2.2注册中心：Eureka

pom.xml配置

<?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.demo</groupid>
<artifactid>eurekaserver</artifactid>
<version>0.0.1-snapshot</version>
<packaging>jar</packaging>

<name>eurekaserver</name>
<description>demo project for spring boot</description>

<parent>
<groupid>org.springframework.boot</groupid>
<artifactid>spring-boot-starter-parent</artifactid>
<version>1.5.2.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>
<!--eureka server -->
<dependency>
<groupid>org.springframework.cloud</groupid>
<artifactid>spring-cloud-starter-eureka-server</artifactid>
</dependency>

<!-- spring boot test-->
<dependency>
<groupid>org.springframework.boot</groupid>
<artifactid>spring-boot-starter-test</artifactid>
<scope>test</scope>
</dependency>
</dependencies>

<dependencymanagement>
<dependencies>
<dependency>
<groupid>org.springframework.cloud</groupid>
<artifactid>spring-cloud-dependencies</artifactid>
<version>dalston.rc1</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>

<repositories>
<repository>
<id>spring-milestones</id>
<name>spring milestones</name>
<url>https://repo.spring.io/milestone</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
</repositories>


</project>

启动一个服务注册中心，只需要一个注解@enableeurekaserver，这个注解需要在springboot工程的启动application类上加：

@enableeurekaserver
@springbootapplication
public class eurekaserverapplication {

public static void main(string[] args) {
springapplication.run(eurekaserverapplication.class, args);
}
}

eureka是一个高可用的组件，它没有后端缓存，每一个实例注册之后需要向注册中心发送心跳（因此可以在内存中完成），在默认情况下erureka server也是一个eureka client ,必须要指定一个 server。eureka server的配置文件application.yml：

server:
port: 8765

eureka:
instance:
hostname: localhost
client:
registerwitheureka: false
fetchregistry: false
serviceurl:
defaultzone: http://${eureka.instance.hostname}:${server.port}/eureka/

通过eureka.client.registerwitheureka：false和fetchregistry：false来表明自己是一个eureka server.

eureka server 是有界面的，启动工程,打开浏览器访问：
 

因为没有注册服务当然不可能有服务被发现了,所以（no application available 没有服务被发现）

第二步创建一个服务提供者 (eureka client)

当client向server注册时，它会提供一些元数据，例如主机和端口，url，主页等。eureka server 从每个client实例接收心跳消息。 如果心跳超时，则通常将该实例从注册server中删除。

pom.xml配置

<?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.forezp</groupid>
<artifactid>service-hi</artifactid>
<version>0.0.1-snapshot</version>
<packaging>jar</packaging>

<name>service-hi</name>
<description>demo project for spring boot</description>

<parent>
<groupid>org.springframework.boot</groupid>
<artifactid>spring-boot-starter-parent</artifactid>
<version>1.5.2.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.cloud</groupid>
<artifactid>spring-cloud-starter-eureka</artifactid>
</dependency>
<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>
</dependencies>

<dependencymanagement>
<dependencies>
<dependency>
<groupid>org.springframework.cloud</groupid>
<artifactid>spring-cloud-dependencies</artifactid>
<version>dalston.rc1</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>

<repositories>
<repository>
<id>spring-milestones</id>
<name>spring milestones</name>
<url>https://repo.spring.io/milestone</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
</repositories>


</project>

通过注解@enableeurekaclient 表明自己是一个eurekaclient.

如:

@value("${server.port}")

string port;

@requestmapping("/hi")

public string home(@requestparam string name) {

return "hi "+name+",i am from port:" +port;

}

仅仅@enableeurekaclient是不够的，还需要在配置文件中注明自己的服务注册中心的地址，application.yml配置文件如下：

eureka:
client:
serviceurl:
defaultzone: http://localhost:8761/eureka/
server:
port: 8762
spring:
application:
name: service-hi

需要指明spring.application.name,这个很重要，这在以后的服务与服务之间相互调用一般都是根据这个name 。