Springcloud-Eureka实现服务注册与发现

讲下我的大体流程，分别创建注册中心（spring-cloud-eureka）、服务提供者(spring-cloud-item)、服务调用者(spring-cloud-order)三个服务演示。这里没个服务我只展示主要是类、pom及配置文件。

一、服务搭建过程

1、spring-cloud-eureka

(1)️pom 文件，整个过程中因为springboot和springcloud版本不兼容踩了许多的坑，所以先贴pom文件。

<?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>spring-cloud-eureka</groupId>
    <artifactId>spring-cloud-eureka</artifactId>
    <version>1.0-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.3.RELEASE</version>
    </parent>

    <!-- 导入Spring Cloud的依赖管理 -->
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Finchley.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <dependencies>
        <!-- 导入Eureka服务的依赖 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-autoconfigure</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-commons</artifactId>
            <scope>compile</scope>
        </dependency>
    </dependencies>

    <repositories>
        <repository>
            <id>spring-snapshots</id>
            <name>Spring Snapshots</name>
            <url>https://repo.spring.io/libs-snapshot</url>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </repository>
        <repository>
            <id>spring-releases</id>
            <name>Spring Releases</name>
            <url>https://repo.spring.io/libs-release</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
    </repositories>

    <build>
        <finalName>${project.artifactId}</finalName>
        <plugins>
            <!-- 资源文件拷贝插件 -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-resources-plugin</artifactId>
                <configuration>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
            <!-- java编译插件 -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

(2)application.yml

server:
  port: 6868

eureka:
  client:
    registerWithEureka: false #是否将自己注册到Eureka服务中，本身所以无需注册
    fetchRegistry: false #是否从Eureka中获取注册信息
    serviceUrl: #Eureka客户端与服务端进行交互到地址
      defaultZone: http://127.0.0.1:${server.port}/eureka
  eureka:
    server:
      enable-self-preservation=falsver: false

(3)主类

package spring.cloud.eureka;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

@EnableEurekaServer //用来指定该项目为Eureka的服务注册中心
@SpringBootApplication
public class EurekaServerApplication {

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

更多的注解作用可以参考这篇文章，个人感觉总结很全面：blog.csdn.net/Lang_Perry/…

2、spring-cloud-item

item是服务的提供方，需注册自己的服务到服务中心。 (1) pom.xml

<?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>spring-cloud-eureka</groupId>
    <artifactId>spring-cloud-eureka</artifactId>
    <version>1.0-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.3.RELEASE</version>
    </parent>

    <!-- 导入Spring Cloud的依赖管理 -->
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Finchley.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <dependencies>
        <!-- 导入Eureka服务的依赖 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-autoconfigure</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-commons</artifactId>
            <scope>compile</scope>
        </dependency>
    </dependencies>

    <repositories>
        <repository>
            <id>spring-snapshots</id>
            <name>Spring Snapshots</name>
            <url>https://repo.spring.io/libs-snapshot</url>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </repository>
        <repository>
            <id>spring-releases</id>
            <name>Spring Releases</name>
            <url>https://repo.spring.io/libs-release</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
    </repositories>

    <build>
        <finalName>${project.artifactId}</finalName>
        <plugins>
            <!-- 资源文件拷贝插件 -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-resources-plugin</artifactId>
                <configuration>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
            <!-- java编译插件 -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

(2)application.yml

server:
  port: 8081 #服务端口

spring:
  application:
    name: spring-cloud-item #指定服务名

eureka:
  client:
    registerWithEureka: true #是否将自己注册到Eureka服务中，默认为true
    fetchRegistry: true #是否从Eureka中获取注册信息，默认为true
    serviceUrl: #Eureka客户端与Eureka服务端进行交互的地址
      defaultZone: http://127.0.0.1:6868/eureka/
  instance:
    prefer-ip-address: true #将自己的ip地址注册到Eureka服务中

(3)主类

package spring.cloud.item;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

@EnableDiscoveryClient //让服务使用eureka服务器 实现服务注册和发现
@SpringBootApplication
public class ItemApplication {

    public static void main(String[] args) {
        SpringApplication.run(ItemApplication.class, args);
    }
}

3、spring-cloud-order

服务调用者，调用item获取具体商品信息 (1)pom.xml

<?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>spring-cloud-order</groupId>
    <artifactId>spring-cloud-order</artifactId>
    <version>1.0-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.6.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-autoconfigure</artifactId>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>

        <dependency>
            <groupId>com.squareup.okhttp3</groupId>
            <artifactId>okhttp</artifactId>
            <version>3.9.0</version>
        </dependency>
        <!-- 导入Eureka服务的依赖 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
            <exclusions>
                <exclusion>
                    <groupId>com.fasterxml.jackson.dataformat</groupId>
                    <artifactId>jackson-dataformat-xml</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-commons</artifactId>
            <scope>compile</scope>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Finchley.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <finalName>${project.artifactId}</finalName>
        <plugins>
            <!-- 资源文件拷贝插件 -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-resources-plugin</artifactId>
                <configuration>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
            <!-- java编译插件 -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

(2)application.yml

server:
  port: 8082

cloud:
  item:
    url: http://127.0.0.1:8081/item/

spring:
  application:
    name: spring-cloud-order #指定服务名

eureka:
  client:
    registerWithEureka: false #是否将自己注册到Eureka服务中，默认为true
    fetchRegistry: false #是否从Eureka中获取注册信息，默认为true
    serviceUrl: #Eureka客户端与Eureka服务端进行交互的地址
      defaultZone: http://127.0.0.1:6868/eureka/

(3)主类

package spring.cloud.order;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

@EnableDiscoveryClient
@SpringBootApplication
public class OrderApplication {

    public static void main(String[] args) {
        SpringApplication.run(OrderApplication.class, args);
    }
}

下面是order服务中调用到方式，service层示例：

@Service
@Slf4j
public class ItemService {
    
    @Autowired
    private RestTemplate restTemplate;
//在使用服务注册中心之前，是将服务提供方到地址直接配置在yml中，这里获取调用的
//    @Autowired
//    private OrderProperties orderProperties;
    @Autowired
    private DiscoveryClient discoveryClient;

    public Item queryItemById(Long id) {
        String serviceId = "spring-cloud-item";
        List<ServiceInstance> instances = this.discoveryClient.getInstances(serviceId);
        if(instances.isEmpty()){
            return null;
        }
        ServiceInstance serviceInstance = instances.get(0);
        log.info("get serviceInstance——>{}", serviceInstance.toString());
        String url = serviceInstance.getHost() + ":" + serviceInstance.getPort();
        log.info("get service url->{}", url);
    //先前调用方式
    //  return this.restTemplate.getForObject(orderProperties.getUrl()+id, Item.class);
        return this.restTemplate.getForObject("http://" + url + "/item/" + id, Item.class);
        
    }
}

下面说说我踩到的坑： 问题1:版本不兼容问题：

java.lang.NoSuchMethodError: org.springframework.boot.builder.SpringApplicationBuilder.<init>([Ljava/lang/Object;)V
    at org.springframework.cloud.bootstrap.BootstrapApplicationListener.bootstrapServiceContext(BootstrapApplicationListener.java:157)
    at org.springframework.cloud.bootstrap.BootstrapApplicationListener.onApplicationEvent(BootstrapApplicationListener.java:98)
    at org.springframework.cloud.bootstrap.BootstrapApplicationListener.onApplicationEvent(BootstrapApplicationListener.java:64)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:127)
    at org.springframework.boot.context.event.EventPublishingRunListener.environmentPrepared(EventPublishingRunListener.java:74)
    at org.springframework.boot.SpringApplicationRunListeners.environmentPrepared(SpringApplicationRunListeners.java:54)
    at org.springframework.boot.SpringApplication.prepareEnvironment(SpringApplication.java:351)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:317)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1246)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1234)
    at com.waterlufei.ServiceAApplication.main(ServiceAApplication.java:12)
 
Process finished with exit code 1

启动注册中心直接找不到方法异常，是因为我的springboot版本和cloud版本不兼容，出现这个问题，调整两者的版本即可.如果你不知道，戳它：start.spring.io/actuator/in… 问题2:也可以说是版本原因，我用上面的最终版版本，但是eureka的依赖我使用了下面这个：

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka-server</artifactId>
        </dependency>

version匹配了，这个也得匹配，否者会出现注解导入不了的错误，直接编译出错， 正确的：

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>

不同的springcloud版本对应的artifactId是不一样的，这个很坑，而且不太好排查问题。此外服务的版本不一致，还可能导致服务注册失败。避免这种问题的最好方法就是用个父项目，然后在各个子项目中引入，我的写法比较懒省事，只是单纯的想实验一下，正式服务中可以抽取。 此外，我在pom中服务提供这和消费者中排除了dataformat

            <exclusions>
                <exclusion>
                    <groupId>com.fasterxml.jackson.dataformat</groupId>
                    <artifactId>jackson-dataformat-xml</artifactId>
                </exclusion>
            </exclusions>

这个的作用只是让我们的返回结果以json形式显示，如果不加，返回的结果将以xml呈现。