Spring Cloud為Feign添加了Spring MVC的注解支持，並整合了Ribbon和Eureka來為使用Feign時提供負載均衡。
使用Feign
1. 添加依賴
<dependencies> <!--openfein的依賴--> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-openfeign</artifactId> <version>2.1.3.RELEASE</version> </dependency> </dependencies> 2. 啟用Feign
啟用類上添加注解@EnableFeignClients客戶端允許開啟使用Feign調用，掃描@FeignClient標注的FeignClient接口
@SpringBootApplication @EnableFeignClients @EnableWeb public class FeignApplication { public static void main(String[] args) { SpringApplication.run(FeignApplication.class,args); } } 3. 編寫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. 對應的服務端
@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. 調用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替換Feign原生httpclient
1. 添加依賴
<!--httpclient的依賴，因為選擇了使用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. 啟用
配置中添加如下信息，表示啟用httpclient。
feign:
httpclient:
enabled: true
Feign中使用OkHttp
1. 添加依賴
在Feign中使用OkHttp作為網絡請求框架，則只需要在pom文件中加上feign-okhttp的依賴，代碼如下：
<dependency> <groupId>io.github.openfeign</groupId> <artifactId>feign-okhttp</artifactId> <version>10.2.0</version> </dependency 啟用配置
feign:
okhttp:
enabled: true
修改日志級別
在發送和接收請求的時候，將日志的輸出定義了四個等級：
| 級別 | 說明 |
|---|---|
| NONE | 不做任何記錄 |
| BASIC | 僅記錄請求方法和URL以及響應狀態代碼和執行時間 |
| HEADERS | 記錄基本信息以及請求和響應標頭 |
| FULL | 記錄請求和響應的標題，正文和元數據 |
1. 通過配置
接口的全路徑名
logging: level: com.zto.titans.test.feign.service.TestService : DEBUG 2. 通過配置類
@Configuration public class FooConfiguration { @Bean Logger.Level feignLoggerLevel() { return Logger.Level.FULL; } } 數據壓縮
feign:
compression:
request:
enabled: true
response:
enabled: true
配置以及配置覆蓋
1. 自定義配置類，指定配置
public class TestConfiguration { @Bean Logger.Level feignLoggerLevel() { return Logger.Level.FULL; } } 將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 ,通過這個default創建全局的配置屬性。
feign: client: config: default: connectTimeout: 5000 readTimeout: 5000 loggerLevel: basic 3. 配置文件中專屬配置
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. 配置的覆蓋與追加
org.springframework.cloud.openfeign.FeignClientFactoryBean#configureFeign中可以確認幾個配置的優先級：
- 自定義配置類，指定配置
- 配置文件中 default全局配置
- 配置文件中專屬配置
configureUsingConfiguration(context, builder); // 1 configureUsingProperties(properties.getConfig().get(properties.getDefaultConfig()),builder); //2 configureUsingProperties(properties.getConfig().get(this.contextId),builder);//3 1. 覆蓋的原則
3 -覆蓋-> 2 -覆蓋-> 1
2. 追加的原則
requestInterceptors不是覆蓋的模式，而是追加，從requestInterceptors的執行順序的優先級看是：
1 > 2 > 3
注意：RequestInterceptor 的實現類，如果使用@Component注解，那么都會被識別到，並在1中添加，若 還在配置中指定了，在2，和3中會繼續在requestInterceptors列表中追加，產生重復。
攔截器
RequestInterceptor 就是攔截器 可以在發送前做一些處理，比如統一添加header信息。
其添加的一些規則，上配置追加里有提及
1. 自定義三個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中指定一個
@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個
default 指定了一個，test-service里指定一個
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 根據配置的的追加邏輯，最終執行的順序是：
1：FeignInterceptor
2：FeignInterceptor1
3：FeignInterceptor2
cat 埋點：
斷路器
Feign使用Hystrix
作者：rock_fish
鏈接：https://www.jianshu.com/p/49accf2167b2
來源：簡書
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