Dubbo（十）之配置加载流程

阳光穿透心脏的1/2处 2022-10-25 13:00 199阅读 0赞

转载自  [Dubbo配置加载流程][Dubbo]

Dubbo 中的配置加载流程介绍

此篇文档主要讲在**应用启动阶段，Dubbo框架如何将所需要的配置采集起来**（包括应用配置、注册中心配置、服务配置等），以完成服务的暴露和引用流程。

根据驱动方式的不同（比如Spring或裸API编程）配置形式上肯定会有所差异，具体请参考[XML配置][XML]、[Annotation配置][Annotation]、[API配置][API]三篇文档。除了外围驱动方式上的差异，Dubbo的配置读取总体上遵循了以下几个原则：

1.  Dubbo 支持了多层级的配置，并按预定优先级自动实现配置间的覆盖，最终所有配置汇总到数据总线URL后驱动后续的服务暴露、引用等流程。
2.  ApplicationConfig、ServiceConfig、ReferenceConfig 可以被理解成配置来源的一种，是直接面向用户编程的配置采集方式。
3.  配置格式以 Properties 为主，在配置内容上遵循约定的 `path-based` 的命名[规范][Link 1]

## 配置来源 ##

首先，从Dubbo支持的配置来源说起，默认有四种配置来源：

*  JVM System Properties，-D 参数
 *  Externalized Configuration，外部化配置
 *  ServiceConfig、ReferenceConfig 等编程接口采集的配置
 *  本地配置文件 dubbo.properties

### 覆盖关系 ###

下图展示了配置覆盖关系的优先级，从上到下优先级依次降低：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21vYWt1bg_size_16_color_FFFFFF_t_70][]

点此查看[外部化配置详情][Link 2]

## 配置格式 ##

目前Dubbo支持的所有配置都是`.properties`格式的，包括`-D`、`Externalized Configuration`等，`.properties`中的所有配置项遵循一种`path-based`的配置格式：

# 应用级别
    dubbo.{config-type}[.{config-id}].{config-item}={config-item-value}
    # 服务级别
    dubbo.service.{interface-name}[.{method-name}].{config-item}={config-item-value}
    dubbo.reference.{interface-name}[.{method-name}].{config-item}={config-item-value}
    # 多配置项
    dubbo.{config-type}s.{config-id}.{config-item}={config-item-value}

应用级别

dubbo.application.name=demo-provider
    dubbo.registry.address=zookeeper://127.0.0.1:2181
    dubbo.protocol.port=-1

服务级别

dubbo.service.org.apache.dubbo.samples.api.DemoService.timeout=5000
    dubbo.reference.org.apache.dubbo.samples.api.DemoService.timeout=6000
    dubbo.reference.org.apache.dubbo.samples.api.DemoService.sayHello.timeout=7000

多配置项

dubbo.registries.unit1.address=zookeeper://127.0.0.1:2181
    dubbo.registries.unit2.address=zookeeper://127.0.0.1:2182
    
    dubbo.protocols.dubbo.name=dubbo
    dubbo.protocols.dubbo.port=20880
    dubbo.protocols.hessian.name=hessian
    dubbo.protocols.hessian.port=8089

扩展配置

dubbo.application.parameters.item1=value1
    dubbo.application.parameters.item2=value2
    dubbo.registry.parameters.item3=value3
    dubbo.reference.org.apache.dubbo.samples.api.DemoService.parameters.item4=value4

## 几种编程配置方式 ##

接下来，我们看一下选择不同的开发方式时，对应到 ServiceConfig、ReferenceConfig 等编程接口采集的配置的变化。

Spring XML

> 参见[示例][Link 3]

<dubbo:application name="demo-provider"/>
      <dubbo:config-center address="zookeeper://127.0.0.1:2181"/>
      
      <dubbo:registry address="zookeeper://127.0.0.1:2181" simplified="true"/>
      <dubbo:metadata-report address="redis://127.0.0.1:6379"/>
      <dubbo:protocol name="dubbo" port="20880"/>
      
      <bean id="demoService" class="org.apache.dubbo.samples.basic.impl.DemoServiceImpl"/>
      <dubbo:service interface="org.apache.dubbo.samples.basic.api.DemoService" ref="demoService"/>

Spring Annotation

> 参见[示例][Link 4]

// AnnotationService服务实现
      
      @Service
      public class AnnotationServiceImpl implements AnnotationService {
          @Override
          public String sayHello(String name) {
              System.out.println("async provider received: " + name);
              return "annotation: hello, " + name;
          }
      }

## dubbo.properties
      
      dubbo.application.name=annotation-provider
      dubbo.registry.address=zookeeper://127.0.0.1:2181
      dubbo.protocol.name=dubbo
      dubbo.protocol.port=20880

Spring Boot

> 参见[示例][Link 5]

## application.properties
      
      # Spring boot application
      spring.application.name=dubbo-externalized-configuration-provider-sample
      
      # Base packages to scan Dubbo Component: @com.alibaba.dubbo.config.annotation.Service
      dubbo.scan.base-packages=com.alibaba.boot.dubbo.demo.provider.service
      
      # Dubbo Application
      ## The default value of dubbo.application.name is ${spring.application.name}
      ## dubbo.application.name=${spring.application.name}
      
      # Dubbo Protocol
      dubbo.protocol.name=dubbo
      dubbo.protocol.port=12345
      
      ## Dubbo Registry
      dubbo.registry.address=N/A
      
      ## DemoService version
      demo.service.version=1.0.0

API

> 参考[示例][Link 6]

public static void main(String[] args) throws IOException {
        ServiceConfig<GreetingsService> service = new ServiceConfig<>();
        service.setApplication(new ApplicationConfig("first-dubbo-provider"));
        service.setRegistry(new RegistryConfig("multicast://224.5.6.7:1234"));
        service.setInterface(GreetingsService.class);
        service.setRef(new GreetingsServiceImpl());
        service.export();
        System.out.println("first-dubbo-provider is running.");
        System.in.read();
    }

[Dubbo]: https://dubbo.apache.org/zh/docs/v2.7/user/configuration/configuration-load-process/
[XML]: https://dubbo.apache.org/zh/docs/v2.7/user/configuration/xml
[Annotation]: https://dubbo.apache.org/zh/docs/v2.7/user/configuration/annotation
[API]: https://dubbo.apache.org/zh/docs/v2.7/user/configuration/api
[Link 1]: https://dubbo.apache.org/zh/docs/v2.7/user/configuration/configuration-load-process/#%E9%85%8D%E7%BD%AE%E6%A0%BC%E5%BC%8F
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21vYWt1bg_size_16_color_FFFFFF_t_70]: /images/20221024/4330e8aa84ef44508f5d9c4752c99a1f.png
[Link 2]: https://dubbo.apache.org/zh/docs/v2.7/user/configuration/config-center
[Link 3]: https://github.com/apache/dubbo-samples/tree/master/dubbo-samples-basic
[Link 4]: https://github.com/apache/dubbo-samples/tree/master/dubbo-samples-annotation
[Link 5]: https://github.com/apache/dubbo-spring-boot-project/tree/master/dubbo-spring-boot-samples
[Link 6]: https://github.com/apache/dubbo-samples/tree/master/dubbo-samples-api