SpringCloud (Finchley version) Tutorial (a): registration services and discovery Eureka

A, spring cloud Introduction

The current version of spring cloud of updates to Finchley, supported version springbott2.0 above. Specific versions can refer to the following table.

Cloud Code	Boot version (train)	Boot version (tested)	lifecycle
Angle	1.2.x	incompatible with 1.3	EOL in July 2017
Brixton	1.3.x	1.4.x	2017-07 Degree
Camden	1.4.x	1.5.x	-
Dalston	1.5.x	not expected 2.x	-
Edgware	1.5.x	not expected 2.x	-
Finchley	2.x	not expected 1.5.x	-

Finchley version of the official document links:

http://cloud.spring.io/spring-cloud-static/Finchley.RELEASE/single/spring-cloud.html

Second, create a registry service
here, I'm still using Component Eureka as a service registration and discovery, as to be out after Consul article details.

2.1 First create a maven main project.

First, create a master Maven project, dependent on the introduction of its pom file, spring Boot version 2.0.3.RELEASE, Spring Cloud version Finchley.RELEASE. The parent pom pom file as a file, play the role of dependent version control, other module works inherit the pom. This series of articles all adopt this model, pom other articles like this pom. Explain again, is not repeated introduction. code show as below:

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <project xmlns="http://maven.apache.org/POM/4.0.0"
 3          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 5     <modelVersion>4.0.0</modelVersion>
 6 
 7     <groupId>com.liu</groupId>
 8     <artifactId>SpringCloudLearn01</artifactId>
 9     <version>1.0-SNAPSHOT</version>
10 
11     <name>sc-f-chapter1</name>
12     <description>Demo project for Spring Boot</description>
13 
14     <parent>
15         <groupId>org.springframework.boot</groupId>
16         <artifactId>spring-boot-starter-parent</artifactId>
17         <version>2.0.3.RELEASE</version>
18         <relativePath/>
19     </parent>
20 
21     <modules>
22         <module>eureka-server</module>
23         <module>service-client</module>
24         <module>serice-feign</module>
25     </modules>
26 
27     <properties>
28         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
29         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
30         <java.version>1.8</java.version>
31         <spring-cloud.version>Finchley.RELEASE</spring-cloud.version>
32     </properties>
33 
34     <dependencies>
35         <dependency>
36             <groupId>org.springframework.boot</groupId>
37             <artifactId>spring-boot-starter-test</artifactId>
38             <scope>test</scope>
39         </dependency>
40     </dependencies>
41 
42     <dependencyManagement>
43         <dependencies>
44             <dependency>
45                 <groupId>org.springframework.cloud</groupId>
46                 <artifactId>spring-cloud-dependencies</artifactId>
47                 <version>${spring-cloud.version}</version>
48                 <type>pom</type>
49                 <scope>import</scope>
50             </dependency>
51         </dependencies>
52     </dependencyManagement>
53 
54     <build>
55         <plugins>
56             <plugin>
57                 <groupId>org.springframework.boot</groupId>
58                 <artifactId>spring-boot-maven-plugin</artifactId>
59             </plugin>
60         </plugins>
61     </build>
62 
63 </project>

2.2 Then create two model projects: ** a model project as a service registry, namely Eureka Server, and the other as Eureka Client.

Below to create a server as an example, the process of creating a detailed description:

Right Project -> Create model-> select spring initialir below:

The next step -> select cloud discovery-> eureka server, and then been next on the list.

After the project is created, it inherits the parent pom file pom.xml, and the introduction of dependent spring-cloud-starter-netflix-eureka-server, the code is as follows:

<?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>
    <parent>
        <groupId>com.liu</groupId>
        <artifactId>SpringCloudLearn01</artifactId>
        <version>1.0-SNAPSHOT</version>
    </parent>

    <groupId>com.liu.example</groupId>
    <artifactId>config-client</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>config-client</name>
    <description>Demo project for Spring Boot</description>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-config</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

</project>

2.3 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：

package com.liu.example.eurekaserver;

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

@SpringBootApplication
@EnableEurekaServer
public class EurekaServerApplication {

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

}

**2.4 **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appication.yml：

server:
  port: 8761

#通过eureka.client.registerWithEureka：false和fetchRegistry：false来表明自己是一个eureka server.
eureka:
  instance:
    hostname: localhost
  client:
    registerWithEureka: false
    fetchRegistry: false
    serviceUrl:
      defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/

spring:
  application:
    name: eurka-server

2.5 eureka server 是有界面的，启动工程,打开浏览器访问：
http://localhost:8761 ,界面如下：

No application available 没有服务被发现 ……_
因为没有注册服务当然不可能有服务被发现了。

三、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。

创建过程同server类似,创建完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>
    <parent>
        <groupId>com.liu</groupId>
        <artifactId>SpringCloudLearn01</artifactId>
        <version>1.0-SNAPSHOT</version>
    </parent>

    <groupId>com.liu.example</groupId>
    <artifactId>service-client</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>service-client</name>
    <description>Demo project for Spring Boot</description>

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

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

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

package com.liu.example.serviceclient;

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

@SpringBootApplication
@EnableEurekaClient
public class ServiceClientApplication {

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

}

新建service类型写上一个方法：

package com.liu.example.serviceclient.service;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.Mapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class helloSevice {

    @Value("${server.port}")
    String port;

    @RequestMapping("/hi")
    public String getHello(){
        return "hello! 我的端口号是：" + 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：

server:
  port: 8762
spring:
  application:
    name: service-client

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/

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 。
启动工程，打开http://localhost:8761 ，即eureka server 的网址：

你会发现一个服务已经注册在服务中了，服务名为SERVICE-HI ,端口为7862

这时打开 http://localhost:8762/hi?name=forezp ，你会在浏览器上看到 :

源码下载：https://github.com/MrLiu1227/MySpringCloud.git

SpringCloud (Finchley version) Tutorial (a): registration services and discovery Eureka

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