojsonApiClient sojsonApiRegister() {
return Feign.builder().encoder(new JacksonEncoder())
.decoder(new JacksonDecoder())
.requestInterceptor(new SojsonInterceptor())
.contract(new SpringContract())
.target(SojsonApiClient.class, sojsonRegisterUrl);
}3.改注解
将@RequestLine注解改成@GetMapping注解，代码如下
@GetMapping(value = "/api/weather/city/{id}")
//@RequestLine("GET /api/weather/city/{id}")
WeatherVo getCityWeather(@PathVariable("id") String id);至此改造完成。
注意：本文没有设置feign的全局拦截器，因为在第三方接口中，每种接口的鉴权方式不一样，建议每种类型的接口单独设置拦截器做鉴权
