Dubbo服务发现
Dubbo 提供的是一种 Client-Based 的服务发现机制，依赖第三方注册中心组件来协调服务发现过程，支持常用的注册中心如 Nacos、Consul、Zookeeper 等。
以下是 Dubbo 服务发现机制的基本工作原理图：
服务发现包含提供者、消费者和注册中心三个参与角色，其中，Dubbo 提供者实例注册 URL 地址到注册中心，注册中心负责对数据进行聚合，Dubbo 消费者从注册中心读取地址列表并订阅变更，每当地址列表发生变化，注册中心将最新的列表通知到所有订阅的消费者实例。
Dubbo与Nacos整合
前置条件
● 当Dubbo使用3.0.0及以上版本时，需要使用Nacos 2.0.0及以上版本。
● 注意：目前最新版本Dubbo 3.1.8不支持Spring Boot 3，因此开发环境必须基于Spring Boot 2.x + JDK17/8，对应的Spring Cloud与Spring Cloud Alibaba也要调整为2021.x
<properties>
<java.version>17</java.version>
<spring-cloud.version>2021.0.3</spring-cloud.version>
<spring-cloud-alibaba.version>2021.0.4.0</spring-cloud-alibaba.version>
</properties>
生产者服务provider-service-dubbo
<dependency>
<groupId>org.apache.dubbo</groupId>
<artifactId>dubbo-spring-boot-starter</artifactId>
<version>3.1.8</version>
</dependency>
配置文件application.yaml
server:
port: 8001
spring:
application:
name: provider-service
cloud:
nacos:
server-addr: 192.168.31.231:8848
username: nacos
password: nacos
dubbo:
application:
name: provider-service-dubbo
registry:
address: nacos://192.168.31.231:8848
username: nacos
password: nacos
protocol:
name: dubbo
port: 20880
logging:
level:
root: info
应用入口增加两个注解，启用Dubbo
● @EnableDubbo
@EnableDubbo是一个注解，用于启用Dubbo的自动配置，将Dubbo服务注册到注册中心。它可以放置在Spring Boot应用程序的主类上。通过使用@EnableDubbo注解，可以避免手动配置Dubbo服务的繁琐工作，只需添加相应的注解和配置参数即可自动配置Dubbo。
● @DubboComponentScan
@DubboComponentScan是一个注解，用于扫描Dubbo服务的实现类。它可以放置在Spring Boot应用程序的主类上。通过使用@DubboComponentScan注解，可以自动扫描指定包及其子包中的Dubbo服务实现类，将它们注册为Dubbo服务。这样，Dubbo框架就能够自动发现和管理Dubbo服务，方便使用和维护。
package com.itlaoqi.providerservicedubbo;
import org.apache.dubbo.config.spring.context.annotation.DubboComponentScan;
import org.apache.dubbo.config.spring.context.annotation.EnableDubbo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
@EnableDubbo
@DubboComponentScan
public class ProviderServiceDubboApplication {
public static void main(String[] args) {
SpringApplication.run(ProviderServiceDubboApplication.class, args);
}
}
实现业务接口
接口
package com.itlaoqi.providerservicedubbo.dubbo;
import com.itlaoqi.providerservicedubbo.entity.User;
import org.springframework.http.ResponseEntity;
import java.util.List;
import java.util.Map;
public interface ProviderService {
public Map hello();
public User createUser(String uid, String username, String password, String nickname);
public ResponseEntity<List<User>> query(int page, int rows);
}
实现
@DubboService是一个注解，用于标注Dubbo服务的实现类。在Dubbo框架中，服务提供者需要将服务注册到注册中心，以便服务消费者能够发现和调用服务。@DubboService注解可以将标注的服务实现类注册为Dubbo服务，使其能够被Dubbo框架自动管理和发布。
package com.itlaoqi.providerservicedubbo.dubbo.impl;
import com.itlaoqi.providerservicedubbo.dubbo.ProviderService;
import com.itlaoqi.providerservicedubbo.dto.User;
import org.apache.dubbo.config.annotation.DubboService;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
@DubboService
public class ProviderServiceImpl implements ProviderService {
public Map hello() {
Map result = new HashMap();
result.put("code", "0");
result.put("message", "hello world~");
return result;
}
public User createUser(String uid, String username , String password , String nickname) {
return new User(uid,username,password,nickname);
}
public ResponseEntity<List<User>> query(int page, int rows) {
List<User> users = new ArrayList<>();
for (int i = rows * (page - 1); i < rows * page; i++) {
String uid = "uid:" + i;
String username = "username-" + i;
String password = "password-" + i;
String nickname = "nickname-" + i;
User user = new User(uid, username, password, nickname);
users.add(user);
}
return new ResponseEntity<>(users, HttpStatus.OK);
}
}
注意，需要依赖的DTO对象，必须实现序列化接口Serializable
package com.itlaoqi.providerservicedubbo.dto;
import lombok.AllArgsConstructor;
import lombok.Data;
import java.io.Serializable;
@Data
@AllArgsConstructor
public class User implements Serializable {
private String uid;
private String username;
private String password;
private String nickname;
}
启动时要万分注意，JDK17与Dubbo 3.1.8有兼容问题，需要在启动项增加，官方说3.2版本会修正这个问题
--add-opens java.base/java.lang=ALL-UNNAMED
消费者服务consumer-service-dubbo
<dependency>
<groupId>org.apache.dubbo</groupId>
<artifactId>dubbo-spring-boot-starter</artifactId>
<version>3.1.8</version>
</dependency>
配置消费者接口
server:
port: 8002
spring:
application:
name: consumer-service
cloud:
nacos:
server-addr: 192.168.31.231:8848
username: nacos
password: nacos
dubbo:
application:
name: consumer-service-dubbo
registry:
address: nacos://192.168.31.231:8848
username: nacos
password: nacos
logging:
level:
root: info
启用Dubbo
package com.itlaoqi.consumerservicedubbo;
import org.apache.dubbo.config.spring.context.annotation.EnableDubbo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
@EnableDubbo
public class ConsumerServiceDubboApplication {
public static void main(String[] args) {
SpringApplication.run(ConsumerServiceDubboApplication.class, args);
}
}
将服务端接口与依赖的类加载到本地
● 复制源代码
● Maven依赖
注意包名是com.itlaoqi.providerservicedubbo.dubbo
package com.itlaoqi.providerservicedubbo.dubbo;
import com.itlaoqi.providerservicedubbo.dto.User;
import java.util.List;
import java.util.Map;
public interface ProviderService {
public Map hello();
public User createUser(String uid, String username, String password, String nickname);
public List<User> query(int page, int rows);
}
package com.itlaoqi.providerservicedubbo.dto;
import lombok.AllArgsConstructor;
import lombok.Data;
import java.io.Serializable;
@Data
@AllArgsConstructor
public class User implements Serializable {
private String uid;
private String username;
private String password;
private String nickname;
}
依赖并远程访问
● @DubboReference
通过在 Spring 容器中标记 @DubboReference 注解，可以让 Dubbo 自动为该属性注入一个代理对象，该对象可以调用远程 Dubbo 服务的方法，使得在使用 Dubbo 服务时可以像调用本地服务一样方便。
package com.itlaoqi.consumerservicedubbo.controller;
import com.itlaoqi.providerservicedubbo.dubbo.ProviderService;
import com.itlaoqi.providerservicedubbo.dto.User;
import org.apache.dubbo.config.annotation.DubboReference;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.List;
@RestController
public class ConsumerController {
@DubboReference
private ProviderService providerService;
@GetMapping("/list")
public List<User> list(int page, int rows) {
return providerService.query(page, rows);
}
}
执行结果
###
GET http://localhost:8002/list?page=2&rows=10
[
{
"uid": "uid:10",
"username": "username-10",
"password": "password-10",
"nickname": "nickname-10"
},
{
"uid": "uid:11",
"username": "username-11",
"password": "password-11",
"nickname": "nickname-11"
},
{
"uid": "uid:12",
"username": "username-12",
"password": "password-12",
"nickname": "nickname-12"
},
{
"uid": "uid:13",
"username": "username-13",
"password": "password-13",
"nickname": "nickname-13"
},
{
"uid": "uid:14",
"username": "username-14",
"password": "password-14",
"nickname": "nickname-14"
},
{
"uid": "uid:15",
"username": "username-15",
"password": "password-15",
"nickname": "nickname-15"
},
{
"uid": "uid:16",
"username": "username-16",
"password": "password-16",
"nickname": "nickname-16"
},
{
"uid": "uid:17",
"username": "username-17",
"password": "password-17",
"nickname": "nickname-17"
},
{
"uid": "uid:18",
"username": "username-18",
"password": "password-18",
"nickname": "nickname-18"
},
{
"uid": "uid:19",
"username": "username-19",
"password": "password-19",
"nickname": "nickname-19"
}
]
启动时要万分注意，JDK17与Dubbo 3.1.8有兼容问题，需要在启动项增加，官方说3.2版本会修正这个问题
--add-opens java.base/java.lang=ALL-UNNAMED
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