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SpringCloud 系列 --1.Eureka

本贴最后更新于 1700 天前，其中的信息可能已经时过境迁

1.搭建 Eureka 服务端

pom.xml 中添加引用

<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>org.crazyit.cloud</groupId>
	<artifactId>first-ek-server</artifactId>
	<version>0.0.1-SNAPSHOT</version>

	<dependencyManagement>
		<dependencies>
			<dependency>
				<groupId>org.springframework.cloud</groupId>
				<artifactId>spring-cloud-dependencies</artifactId>
				<version>Dalston.SR1</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>
		</dependencies>
	</dependencyManagement>

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

</project>

spring-cloud-starter-eureka-server 会把 spring-boot-starter-web 依赖自动引入,所以同时也支持 web 能力
image.png

启动类添加注解 @EnableEurekaServer

package org.crazyit.cloud;

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

@SpringBootApplication
@EnableEurekaServer
public class FirstServer {

	public static void main(String[] args) {
		new SpringApplicationBuilder(FirstServer.class).run(args);
	}

}

在 resource 目录下面的 applicaiton.yml 文件中指定端口等属性
registerWithEureka: false
是否将自己的信息注册到 Eureka 服务器,默认值 true

fetchRegistry: false
是否到 Eureka 服务器中抓取注册信息,默认值是 true

server:
  port: 8761
eureka:
  client:
    registerWithEureka: false
    fetchRegistry: false
logging:
  level:
    com.netflix: INFO

启动服务浏览器访问如下:
image.png

2.服务提供者

a.pom.xml 中引入依赖

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

完整代码如下:

<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>org.crazyit.cloud</groupId>
	<artifactId>first-ek-service-provider</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	
	<dependencyManagement>
		<dependencies>
			<dependency>
				<groupId>org.springframework.cloud</groupId>
				<artifactId>spring-cloud-dependencies</artifactId>
				<version>Dalston.SR1</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>
		</dependencies>
	</dependencyManagement>

	<dependencies>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-config</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-eureka</artifactId>
		</dependency>
	</dependencies>
	
</project>

b. application.yml 中配置

spring:
  application:
    name: first-service-provider
eureka:
  instance:
    hostname: localhost
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/
logging:
  level:
    com.netflix: INFO

将应用名称配置为 first-server-provider,该服务将会被注册到端口为 8761 的 Eureka 服务器,
eureka.instance.hostname 配置该服务实例的主机名称.

在启动类上面使用 @EnableEurekaClient 注解,声明是一个 Eureka 客户端,

package org.crazyit.cloud;

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

@SpringBootApplication
@EnableEurekaClient
public class FirstServiceProvider {

	public static void main(String[] args) {
		new SpringApplicationBuilder(FirstServiceProvider.class).run(args);
	}
}

编写一个简单的 controller

package org.crazyit.cloud;

import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class FirstController {
	
	@RequestMapping(value = "/person/{personId}", method = RequestMethod.GET, 
			produces = MediaType.APPLICATION_JSON_VALUE)
	public Person findPerson(@PathVariable("personId") Integer personId) {
		Person person = new Person(personId, "Crazyit", 30);
		return person;
	}
}

对应的实体为:

package org.crazyit.cloud;

public class Person {

	private Integer id;
	
	private String name;
	
	private Integer age;

	public Person() {
		super();
	}

	public Person(Integer id, String name, Integer age) {
		super();
		this.id = id;
		this.name = name;
		this.age = age;
	}

	public Integer getId() {
		return id;
	}

	public void setId(Integer id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public Integer getAge() {
		return age;
	}

	public void setAge(Integer age) {
		this.age = age;
	}
	
}

运行后访问 eureka 可以看到我们的实例
image.png

3.服务调用者

pom.xml

<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>org.crazyit.cloud</groupId>
	<artifactId>first-ek-service-invoker</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	
	<dependencyManagement>
		<dependencies>
			<dependency>
				<groupId>org.springframework.cloud</groupId>
				<artifactId>spring-cloud-dependencies</artifactId>
				<version>Dalston.SR1</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>
		</dependencies>
	</dependencyManagement>

	<dependencies>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-config</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-ribbon</artifactId>
		</dependency>
	</dependencies>
</project>

配置文件:

server:
  port: 9000
spring:
  application:
    name: first-service-invoker
eureka:
  instance:
    hostname: localhost
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/

在启动类加上 @EnableDiscoveryClient 注解
注意: @EnableEurekaClient 注解已经包含了 @EnableDiscoveryClient 的功能,也就说,一个 Eureka 客户端,本身就具有服务发现的能力。

package org.crazyit.cloud;

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

@SpringBootApplication
@EnableDiscoveryClient
public class FirstInvoker {

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

编写简单的 Controller

package org.crazyit.cloud;

import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@RestController
@Configuration
public class InvokerController {

	@Bean
	@LoadBalanced
	public RestTemplate getRestTemplate() {
		return new RestTemplate();
	}

	@RequestMapping(value = "/router", method = RequestMethod.GET, 
			produces = MediaType.APPLICATION_JSON_VALUE)
	public String router() {
		RestTemplate restTpl = getRestTemplate();
		// 根据应用名称调用服务
		String json = restTpl.getForObject(
				"http://first-service-provider/person/1", String.class);
		return json;
	}
}

注意: RestTemplate 的 Bean 被 @LoadBalanced 注解修饰后,这个 RESTTemplate 实例就具有访问分布式服务的能力了。

启动服务 eureka 中有两个实例
image.png

并且访问 localhost:9000/router 结果如下:

image.png

  • Spring

    Spring 是一个开源框架，是于 2003 年兴起的一个轻量级的 Java 开发框架，由 Rod Johnson 在其著作《Expert One-On-One J2EE Development and Design》中阐述的部分理念和原型衍生而来。它是为了解决企业应用开发的复杂性而创建的。框架的主要优势之一就是其分层架构，分层架构允许使用者选择使用哪一个组件，同时为 JavaEE 应用程序开发提供集成的框架。

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