SpringCloud-three ways to use RestTemplate

Three ways to access services

1. The URL is dead, use new RestTemplate () to access the url to get the message. (This method is not applicable when the service has multiple nodes and multiple addresses)
2. Use loadBlancerClient to get the url, and then use new RestTemplate () to access the url to get the message. (Too cumbersome)
3. Annotate restTemplate with @LoadBlanced, then restTemplate can be accessed using the application name.

# product.yml

spring:
  application:
    name: product
  datasource:
    driver-class-name: com.mysql.jdbc.Driver
    username: root
    password: 123456
    url: jdbc:mysql://127.0.0.1:3306/SpringCloud_Sell?characterEncoding=utf-8&useSSL=false
  jpa:
    show-sql: true
eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka/

package com.imooc.product.controller;

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

@RestController
public class ServerController {

    @GetMapping("/msg")
    public String msg() {
        return "this is product' msg";
    }
}

package com.imooc.order.controller;

import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@RestController
@Slf4j
public class ClientController {

//    @Autowired
//    private LoadBalancerClient loadBalancerClient;

    @Autowired
    private RestTemplate restTemplate;

    @GetMapping("/getProductMsg")
    public String getProductMsg() {
        //1.第一种方式(直接使用restTemplate, url写死)
//        RestTemplate restTemplate = new RestTemplate();
//        String response = restTemplate.getForObject("http://localhost:8080/msg", String.class);

        //2. 第二种方式(利用loadBalancerClient通过应用名获取url, 然后再使用restTemplate)
//        RestTemplate restTemplate = new RestTemplate();
//        ServiceInstance serviceInstance = loadBalancerClient.choose("PRODUCT");
//        String url = String.format("http://%s:%s", serviceInstance.getHost(), serviceInstance.getPort()) + "/msg";
//        String response = restTemplate.getForObject(url, String.class);

        //3. 第三种方式(利用@LoadBalanced, 可在restTemplate里使用应用名字)
        String response = restTemplate.getForObject("http://PRODUCT/msg", String.class);

        log.info("response={}", response);
        return response;
    }
}

// 第三种情况

package com.imooc.order.config;

import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Component;
import org.springframework.web.client.RestTemplate;

@Component
public class RestTemplateConfig {

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