From 13c5304139ab21017eda66e0c73540df19f5945f Mon Sep 17 00:00:00 2001
From: bunny <1319900154@qq.com>
Date: Mon, 26 May 2025 13:56:57 +0800
Subject: [PATCH] =?UTF-8?q?:sparkles:=20=E8=B4=9F=E8=BD=BD=E5=9D=87?=
 =?UTF-8?q?=E8=A1=A1=E6=B3=A8=E8=A7=A3=E8=B0=83=E7=94=A8?=
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---
 cloud-demo/ReadMe.md                          | 85 ++++++++++++++++++-
 .../service/config/OrderServiceConfig.java    |  2 +
 .../service/impl/OrderServiceImpl.java        | 17 +++-
 3 files changed, 102 insertions(+), 2 deletions(-)

diff --git a/cloud-demo/ReadMe.md b/cloud-demo/ReadMe.md
index 1af76a5..bbb6c3c 100644
--- a/cloud-demo/ReadMe.md
+++ b/cloud-demo/ReadMe.md
@@ -304,7 +304,18 @@ public ClientHttpRequestFactory getRequestFactory() {
 }
 ```
 
-**实现远程调用**
+#### 实现远程调用
+
+##### 普通方式调用
+
+注册`RestTemplate`
+
+```java
+@Bean
+public RestTemplate restTemplate() {
+    return new RestTemplate();
+}
+```
 
 如果我们的服务启动了多个，在下面代码中即使一个服务宕机也可以做到远程调用。
 
@@ -322,3 +333,75 @@ private Product getProductFromRemote(Long productId) {
     return restTemplate.getForObject(url, Product.class);
 }
 ```
+
+##### 负载均衡调用
+
+注册`RestTemplate`
+
+```java
+@Bean
+public RestTemplate restTemplate() {
+    return new RestTemplate();
+}
+```
+
+使用负载均衡`LoadBalancerClient`，通过负载均衡算法动态调用远程服务。
+
+```java
+/**
+ * 远程调用商品模块 --- 负载均衡
+ *
+ * @param productId 商品id
+ * @return 商品对象
+ */
+private Product getProductFromRemoteWithLoadBalancer(Long productId) {
+    // 1. 获取商品服务所有及其的 IP+port
+    ServiceInstance instance = loadBalancerClient.choose("service-product");
+
+    // 远程URL
+    String url = "http://" + instance.getHost() + ":" + instance.getPort() + "/api/product/" + productId;
+
+    // 2. 远程发送请求
+    log.info("负载均衡远程调用：{}", url);
+    return restTemplate.getForObject(url, Product.class);
+}
+```
+
+##### 负载均衡注解调用
+
+> [!TIP]
+>
+> 如果远程注册中心宕机是否可以调用？
+>
+> 调用过：远程调用不在依赖注册中心，可以通过。
+>
+> 没调用过：第一次发起远程调用；不能通过。
+
+在`RestTemplate`上加上`@LoadBalanced`注解使用负载均衡。
+
+```java
+@Bean
+@LoadBalanced
+public RestTemplate restTemplate() {
+    return new RestTemplate();
+}
+```
+
+在实际的调用中并不需要再显式调用，将URL替换成服务名称即可。
+
+```java
+/**
+ * 远程调用商品模块 --- 负载均衡注解调用
+ *
+ * @param productId 商品id
+ * @return 商品对象
+ */
+private Product getProductFromRemoteWithLoadBalancerAnnotation(Long productId) {
+    // 远程URL，实现动态替换
+    String url = "http://service-product/api/product/" + productId;
+
+    // 远程发送请求
+    log.info("负载均衡注解调用：{}", url);
+    return restTemplate.getForObject(url, Product.class);
+}
+```
diff --git a/cloud-demo/services/service-order/src/main/java/cn/bunny/service/config/OrderServiceConfig.java b/cloud-demo/services/service-order/src/main/java/cn/bunny/service/config/OrderServiceConfig.java
index a64fe66..c3db747 100644
--- a/cloud-demo/services/service-order/src/main/java/cn/bunny/service/config/OrderServiceConfig.java
+++ b/cloud-demo/services/service-order/src/main/java/cn/bunny/service/config/OrderServiceConfig.java
@@ -1,5 +1,6 @@
 package cn.bunny.service.config;
 
+import org.springframework.cloud.client.loadbalancer.LoadBalanced;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.web.client.RestTemplate;
@@ -8,6 +9,7 @@ import org.springframework.web.client.RestTemplate;
 public class OrderServiceConfig {
 
     @Bean
+    @LoadBalanced
     public RestTemplate restTemplate() {
         return new RestTemplate();
     }
diff --git a/cloud-demo/services/service-order/src/main/java/cn/bunny/service/service/impl/OrderServiceImpl.java b/cloud-demo/services/service-order/src/main/java/cn/bunny/service/service/impl/OrderServiceImpl.java
index 0e4e748..2fef61d 100644
--- a/cloud-demo/services/service-order/src/main/java/cn/bunny/service/service/impl/OrderServiceImpl.java
+++ b/cloud-demo/services/service-order/src/main/java/cn/bunny/service/service/impl/OrderServiceImpl.java
@@ -32,7 +32,7 @@ public class OrderServiceImpl implements OrderService {
      */
     @Override
     public Order createOrder(Long productId, Long userId) {
-        Product product = getProductFromRemoteWithLoadBalancer(productId);
+        Product product = getProductFromRemoteWithLoadBalancerAnnotation(productId);
 
         Order order = new Order();
         order.setId(1L);
@@ -83,4 +83,19 @@ public class OrderServiceImpl implements OrderService {
         log.info("负载均衡远程调用：{}", url);
         return restTemplate.getForObject(url, Product.class);
     }
+
+    /**
+     * 远程调用商品模块 --- 负载均衡注解调用
+     *
+     * @param productId 商品id
+     * @return 商品对象
+     */
+    private Product getProductFromRemoteWithLoadBalancerAnnotation(Long productId) {
+        // 远程URL，实现动态替换
+        String url = "http://service-product/api/product/" + productId;
+
+        // 远程发送请求
+        log.info("负载均衡注解调用：{}", url);
+        return restTemplate.getForObject(url, Product.class);
+    }
 }