spring boot2X整合Consul一使用RestTemplate实现服务调用

Consul可以用于实现分布式系统的服务发现与配置

服务调用有两种方式：

　　A.使用RestTemplate 进行服务调用

　　　　负载均衡——通过Ribbon注解RestTemplate

　　B.使用Feign 进行声明式服务调用

　　　　负载均衡——默认使用Ribbon实现查看

先使用RestTemplate来实现

1.服务注册发现中心

启动Consul

consul agent -dev

2.服务端

在spring boot2X整合Consul 的基础上

添加服务provider，provider1

provider测试方法

package com.xyz.provider.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class demoController {
    @RequestMapping("/hello")
    public String Hello(){
        return "hello,provider";
    }

}

provider1测试方法

package com.xyz.provider1.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class demoController {
    @RequestMapping("/hello")
    public String Hello(){
        return "hello,another provider";
    }
    
}

启动provider和provider1

浏览器访问http://localhost:8500

有两个服务提供者节点实例

3.客户端

（1）添加依赖

<properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Greenwich.SR4</spring-cloud.version>
    </properties>

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

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-consul-discovery</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>

（2）添加配置

server.port=8015
spring.application.name=xyz-comsumer
spring.cloud.consul.host=localhost
spring.cloud.consul.port=8500
spring.cloud.consul.discovery.register=false
spring.cloud.consul.discovery.health-check-url=/actuator/health
spring.cloud.consul.discovery.heartbeat.enabled=true
management.endpoints.web.exposure.include=*
management.endpoint.health.show-details=always

（3）测试方法

获取所有注册的服务，从注册的服务中选取一个，服务调用

package com.xyz.comsumer.controller;

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.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@RestController
public class HelloController {
    @Autowired
    private LoadBalancerClient loadBalancer;
    @Autowired
    private DiscoveryClient discoveryClient;
    private  String serviceName = "service-provider";

    @RequestMapping("/services")
    public Object services() {
        return discoveryClient.getInstances(serviceName);
    }

    @RequestMapping("/discover")
    public Object discover() {
        return loadBalancer.choose(serviceName).getUri().toString();
    }

    @RequestMapping("/hello")
    public String hello() {
        ServiceInstance serviceInstance = loadBalancer.choose(serviceName);
        String callServiceResult = new RestTemplate().getForObject(serviceInstance.getUri().toString() + "/hello", String.class);
        return callServiceResult;
    }
}

注：

　　客户端调用的服务名，是在服务端指定的，在服务端配置里使用 spring.cloud.consul.discovery.service-name指注册到 Consul 的服务名称

测试

启动Consul

启动provider和provider1

启动comsumer

测试地址 http://localhost:8015/services

　　返回结果

[
    {
        "instanceId": "provider-8010",
        "serviceId": "service-provider",
        "host": "hkgi-PC",
        "port": 8010,
        "secure": false,
        "metadata": {
            "secure": "false"
        },
        "uri": "http://hkgi-PC:8010",
        "scheme": null
    },
    {
        "instanceId": "provider-8011",
        "serviceId": "service-provider",
        "host": "hkgi-PC",
        "port": 8011,
        "secure": false,
        "metadata": {
            "secure": "false"
        },
        "uri": "http://hkgi-PC:8011",
        "scheme": null
    }
]

测试地址 http://localhost:8015/discover

返回结果

　　http://hkgi-PC:8011 或 http://hkgi-PC:8011

　　测试地址 http://localhost:8015/hello

　　返回结果

　　hello,provider 或 hello,another provider

注：

　　结果交替出现的，这是因为负载均衡器是采用的是轮询的方式

说明：

　　调用的过程：

　　　　A.通过LoadBalancerClient查询服务

　　　　B.通过RestTemplate调用远程服务

　　Ribbon负载均衡策略

　　　　BestAvailableRule

　　　　AvailabilityFilteringRule

　　　　WeightedResponseTimeRule

　　　　RetryRule

　　　　RoundRobinRule

　　　　RandomRule

　　　　ZoneAvoidanceRule

自定义Ribbon负载均衡——使用随机访问策略

修改启动类

package com.xyz.comsumer;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
public class ComsumerApplication {

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

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

}

服务调用

package com.xyz.comsumer.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@RestController
public class RibbonHelloController {

    @Autowired
    private RestTemplate restTemplate;
    private  String serviceName = "service-provider";

    @RequestMapping("/ribbon/hello")
    public String hello() {
        String callServiceResult = restTemplate.getForObject("http://"+serviceName+"/hello", String.class);
        return callServiceResult;
    }
}

配置添加

service-provider.ribbon.NFLoadBalancerRuleClassName=com.netflix.loadbalancer.RandomRule

重新启动 comsumer

测试地址 http://localhost:8015/ribbon/hello

输出的结果不再是交替出现，改为随机的了