SpringCloud（三）eureka注册中心的使用

ゝ一世哀愁。 2022-10-02 14:50 185阅读 0赞

## 源码 ##

GitHub：[https://github.com/291685399/springcloud-learning/tree/master/springcloud-eureka02][https_github.com_291685399_springcloud-learning_tree_master_springcloud-eureka02]

## eureka是什么？ ##

eureka是Netflix公司开源的注册中心，用于管理生产者和消费者，能够对服务进行服务的自动注册、发现、状态监控

## eureka的原理 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM1NjIwNTAx_size_16_color_FFFFFF_t_70]

> Eureka：就是服务注册中心（可以是一个集群），提供者和消费者暴露地址  
> 提供者：启动后向Eureka注册自己信息（地址，提供什么服务）  
> 消费者：向Eureka订阅服务，Eureka会将对应服务的所有提供者地址列表发送给消费者，并且定期更新  
> 心跳(续约)：提供者定期通过http方式向Eureka刷新自己的状态

## eureka的使用 ##

*  新建一个父工程，命名为springcloud-eureka02

目录结构如下图：  
![在这里插入图片描述][20190621213354731.png]  
pom.xml：

<parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.4.RELEASE</version>
        <relativePath/>
    </parent>
    
    <dependencies>
        
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

*  新建模块，命名为eureka-server02

目录结构如下图：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM1NjIwNTAx_size_16_color_FFFFFF_t_70 1]  
pom.xml：

在启动器EurekaServerApplication上添加注解用于开启eureka server

@SpringBootApplication
    @EnableEurekaServer
    public class EurekaServerApplication { 
        public static void main(String[] args) { 
            SpringApplication.run(EurekaServerApplication.class, args);
        }
    }

在application.properties：

server.port=10000
    spring.application.name:eureka-server
    # 是否注册自己的信息到EurekaServer，默认是true
    eureka.client.register-with-eureka=false
    # 是否拉取其它服务的信息，默认是true
    eureka.client.fetch-registry=false
    # EurekaServer的地址，现在是自己的地址，如果是集群，需要加上其它Server的地址
    eureka.client.service-url.defaultZone:http://127.0.0.1:${server.port}/eureka

*  新建模块，命名为eureka-provider02

目录结构如下图：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM1NjIwNTAx_size_16_color_FFFFFF_t_70 2]

pom.xml：

<parent>
        <groupId>com.wyj</groupId>
        <artifactId>springcloud-eureka02</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    </parent>
    
    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Finchley.SR1</spring-cloud.version>
    </properties>
    
    <dependencies>
        
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
    </dependencies>
    
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

在启动器EurekaProviderApplication上添加注解用于开启eureka client

@SpringBootApplication
    @EnableDiscoveryClient
    public class EurekaProviderApplication { 
        public static void main(String[] args) { 
            SpringApplication.run(EurekaProviderApplication.class, args);
        }
    }

ProviderController：

@Controller
    public class ProviderController { 
    
        @Autowired
        private UserService userService;
    
        @RequestMapping(value = "/findById/{id}")
        @ResponseBody
        public User findById(@PathVariable int id) { 
            User user = userService.findById(id);
            return user;
        }
    }

UserService：

public interface UserService { 
        public User findById(int id);
    }

UserServiceImpl：

@Service
    public class UserServiceImpl implements UserService { 
    
        @Autowired
        private UserRepository userRepository;
    
        @Override
        public User findById(int id) { 
            Optional<User> userOptional = userRepository.findById(id);
            User user = userOptional.get();
            return user;
        }
    }

UserRepository：

public interface UserRepository extends JpaRepository<User, Integer> { 
    }

User：

@Entity
    @Data
    public class User implements Serializable { 
    
        @Id
        @GeneratedValue
        private int id;
        private String name;
        private String sex;
        private int age;
        private String address;
        private String phone;
    }

application.properties：

server.port=8081
    ### datasource ###
    spring.datasource.url=jdbc:mysql://188.131.247.26:3306/springcloud-eureka01?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8&useSSL=true
    spring.datasource.driver-class-name=com.mysql.jdbc.Driver
    spring.datasource.username=root
    spring.datasource.password=root
    ### springdatajpa ###
    #打印出自动生产的SQL，方便调试的时候查看
    spring.jpa.show-sql=true
    #更新数据库表结构
    spring.jpa.hibernate.ddl-auto= update
    #对打印的sql进行格式化，方便查看
    spring.jpa.properties.hibernate.format_sql=true
    spring.jpa.properties.hibernate.use_sql_comments=true
    #指定生成表名的存储引擎为InneoDB
    spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL5InnoDBDialect
    # springcloud
    spring.application.name=eureka-provider
    # EurekaServer地址
    eureka.client.service-url.defaultZone=http://127.0.0.1:10000/eureka
    # 当调用getHostname获取实例的hostname时，返回ip而不是host名称
    eureka.instance.prefer-ip-address=true
    eureka.instance.ip-address=127.0.0.1

*  新建模块，命名为eureka-consumer02

目录结构如下图：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM1NjIwNTAx_size_16_color_FFFFFF_t_70 3]

pom.xml：

<parent>
        <groupId>com.wyj</groupId>
        <artifactId>springcloud-eureka02</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    </parent>
    
    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Finchley.SR1</spring-cloud.version>
    </properties>
    
    <dependencies>
        
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
    </dependencies>
    
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

在启动器EurekaConsumerApplication上添加注解用于开启eureka client

@SpringBootApplication
    @EnableDiscoveryClient
    public class EurekaConsumerApplication { 
        public static void main(String[] args) { 
            SpringApplication.run(EurekaConsumerApplication.class, args);
        }
    }

ConsumerController：

@Controller
    public class ConsumerController{ 
    
        @Autowired
        private RestTemplate restTemplate;
    
        // Eureka客户端，可以获取到服务实例信息
        @Autowired
        private DiscoveryClient discoveryClient;
    
        @RequestMapping(value = "/findById/{id}")
        @ResponseBody
        public User findById(@PathVariable int id) { 
            // 根据服务名称，获取服务实例
            List<ServiceInstance> instances = discoveryClient.getInstances("eureka-provider");
            // 因为只有一个UserService,因此我们直接get(0)获取
            ServiceInstance instance = instances.get(0);
            String baseUrl = "http://" + instance.getHost() + ":" + instance.getPort();
            System.out.println("baseUrl=" + baseUrl);
            User user = restTemplate.getForObject(baseUrl + "/findById/" + id, User.class);
            return user;
        }
    }

RestConfig：

@Configuration
    public class RestConfig { 
    
        @Bean
        public RestTemplate restTemplate() { 
            return new RestTemplate();
        }
    }

User：

@Data
    public class User implements Serializable { 
    
        private int id;
        private String name;
        private String sex;
        private int age;
        private String address;
        private String phone;
    }

application.properties：

server.port=8080
    # springcloud
    spring.application.name=eureka-consumer
    # EurekaServer地址
    eureka.client.service-url.defaultZone=http://127.0.0.1:10000/eureka
    # 当调用getHostname获取实例的hostname时，返回ip而不是host名称
    eureka.instance.prefer-ip-address=true

## 测试使用 ##

分别启动eureka-server、eureka-provider02和eureka-consumer02

*  访问

浏览器访问http://127.0.0.1:8080/findById/1  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM1NjIwNTAx_size_16_color_FFFFFF_t_70 4]

*  访问eureka  
    [http://127.0.0.1:10000/（我这里eureka服务的端口设置为10000，默认是为8761）][http_127.0.0.1_10000_eureka_10000_8761]  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM1NjIwNTAx_size_16_color_FFFFFF_t_70 5]  
    可以看到当前有eureka-consumer和eureka-provider两个实例

## 总结 ##

有了eureka注册中心相比于纯粹使用RestTemplate没有注册中心而言  
1、有了注册中心更加方便管理生产者和消费者，在注册中心页面可以查看到很多信息，比如实例信息，比如注册中心信息  
2、有了注册中心可以动态的获取提供者实例的rest服务路径，然后使用RestTemplate调用生产者的rest服务  
3、注册中心eureka还可以进行集群，提高数据的吞吐量

[https_github.com_291685399_springcloud-learning_tree_master_springcloud-eureka02]: https://github.com/291685399/springcloud-learning/tree/master/springcloud-eureka02
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[20190621213354731.png]: /images/20220109/4c21baa7ffc74c499dadb4ece310c598.png
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM1NjIwNTAx_size_16_color_FFFFFF_t_70 2]: /images/20220109/ef51ab7f238440079d590e555db93875.png
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[http_127.0.0.1_10000_eureka_10000_8761]: http://127.0.0.1:10000/%EF%BC%88%E6%88%91%E8%BF%99%E9%87%8Ceureka%E6%9C%8D%E5%8A%A1%E7%9A%84%E7%AB%AF%E5%8F%A3%E8%AE%BE%E7%BD%AE%E4%B8%BA10000%EF%BC%8C%E9%BB%98%E8%AE%A4%E6%98%AF%E4%B8%BA8761%EF%BC%89
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