前言
项目准备
1、创建项目feign-consumer
2、继续使用之前的服务提供者hello-service
1、简单的声明式服务调用
1.1、pom
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-eureka</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-feign</artifactId>
</dependency> <?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.didispace</groupId>
<artifactId>feign-consumer</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>feign-consumer</name>
<description>Demo project for Spring Boot</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.3.7.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-eureka</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-feign</artifactId>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>Brixton.SR5</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project> 1.2、注解开启 spring cloud feign申明式服务调用功能
@EnableFeignClients //开启声明式服务调用
@EnableFeignClients
@EnableDiscoveryClient
@SpringBootApplication
public class ConsumerApplication {
public static void main(String[] args) {
SpringApplication.run(ConsumerApplication.class, args);
}
} 1.3、定义HelloService接口
#### 通过@FeignClient 注解指定服务名称来绑定服务 #### 然后通过springMVc 注解绑定服务提供者提供的REST接口，和服务提供者中的url是一模一样哦
@FeignClient(name="HELLO-SERVICE")
public interface HelloService {
@RequestMapping("/hello")
String hello();
} 1.4、Controller 通过调用上面的接口来实现从本客户端发起对hello-service服务接口的hello的调用
//这里用来测试对feign客户端的调用
@RestController
public class ConsumerController {
@Autowired
HelloService helloService;
@RequestMapping(value = "/feign-consumer", method = RequestMethod.GET)
public String helloConsumer() {
return helloService.hello();
}
} 1.5、同ribbon实现的服务消费一样，需要指定服务的注册中心
spring.application.name=feign-consumer
server.port=9001
eureka.client.serviceUrl.defaultZone=http://localhost:1111/eureka/ 1.6、开始验证，浏览器中访问http://localhost:9001/feign-consumer
2、参数绑定
2.1、为了验证参数绑定，再服务提供者中再添加一些方法
@RestController
public class HelloController {
private final Logger logger = Logger.getLogger(getClass());
@Autowired
private DiscoveryClient client;
@RequestMapping(value = "/hello", method = RequestMethod.GET)
public String hello() {
ServiceInstance instance = client.getLocalServiceInstance();
logger.info("/hello, host:" + instance.getHost() + ", service_id:" + instance.getServiceId());
return "Hello World";
}
@RequestMapping(value = "/hello1", method = RequestMethod.GET)
String hello(@RequestParam("name") String name) {
return "hello" +name;
}
@RequestMapping(value = "/hello2", method = RequestMethod.GET)
User hello(@RequestHeader("name") String name, @RequestHeader("age") Integer age){
return new User(name,age);
}
@RequestMapping(value = "/hello3", method = RequestMethod.POST)
String hello(@RequestBody User user){
return "hello"+user.getName()+","+user.getAge();
}
} 2.2、在声明式服务调用的service接口中添加如下， 同时要创建和上面一模一样的User类
#### 注意点：下面注解中的value绝对不仅能为空，这是因为它和feign合作了
//绑定服务提供者，并使用spirngMvc 注解绑定具体REST接口
@FeignClient(name="HELLO-SERVICE")
public interface HelloService {
@RequestMapping("/hello")
String hello();
@RequestMapping(value = "/hello1", method = RequestMethod.GET)
String hello(@RequestParam("name") String name) ;
@RequestMapping(value = "/hello2", method = RequestMethod.GET)
User hello(@RequestHeader("name") String name, @RequestHeader("age") Integer age);
@RequestMapping(value = "/hello3", method = RequestMethod.POST)
String hello(@RequestBody User user);
} 2.3、Controller 调用声明式服务传参开始吧
@RequestMapping(value = "/feign-consumer2", method = RequestMethod.GET)
public String helloConsumer2() {
StringBuilder sb = new StringBuilder();
sb.append(helloService.hello()).append("\n");
sb.append(helloService.hello("DIDI")).append("\n");
sb.append(helloService.hello("DIDI", 30)).append("\n");
sb.append(helloService.hello(new User("DIDI", 30))).append("\n");
return sb.toString();
} 2.4、开始验证，浏览器中访问
3、继承特性，解决User不同位置的问题
解释：
1、这个时候我们会发现，在声明式服务中的User和服务提供者中的User的内容一抹一样，但是位置却不是一样的，所以这样很不利于维护，因为修改了一处，还要继续去修改另外的一处。
2、在声明式@FeginClient中提供的接口其实服务提供者也可以使用。所以，请看下面
3.1、创建一个maven项目 hello-service-api
3.1.1 、pom.xml如下
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.didispace</groupId>
<artifactId>hello-service-api</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>hello-service-api</name>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.3.7.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
</dependencies>
</project> 3.1.2、将2中的User复制过来
3.1.3、将声明式服务调用中的接口类HelloService 复制过来，还要做一番修改哦
1、将头部前缀修改为refactor
2、url路径也修改更名为hello4 5 6
@RequestMapping("/refactor")
public interface HelloService {
@RequestMapping(value = "/hello4", method = RequestMethod.GET)
String hello(@RequestParam("name") String name) ;
@RequestMapping(value = "/hello5", method = RequestMethod.GET)
User hello(@RequestHeader("name") String name, @RequestHeader("age") Integer age);
@RequestMapping(value = "/hello6", method = RequestMethod.POST)
String hello(@RequestBody User user);
} 3.2、开始对服务提供者进行重构
3.2.1、在hellop-service项目pom.xml中引入hello-service-api的依赖,一定要记得对它进行mvn install
<dependency>
<groupId>com.didispace</groupId>
<artifactId>hello-service-api</artifactId>
<version>0.0.1-SNAPSHOT</version>
</dependency> 3.2.2、2、重点来了，创建controller类基础上面的HelloService,没有必要在加@RequestMapping，但是其他的是一定要加的
@RestController
public class RefactorHelloController implements HelloService{
public String hello(@RequestParam("name") String name) {
return "hello" +name;
}
public User hello(@RequestHeader("name") String name, @RequestHeader("age") Integer age){
return new User(name,age);
}
public String hello(@RequestBody User user){
return "hello"+user.getName()+","+user.getAge();
}
} 3.3、下面开始对声明式服务调用开始改造
3.3.1、引入pom依赖
<dependency>
<groupId>com.didispace</groupId>
<artifactId>hello-service-api</artifactId>
<version>0.0.1-SNAPSHOT</version>
</dependency> 3.3.2、绑定服务提供者，接口让他来继承HelloService，这样就保证了和服务提供者中的R EST是一致的了
//绑定服务提供者
@FeignClient(name="HELLO-SERVICE")
public interface RefactorHelloService extends HelloService {
} 3.3.3、Controller开测
//这里用来测试对feign客户端的调用
@RestController
public class ConsumerController {
@Autowired
RefactorHelloService refactorHelloService;
/**
* 2、测试传参
*/
@RequestMapping(value = "/feign-consumer2", method = RequestMethod.GET)
public String helloConsumer2() {
StringBuilder sb = new StringBuilder();
sb.append(refactorHelloService.hello("DIDI")).append("\n");
sb.append(refactorHelloService.hello("DIDI", 30)).append("\n");
sb.append(refactorHelloService.hello(new User("DIDI", 30))).append("\n");
return sb.toString();
}
} 3.3.4、开始测试，浏览器访问 http://localhost:9001/feign-consumer2 成功
4、服务降级配置，类似于断路器(使用3中的项目开发)
4.1、声明式服务调用项目中添加service
HelloServiceFallback，使它实现HelloService 用来作为当调用服务提供者失败后返回的内容
@Component
public class HelloServiceFallback implements HelloService {
@Override
public String hello(@RequestParam("name") String name) {
return "error";
}
@Override
public User hello(@RequestHeader("name") String name, @RequestHeader("age") Integer age) {
return new User("未知", 0);
}
@Override
public String hello(@RequestBody User user) {
return "error";
}
} 4.2、@Feign 绑定服务的时候就开始，添加降级配置
//绑定服务提供者，并使用spirngMvc 注解绑定具体REST接口
@FeignClient(name="HELLO-SERVICE" ,fallback =HelloServiceFallBack.class )
public interface HelloService {
@RequestMapping("/hello")
String hello();
@RequestMapping(value = "/hello1", method = RequestMethod.GET)
String hello(@RequestParam("name") String name) ;
@RequestMapping(value = "/hello2", method = RequestMethod.GET)
User hello(@RequestHeader("name") String name, @RequestHeader("age") Integer age);
@RequestMapping(value = "/hello3", method = RequestMethod.POST)
String hello(@RequestBody User user);
}