spring-cloud呼叫服務有兩種方式，一種是Ribbon+RestTemplate, 另外一種是Feign。
Ribbon是一個基於HTTP和TCP客戶端的負載均衡器，其實feign也使用了ribbon, 只要使用@FeignClient時，ribbon就會自動使用。

Ribbon+RestTemplate實現服務呼叫

1.建立服務註冊中心

前面章節已經介紹過，如不熟悉請檢視

2.建立服務，並註冊帶註冊中心

將http://blog.csdn.net/forwujinwei/article/details/72800571建立的應用複製一份，修改application.properties中的埠號為9001
**注意：在這裡我踩了一個坑，請不要將spring.application.name=eureka.client.01,在後續的呼叫中會報錯，就是因為.01，請不要使用還有數字的註冊方式，只要保證兩個應用的spring.application.name相同就可實現負載均衡測試，在eureka主頁面就可以看到是否註冊成功。**
 

3.建立服務發現應用，並呼叫服務

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>com.example</groupId>
    <artifactId>server</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>spring-cloud-server</name>
    <description>Demo project for Spring Boot</description
 
>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.4.3.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>1.7</java.version>
        <spring-cloud.version>Camden.SR4</spring-cloud.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-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
           <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-ribbon</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</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>
</project>

application.properties

server.port=9090
spring.application.name=eureka.client.02   #別這麼命名，會死的莫名其妙，在這裡不呼叫，我就不做修改了
eureka.client.serviceUrl.defaultZone=http://127.0.0.1:8761/eureka/

入口類：

package com.example;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.context.annotation.Bean;
import org.springframework.http.client.SimpleClientHttpRequestFactory;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
@EnableDiscoveryClient
public class SpringCloudClientDiscoveryApplication {
    @Bean
    @LoadBalanced
    RestTemplate restTemplate(){
         RestTemplate template = new RestTemplate();
            SimpleClientHttpRequestFactory factory = (SimpleClientHttpRequestFactory) template.getRequestFactory();
            factory.setConnectTimeout(3000);
            factory.setReadTimeout(3000);
            return template;
    }

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

呼叫類，為方便測試使用controller類
package com.example.controller;

import java.util.List;

import javax.websocket.server.PathParam;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
import org.springframework.cloud.netflix.ribbon.RibbonClient;
import org.springframework.util.CollectionUtils;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;
import com.example.Consten;

@RestController
public class DiscoveryController {
@Autowired
private RestTemplate restTemplate;
@Autowired
private LoadBalancerClient loadBanlancerClient;
@RequestMapping(“/hi”)
public String hi(){
return restTemplate.getForObject(“http://eureka.client/person/get“, String.class);
}
}
補充下服務類：

package com.example.controller;

import javax.websocket.server.PathParam;

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

@RestController
@RequestMapping("/person")
public class PersonController {
     @Value("${server.port}")
      String port;
    @RequestMapping(value="/get",method=RequestMethod.GET)
    public String getPerson1(){
        return port;//方便觀測負載
    }
}

4.訪問驗證負載均衡

5總結

到這裡spring cloud在開發中的主幹內容已經聯通，也就是第一階段基本已經結束，接下來研究斷路器hystrix/zuul,至於feign服務的呼叫將不在這裡闡述，生產中不常用。

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