Dubbo 2.7.8 整合Apollo配置中心，在指定外部配置的情况下，无法获取正确的Namespace，应用启动失败

[pengshaoxing]

• I have searched the issues of this repository and believe that this is not a duplicate.
• I have checked the FAQ of this repository and believe that this is not a duplicate.

Environment

• Dubbo version: 2.7.8
• Operating System version: WINDOWS 10 20H1
• Java version: Java 1.8

Steps to reproduce this issue

1. 配置文件中指定apollo配置中心的相关值。

dubbo:
  config-center:
    address: apollo://t.ppssxx.com:8080
    # 配置中心的配置覆盖本地配置
    highest-priority: true
    namespace: TEST1.dubbo
    config-file: TEST1.dubbo.properties
    group: TEST1.dubbo
    app-config-file: TEST1.dubbo.properties

2. 启动应用，拉取配置
3. 应用启动失败

Pls. provide [GitHub address] to reproduce this issue.

Expected Result

What do you expected from the above steps？

应该正确获取到配置文件中指定的Namespace值,在本场景中为TEST1.dubbo

Actual Result

未能正确获取，而是变成了默认的dubbo
What actually happens?

If there is an exception, please attach the exception trace:

2020-08-16 23:34:37.645 ERROR 3752 --- [           main] o.s.boot.SpringApplication               : Application run failed

java.lang.IllegalStateException: Failed to connect to config center, the config center is Apollo, the address is: http://xxx:8080
	at org.apache.dubbo.configcenter.support.apollo.ApolloDynamicConfiguration.<init>(ApolloDynamicConfiguration.java:109) ~[dubbo-2.7.8.jar:2.7.8]
	at org.apache.dubbo.configcenter.support.apollo.ApolloDynamicConfigurationFactory.createDynamicConfiguration(ApolloDynamicConfigurationFactory.java:29) ~[dubbo-2.7.8.jar:2.7.8]
	at org.apache.dubbo.common.config.configcenter.AbstractDynamicConfigurationFactory.lambda$getDynamicConfiguration$0(AbstractDynamicConfigurationFactory.java:39) ~[dubbo-2.7.8.jar:2.7.8]
	at java.base/java.util.concurrent.ConcurrentHashMap.computeIfAbsent(ConcurrentHashMap.java:1708) ~[na:na]
	at org.apache.dubbo.common.config.configcenter.AbstractDynamicConfigurationFactory.getDynamicConfiguration(AbstractDynamicConfigurationFactory.java:39) ~[dubbo-2.7.8.jar:2.7.8]
	at org.apache.dubbo.common.config.configcenter.DynamicConfiguration.getDynamicConfiguration(DynamicConfiguration.java:224) ~[dubbo-2.7.8.jar:2.7.8]
	at org.apache.dubbo.config.bootstrap.DubboBootstrap.prepareEnvironment(DubboBootstrap.java:1034) ~[dubbo-2.7.8.jar:2.7.8]
	at org.apache.dubbo.config.bootstrap.DubboBootstrap.startConfigCenter(DubboBootstrap.java:623) ~[dubbo-2.7.8.jar:2.7.8]
	at org.apache.dubbo.config.bootstrap.DubboBootstrap.initialize(DubboBootstrap.java:521) ~[dubbo-2.7.8.jar:2.7.8]
	at org.apache.dubbo.config.bootstrap.DubboBootstrap.start(DubboBootstrap.java:896) ~[dubbo-2.7.8.jar:2.7.8]
	at org.apache.dubbo.config.spring.context.DubboBootstrapApplicationListener.onContextRefreshedEvent(DubboBootstrapApplicationListener.java:59) ~[dubbo-2.7.8.jar:2.7.8]
	at org.apache.dubbo.config.spring.context.DubboBootstrapApplicationListener.onApplicationContextEvent(DubboBootstrapApplicationListener.java:52) ~[dubbo-2.7.8.jar:2.7.8]
	at org.apache.dubbo.config.spring.context.OneTimeExecutionApplicationContextEventListener.onApplicationEvent(OneTimeExecutionApplicationContextEventListener.java:40) ~[dubbo-2.7.8.jar:2.7.8]
	at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:402) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:359) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:896) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:552) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:742) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:389) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:311) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1213) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1202) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at com.sf.dubbo.bootstrap.providerApplication.main(providerApplication.java:28) ~[classes/:na]

查看源码和调式发现：

dubbo/dubbo-configcenter/dubbo-configcenter-apollo/src/main/java/org/apache/dubbo/configcenter/support/apollo/ApolloDynamicConfiguration.java

Lines 99 to 102 in 0be2a1b

	String namespace = url.getParameter(CONFIG_NAMESPACE_KEY, DEFAULT_GROUP);
	String apolloNamespace = StringUtils.isEmpty(namespace) ? url.getParameter(GROUP_KEY, DEFAULT_GROUP) : namespace;
	dubboConfig = ConfigService.getConfig(apolloNamespace);
	dubboConfigFile = ConfigService.getConfigFile(apolloNamespace, ConfigFileFormat.Properties);

这里截取的ParameterKey 不对，这里获取的是config.namespace，而在url内部的Parameter实际为namesapce，导致获取为空，由于给了默认值下面的语句判空也没有发挥任何作用，appConfigFile的值也未能正确获取到。

[furaul]

在2.7.x较早的版本中，ConfigCenterConfig中的namespace等属性，都有一个@parameter注解，在ConfigCenterConfig实例转换成URL的时候，构建Url实体的parameter时，key使用的是@parameter里面的key属性。读取逻辑见org.apache.dubbo.common.constants.CommonConstants.CONFIG_NAMESPACE_KEY;

在2.7.x近期的版本中，ConfigCenterConfig中的namespace等属性去掉了@parameter注解，构建Url的时候，key使用的是属性名本身。

但是在Apollo、etcd等配置中心的实现类，比如ApolloDynamicConfiguration中，读取namespace的key使用的还是org.apache.dubbo.common.constants.CommonConstants.CONFIG_NAMESPACE_KEY，导致读取失败。

详情修改见 #6717

[AlbumenJ]

close #6606 via #6717