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package com.czxy.nacos.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 {
    @LoadBalanced   //负载均衡
    @Bean
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

通过服务名调用服务提供者

package com.czxy.nacos.controller;

import com.czxy.nacos.feign.TestFeign;
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.RestController;
import org.springframework.web.client.RestTemplate;

import javax.annotation.Resource;


@RestController
public class TestController {
    @Resource
    private RestTemplate restTemplate;

    @RequestMapping(value = "/echo/{str}", method = RequestMethod.GET)
    public String echo(@PathVariable String str) {
        return restTemplate.getForObject("http://service-provider/echo/" + str, String.class);
    }
}

整合WebClient

WebClient和RestTemplate

RestTemplate 是 spring 3.0 引入的，底层IO模型是阻塞IO模型 Http客户端。
WebClient 是 spring 5.0 引入的，作为非阻塞式Reactive Http客户端，用于取代RestTemplate。

响应式IO模型

SpringMVC或Struct等框架都是基于Servlet的，其底层IO模型是阻塞IO模型。
Spring社区为了解决SpringMVC的阻塞模型在高并发场景下的性能瓶颈，推出了Spring WebFlux，WebFlux底层实现是久经考验的Netty非阻塞IO通信框架。
其实WebClient处理单个HTTP请求的响应时长并不比RestTemplate更快，但是它处理==并发==的能力更强。所以响应式非阻塞IO模型的核心意义在于，提高了单位时间内有限资源下的服务请求的并发处理能力，而不是缩短了单个服务请求的响应时长。
总结：WebClient --> Spring WebFlux --> Netty

WebClient入门

添加 webflux 依赖

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

编写配置类

package com.czxy.config;

import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Component;
import org.springframework.web.reactive.function.client.WebClient;


@Component
public class WebClientConfig {

    @Bean
    @LoadBalanced
    public WebClient.Builder webClientBuilder() {
        return WebClient.builder();
    }
}

编写测试类

package com.czxy.controller;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.reactive.function.client.WebClient;
import reactor.core.publisher.Mono;

import javax.annotation.Resource;


@RestController
@RequestMapping("/client")
public class TestClientController {

    @Resource
    private WebClient.Builder webClientBuilder;

    @GetMapping("/echo/{str}")
    public Mono<String> echo(@PathVariable("str") String str) {
        return webClientBuilder.build()     // 创建WebClient实例
                .get()                      // 请求方式
                .uri("http://service-provider/echo/{1}", str) // 请求url
                .retrieve()                 // 获取响应结果
                .bodyToMono(String.class);  // 将结果转换为指定类型
    }

}

测试

http://localhost:8071/client/echo/123

API详解

请求方式

方法	描述	等效
build().get()	get请求	build().method(HttpMethod.GET)
build().post()	post请求	build().method(HttpMethod.POST)
build().put()	put请求	build().method(HttpMethod.PUT)
build().delete()	delete请求	build().method(HttpMethod.DELETE)

响应类型

类型	描述	方法
Mono	包含0个或1个元素	bodyToMono(String.class)
Flux	包含1个或多个元素	.bodyToFlux(String.class)

整合Feign

概述

RestTemplate和WebClient都是Spring自己封装的工具
Feign 是 Spring Cloud 的成员
Spring Cloud Alibaba 支持对Feign的调用

整合Feign

添加坐标

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

编写feign

package com.czxy.feign;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;


// @FeignClient(value = "服务名", path = "controller配置的路径" )
@FeignClient(value = "service-provider")
public interface EchoFeign {

    // 与 nacos-provider-2.1>EchoController声明的方法的完全一致
    @GetMapping("/echo/{string}")
    public String echo(@PathVariable String string);
}

编写测试类

package com.czxy.controller;

import com.czxy.feign.EchoFeign;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;


@RestController
@RequestMapping("/feign")
public class TestFeignController {
    @Resource
    private EchoFeign echoFeign;

    @GetMapping("/echo/{str}")
    public String echo(@PathVariable String str) {
        return echoFeign.echo(str);
    }
}

修改启动类

package com.czxy;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;


@SpringBootApplication
@EnableDiscoveryClient      //服务发现
@EnableFeignClients         //远程调用
public class TestNacosConsumerApplication {
    public static void main(String[] args) {
        SpringApplication.run(TestNacosConsumerApplication.class, args );
    }
}