文档

配置加载流程

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Annotation配置API配置三篇文档。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

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:

覆盖关系

点此查看外部化配置详情

配置格式

目前Dubbo支持的所有配置都是.properties格式的,包括-DExternalized 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

  <!-- dubbo-provier.xml -->
  
  <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"/>
  • Annotation

参见示例

  // 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

  ## 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

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();
}

参考示例