MetadataChangeListener (Apache Dubbo 2.7.16 API)

```
public interface MetadataChangeListener
```

方法概要

所有方法实例方法抽象方法默认方法
修饰符和类型	方法	说明
`default String`	`echo(String msg)`	Echo test Used to check consumer still online
`void`	`onEvent(String metadata)`	Call when metadata in provider side update

- 方法详细资料
  - onEvent
```
void onEvent(String metadata)
```
    Call when metadata in provider side update
    Used to notify consumer to update metadata of ServiceInstance
    
    参数:
    
    metadata - latest metadata
  - echo
```
default String echo(String msg)
```
    Echo test Used to check consumer still online