1. Eureka

1.1 關于Eureka

為springcloud提供了Eureka服務端和客戶端，主要用于服務管理，

Eureka架構：

1.2 搭建Eureka服務器

創建一個專案ServerDemo：

需要匯入的jar包：

<dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Dalston.SR3</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-server</artifactId>
        </dependency>
    </dependencies>

分別是springcloud和eureka服務端的依賴包，

在resources包下創建application.yml組態檔：

server:
  port: 8761
eureka:
  client: 
    register-with-eureka: false
    fetch-registry: false

禁止自己當做服務注冊

register-with-eureka: false

屏蔽注冊資訊

fetch-registry: false

在java包下創建ServerApp.java：

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 ServerApp {

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

}

@EnableEurekaServer：將專案作為SpringCloud中的注冊中心，

運行專案：

這樣我們服務器就搭建好了，

1.3 建立服務提供者 

創建專案ServerPolice，

匯入jar包：

<dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Dalston.SR3</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>

在resources包下創建application.yml組態檔：

spring:
  application:
    name: first-police
eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/

創建PoliceServer.java檔案：

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 PoliceServer {

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

}

@EnableEurekaClient：與服務器配合向外提供注冊與發現服務介面，

創建物體類Police.java：

package org.crazyit.cloud;

public class Police {

    private Integer id;
    private String name;
    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;
    }
    
}

創建PoliceController.java：

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 PoliceController {

    @RequestMapping(value = "/call/{id}", method = RequestMethod.GET, 
            produces = MediaType.APPLICATION_JSON_VALUE)
    public Police call(@PathVariable Integer id) {
        Police p = new Police();
        p.setId(id);
        p.setName("angus");
        return p;
    }
}

運行程式：

可以看到多了一個叫first-police的服務，

也可以直接呼叫這個服務：

1.4  建立服務呼叫者

創建專案PersonClient

匯入jar包：

<dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Dalston.SR3</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>

組態檔application.yml：

server:
  port: 8081
spring:
  application:
    name: first-person
eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/

創建PersonServer.java：

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 PersonServer {

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

}

創建TestController.java：

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.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.client.RestTemplate;

@Controller
@Configuration
public class TestController {
    
    @Bean
    @LoadBalanced
    public RestTemplate getRestTemplate() {
        return new RestTemplate();
    }

    @GetMapping("/router")
    @ResponseBody
    public String router() {
        RestTemplate tpl = getRestTemplate();
        String json = tpl.getForObject("http://first-police/call/1", String.class);
        return json;
    }

}

運行程式：

最終的程式結構：

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