LoadBalancer 替换 Ribbon

<!-- LoadBalancer 必须引入 springcloud -->
<!-- 父pom引入springcloud 版本管理 -->  https://spring.io/projects/spring-cloud/  官网查看 boot 对应的 cloud 的版本
<dependencyManagement>
    <dependency>    
        <groupId>org.springframework.cloud</groupId>    
        <artifactId>spring-cloud-dependencies</artifactId>    
        <version>${spring-cloud.version}</version>    
        <type>pom</type>    
        <scope>import</scope>
    </dependency>
<dependencyManagement>

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

<!-- 提供了RestTemplate支持 -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

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