Java负载均衡是什么？

将负载（工作任务，访问请求）进行分摊到多个操作单元（服务器，组件）上执行
服务端：服务提供端，比如nginx负载均衡客户端：服务请求方，在发送请求之前已经选好了由哪个实例处理请求。

Spring Cloud Ribbon 是 Netflix Ribbon 实现的一套客户端负载均衡工具

ribbon：Ribbon是Netflix开发客户端负载均衡器，基于某种负载均衡服务消费者去请求提供者。

springcloud提供负载均衡的组件，用注解来完成

定义：负载均衡是由多台服务器以对称的方式组成一个服务器集合，每台服务器都具有等价的地位，都可以单独对外供应效力而无须其他服务器的辅助。经过某种负载分管技术，将外部发送来的央求均匀分配到对称结构中的某一台服务器上，而接收到央求的服务器独登时回应客户的央求。均衡负载可以平均分配客户央求到服务器列阵，籍此供应快速获取重要数据，解决很多并发访问效力问题。这种群集技术可以用最少的出资取得接近于大型主机的性能。

Ribbon 本地负载均衡客户端 VS Nginx 服务端负载均衡区别

Nginx 是服务器负载均衡，客户端所有请求都会交给nginx，然后 nginx 实现转发请求。即负载均衡是由服务端实现的。 Ribbon 本地负载均衡，在调用微服务接口的时候，会在注册中心上获取注册信息服务列表后缓存到JVM 本地，从而在本地实现RPC远程服务调用技术。

下面进行实战

1、测试结果
第一个服务请求了五次

第二个服务请求了三次
这就是负载均衡，还可以继续增加服务

2、两个生产者，这里只是有两个启动类达到生成者的目的，其他和正常服务差不多,没有什么特殊之处，重点看消费者
1 NacosProviderController

@RestController
@Slf4j
public class NacosProviderController {
	@GetMapping("/provider")
	public String provider() {
		System.out.println("==================hello");
		return "（provider invoke这里是提供者提供资源）-" + now();
	}

}

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2 NacosProviderApplication

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class NacosProviderApplication {


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


}

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3 NacosProviderApplication2

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class NacosProviderApplication2 {


	public static void main(String[] args) {
		SpringApplication.run(NacosProviderApplication2.class, args);
	}


}

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4 application.yml

server:
  port: 8086
spring:
  application:
    name: nacos-provider
  cloud:
    nacos:
      discovery:
        server-addr: 127.0.0.1:8848
logging:
  level:
    root: info
    org.springframework: info

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5 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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.3.1.RELEASE</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>cn.nacos.provider</groupId>
	<artifactId>nacos-provider</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>nacos-provider</name>
	<description>Demo project for Spring Boot</description>

	<properties>
		<java.version>1.8</java.version>
	</properties>

	<dependencies>
		<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>
			<exclusions>
				<exclusion>
					<groupId>org.junit.vintage</groupId>
					<artifactId>junit-vintage-engine</artifactId>
				</exclusion>
			</exclusions>
		</dependency>

		<!--nacos依赖-->
		<dependency>
			<groupId>com.alibaba.cloud</groupId>
			<artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
			<version>2.0.1.RELEASE</version>
		</dependency>

		<!--openfeign依赖-->
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-openfeign</artifactId>
			<version>2.1.1.RELEASE</version>
		</dependency>
		<dependency>
			<groupId>org.projectlombok</groupId>
			<artifactId>lombok</artifactId>
			<version>1.18.12</version>
		</dependency>
	</dependencies>

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

</project>

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3、消费者
先看看核心代码

nacos-provider是生成者服务

接下来上全部代码 1、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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>cn.nacos.consumer</groupId>
	<artifactId>nacos-consumer</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>nacos-consumer</name>
	<description>Demo project for Spring Boot</description>

	<properties>
		<java.version>1.8</java.version>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
		<spring-boot.version>2.1.0.RELEASE</spring-boot.version>
	</properties>

	<dependencies>
		<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>
			<exclusions>
				<exclusion>
					<groupId>org.junit.vintage</groupId>
					<artifactId>junit-vintage-engine</artifactId>
				</exclusion>
			</exclusions>
		</dependency>

		<!--nacos依赖-->
		<dependency>
			<groupId>com.alibaba.cloud</groupId>
			<artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
			<version>2.0.1.RELEASE</version>
		</dependency>

		<!--openfeign依赖-->
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-openfeign</artifactId>
			<version>2.1.1.RELEASE</version>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-jdbc</artifactId>
		</dependency>
		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
		</dependency>
		<dependency>
			<groupId>org.projectlombok</groupId>
			<artifactId>lombok</artifactId>
			<version>1.16.10</version>
		</dependency>
		<dependency>
			<groupId>io.swagger</groupId>
			<artifactId>swagger-annotations</artifactId>
			<version>1.5.13</version>
		</dependency>
		<dependency>
			<groupId>com.baomidou</groupId>
			<artifactId>mybatis-plus-boot-starter</artifactId>
			<version>3.2.0</version>
		</dependency>


	</dependencies>

	<dependencyManagement>
		<dependencies>
			<dependency>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-dependencies</artifactId>
				<version>${spring-boot.version}</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>
		</dependencies>
	</dependencyManagement>

	<build>
		<plugins>
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-compiler-plugin</artifactId>
				<configuration>
					<source>1.8</source>
					<target>1.8</target>
					<encoding>UTF-8</encoding>
				</configuration>
			</plugin>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>

</project>

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2、application.yml配置

server:
  port: 8087
spring:
  application:
    name: nacos-consumer
  cloud:
    nacos:
      discovery:
        server-addr: 127.0.0.1:8848
  
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/study_cloud?serverTimezone=Asia/Shanghai&useUnicode=true&characterEncoding=utf-8&allowMultiQueries=true&useSSL=false
    username: root
    password: root
  main:
    allow-bean-definition-overriding: true

logging:
  level:
    root: info
    org.springframework: info
mybatis-plus:
  mapper-locations: classpath*:xml
  type-aliases-package: com.example.nacosprovider.entity

nacos-provider: 
  ribbon:
    NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RandomRule

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3、ConsumerController

@RestController
@Slf4j
public class ConsumerController {

	@Autowired
	private RestTemplate restTemplate;

	@ApiOperation("负载均衡")
	@GetMapping("/loadBalance")
	public String loadBalance() {
		//调用生产者微服务
		String forObject = restTemplate.getForObject("http://nacos-provider/provider/", String.class);
		return  "-------" + forObject;
	}

}