Spring Cloud为Feign添加了Spring MVC的注解支持，并整合了Ribbon和Eureka来为使用Feign时提供负载均衡。
使用Feign
1. 添加依赖
<dependencies> <!--openfein的依赖--> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-openfeign</artifactId> <version>2.1.3.RELEASE</version> </dependency> </dependencies> 2. 启用Feign
启用类上添加注解@EnableFeignClients客户端允许开启使用Feign调用，扫描@FeignClient标注的FeignClient接口
@SpringBootApplication @EnableFeignClients @EnableWeb public class FeignApplication { public static void main(String[] args) { SpringApplication.run(FeignApplication.class,args); } } 3. 编写FeignClient接口
@FeignClient( name = "demo-service", url = "http://localhost:8080/feign/server/", configuration = FeignInterceptor.class, fallback = TestService.DefaultFallback.class ) public interface TestService { @RequestMapping(value = "/getError/{id}", method = RequestMethod.GET) public String getError(@RequestParam("id") Integer id); @RequestMapping(value = "/get1", method = RequestMethod.GET) public String get1(); @RequestMapping(value = "/get2/{param}", method = RequestMethod.GET) public String get2(@RequestParam("param") String param); @RequestMapping(value = "/post1", method = RequestMethod.POST) public FeignDemo post1(@RequestBody FeignDemo demo); 4. 对应的服务端
@RestController @RequestMapping("/feign/server") public class FeignServerController { @GetMapping("/get1") public String get1() { return "get1"; } @GetMapping("/get2/{para}") public String get2(@PathVariable("para") String para){ return para; } @PostMapping("/post1") public FeignDemo post1(@RequestBody FeignDemo demo) { return demo; } @Component public class DefaultFallback implements TestService { @Override public String getError(@RequestParam("id") Integer id){ return ""; } @Override public String get1() { return null; } @Override public String get2(String param) { return null; } @Override public FeignDemo post1(FeignDemo demo) { return null; } } } public class FeignDemo { private String name; private Integer age; public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } @Override public String toString() { return "FeignDemo{" + "name='" + name + '\'' + ", age=" + age + '}'; } } 5. 调用FeignClient
@RunWith(SpringJUnit4ClassRunner.class) @SpringBootTest(classes = {FeignApplication.class},webEnvironment = SpringBootTest.WebEnvironment.DEFINED_PORT) @ActiveProfiles("dev,feign") public class FeignClientTest { @Autowired private TestService testService; @Test public void testFallback(){ testService.getError(1); } @Test public void testGet1(){ System.out.println(testService.get1()); System.out.println(testService.get2("abc")); System.out.printf(".."); FeignDemo feignDemo = new FeignDemo(); feignDemo.setName("name"); feignDemo.setAge(1); System.out.println(testService.post1(feignDemo)); } } 使用Apache的HTTP Client
使用Apache的HTTP Client替换Feign原生httpclient
1. 添加依赖
<!--httpclient的依赖，因为选择了使用httpclient--> <dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpclient</artifactId> </dependency> <dependency> <groupId>io.github.openfeign</groupId> <artifactId>feign-httpclient</artifactId> <version>10.4.0</version> </dependency> 2. 启用
配置中添加如下信息，表示启用httpclient。
feign:
httpclient:
enabled: true
Feign中使用OkHttp
1. 添加依赖
在Feign中使用OkHttp作为网络请求框架，则只需要在pom文件中加上feign-okhttp的依赖，代码如下：
<dependency> <groupId>io.github.openfeign</groupId> <artifactId>feign-okhttp</artifactId> <version>10.2.0</version> </dependency 启用配置
feign:
okhttp:
enabled: true
修改日志级别
在发送和接收请求的时候，将日志的输出定义了四个等级：
| 级别 | 说明 |
|---|---|
| NONE | 不做任何记录 |
| BASIC | 仅记录请求方法和URL以及响应状态代码和执行时间 |
| HEADERS | 记录基本信息以及请求和响应标头 |
| FULL | 记录请求和响应的标题，正文和元数据 |
1. 通过配置
接口的全路径名
logging: level: com.zto.titans.test.feign.service.TestService : DEBUG 2. 通过配置类
@Configuration public class FooConfiguration { @Bean Logger.Level feignLoggerLevel() { return Logger.Level.FULL; } } 数据压缩
feign:
compression:
request:
enabled: true
response:
enabled: true
配置以及配置覆盖
1. 自定义配置类，指定配置
public class TestConfiguration { @Bean Logger.Level feignLoggerLevel() { return Logger.Level.FULL; } } 将TestConfiguration指定到configuration中。
@FeignClient( name = "test-service", configuration = {FeignInterceptor2.class,TestConfiguration.class} ) 2. 配置文件中 default全局配置
feign.client.config.default.xxx ,通过这个default创建全局的配置属性。
feign: client: config: default: connectTimeout: 5000 readTimeout: 5000 loggerLevel: basic 3. 配置文件中专属配置
feign.client.config.feignName.xxx , 按名字指定FeignClient的配置。
feign: client: config: feignName: connectTimeout: 5000 readTimeout: 5000 loggerLevel: full errorDecoder: com.example.SimpleErrorDecoder retryer: com.example.SimpleRetryer requestInterceptors: - com.example.FooRequestInterceptor - com.example.BarRequestInterceptor decode404: false encoder: com.example.SimpleEncoder decoder: com.example.SimpleDecoder 3. 配置的覆盖与追加
org.springframework.cloud.openfeign.FeignClientFactoryBean#configureFeign中可以确认几个配置的优先级：
- 自定义配置类，指定配置
- 配置文件中 default全局配置
- 配置文件中专属配置
configureUsingConfiguration(context, builder); // 1 configureUsingProperties(properties.getConfig().get(properties.getDefaultConfig()),builder); //2 configureUsingProperties(properties.getConfig().get(this.contextId),builder);//3 1. 覆盖的原则
3 -覆盖-> 2 -覆盖-> 1
2. 追加的原则
requestInterceptors不是覆盖的模式，而是追加，从requestInterceptors的执行顺序的优先级看是：
1 > 2 > 3
注意：RequestInterceptor 的实现类，如果使用@Component注解，那么都会被识别到，并在1中添加，若 还在配置中指定了，在2，和3中会继续在requestInterceptors列表中追加，产生重复。
拦截器
RequestInterceptor 就是拦截器 可以在发送前做一些处理，比如统一添加header信息。
其添加的一些规则，上配置追加里有提及
1. 自定义三个RequestInterceptor
class FeignInterceptor implements RequestInterceptor { @Override public void apply(RequestTemplate requestTemplate) { requestTemplate.header("user", "myuser1"); requestTemplate.header("password", "mypassword"); } } class FeignInterceptor1 implements RequestInterceptor { @Override public void apply(RequestTemplate requestTemplate) { requestTemplate.header("user1", "myuser1"); requestTemplate.header("password1", "mypassword1"); } } class FeignInterceptor2 implements RequestInterceptor { @Override public void apply(RequestTemplate requestTemplate) { requestTemplate.header("user2", "myuser2"); requestTemplate.header("password2", "mypassword2"); } } 2. @FeignClient中指定一个
@FeignClient( name = "test-service", url = "http://localhost:8080/feign/server/", configuration = {FeignInterceptor.class,TestConfiguration.class}, fallback = TestService.DefaultFallback.class ) 3. 配置中指定2个
default 指定了一个，test-service里指定一个
feign: httpclient: enabled: true okhttp: enabled: true client: config: default: connectTimeout: 5000 readTimeout: 5000 #loggerLevel: none requestInterceptors: - com.zto.titans.test.feign.service.FeignInterceptor1 test-service: #loggerLevel: basic requestInterceptors: - com.zto.titans.test.feign.service.FeignInterceptor2 logging: level: com.zto.titans.test.feign.service.TestService : DEBUG 根据配置的的追加逻辑，最终执行的顺序是：
1：FeignInterceptor
2：FeignInterceptor1
3：FeignInterceptor2
cat 埋点：
断路器
Feign使用Hystrix
作者：rock_fish
链接：https://www.jianshu.com/p/49accf2167b2
来源：简书
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