Apollo客户端

一、使用

@EnableApolloConfig注解在启动类

@Bean注入bean

@SpringBootApplication
@Configuration
@EnableApolloConfig
class Demo2Application {

    public static void main(String[] args) {
        SpringApplication.run(Demo2Application.class, args);

    }

    @Bean
    public TestJavaConfigBean javaConfigBean() {
        return new TestJavaConfigBean();
    }
}

@ApolloConfig将 Apollo Config 对象注入

@ApolloConfigChangeListener将被注解的方法，向指定的 Apollo Config 发起配置变更监听
对应的处理器--ApolloAnnotationProcessor

@Slf4j
public class TestJavaConfigBean {
    @ApolloConfig("application")
    private Config config;

    //config change listener for namespace application
    @ApolloConfigChangeListener("application")
    private void anotherOnChange(ConfigChangeEvent changeEvent) {

        ConfigChange change = changeEvent.getChange("test");
        System.out.println(String.format("Found change - key: %s, oldValue: %s,"
                + " newValue: %s, changeType: %s", change.getPropertyName(), change.getOldValue(), change.getNewValue(), change.getChangeType()));
    }
}

@ApolloJsonValue将一个 Item 配置项，解析成对应类型的对象

二、原理

ApolloAnnotationProcessor

com.ctrip.framework.apollo.spring.annotation.ApolloAnnotationProcessor ，实现 BeanFactoryAware 接口，继承 ApolloProcessor 抽象类，处理 @ApolloConfig 和 @ApolloConfigChangeListener 注解处理器的初始化。

2.1 processField

@Override
protected void processField(Object bean, String beanName, Field field) {
    ApolloConfig annotation = AnnotationUtils.getAnnotation(field, ApolloConfig.class);
    if (annotation == null) {
        return;
    }

    Preconditions.checkArgument(Config.class.isAssignableFrom(field.getType()), "Invalid type: %s for field: %s, should be Config", field.getType(), field);

    // 创建 Config 对象
    String namespace = annotation.value();
    Config config = ConfigService.getConfig(namespace);

    // 设置 Config 对象，到对应的 Field
    ReflectionUtils.makeAccessible(field);
    ReflectionUtils.setField(field, bean, config);
}

• 处理 @ApolloConfig 注解，创建( 获得 )对应的 Config 对象，设置到注解的 Field 中。

2.2 processMethod

@Override
protected void processMethod(final Object bean, String beanName, final Method method) {
    ApolloConfigChangeListener annotation = AnnotationUtils.findAnnotation(method, ApolloConfigChangeListener.class);
    if (annotation == null) {
        return;
    }
    Class[] parameterTypes = method.getParameterTypes();
    Preconditions.checkArgument(parameterTypes.length == 1, "Invalid number of parameters: %s for method: %s, should be 1", parameterTypes.length, method);
    Preconditions.checkArgument(ConfigChangeEvent.class.isAssignableFrom(parameterTypes[0]), "Invalid parameter type: %s for method: %s, should be ConfigChangeEvent", parameterTypes[0], method);

    // 创建 ConfigChangeListener 监听器。该监听器会调用被注解的方法。
    ReflectionUtils.makeAccessible(method);
    ConfigChangeListener configChangeListener = new ConfigChangeListener() {
        @Override
        public void onChange(ConfigChangeEvent changeEvent) {
            ReflectionUtils.invokeMethod(method, bean, changeEvent);
        }
    };

    // 向指定 Namespace 的 Config 对象们，注册该监听器
    String[] namespaces = annotation.value();
    for (String namespace : namespaces) {
        Config config = ConfigService.getConfig(namespace);
        config.addChangeListener(configChangeListener);
    }
}

• 处理 @ApolloConfigChangeListener 注解，创建回调注解方法的 ConfigChangeListener 对象，并向指定 Namespace 们的 Config 对象们，注册该监听器。