- [x] I have searched the [issues](https://github.com/apache/incubator-dubbo/issues) of this repository and believe that this is not a duplicate.
- [x] I have checked the [FAQ](https://github.com/apache/incubator-dubbo/blob/master/FAQ.md) of this repository and believe that this is not a duplicate.

### Environment

* Dubbo version: xxx
* Operating System version: xxx
* Java version: xxx

### Steps to reproduce this issue

1. xxx
2. xxx
3. xxx

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

### Expected Result

What do you expected from the above steps？

### Actual Result

What actually happens?

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

```
Just put your stack trace here!
```

import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.text.SimpleDateFormat;
import java.util.Date;
/**
 * LogTelnetHandler
 */
@Activate
@Help(parameter = "level", summary = "Change log level or show log ", detail = "Change log level or show log")
public class LogTelnetHandler implements TelnetHandler {
    public static final String SERVICE_KEY = "telnet.log";
    @Override
    public String telnet(Channel channel, String message) {
        long size = 0;
        File file = LoggerFactory.getFile();
        StringBuffer buf = new StringBuffer();
        if (message == null || message.trim().length() == 0) {
            buf.append("EXAMPLE: log error / log 100");
        } else {
            String str[] = message.split(" ");
            if (!StringUtils.isInteger(str[0])) {
                LoggerFactory.setLevel(Level.valueOf(message.toUpperCase()));
            } else {
                int showLogLength = Integer.parseInt(str[0]);
                if (file != null && file.exists()) {
                    try {
                        FileInputStream fis = new FileInputStream(file);
                        FileChannel filechannel = fis.getChannel();
                        size = filechannel.size();
                        ByteBuffer bb;