Conflict with Spring cloud SpringApplication run

Conflict with Spring cloud SpringApplication run. spring cloud because BootstrapApplicationListener.Causes Spring Application to execute many times.
and call **FluentLogger** stop. close sender, with sender is null.
then call `log(String tag, Map data, long timestamp) ` function Throw out NullPointerException？
in **FluentLoggerFactory** 58 line add this code?
```
public synchronized FluentLogger getLogger(String tagPrefix, String host, int port, int timeout, int bufferCapacity,
Reconnector reconnector) {
String key = String.format("%s_%s_%d_%d_%d", new Object[] { tagPrefix, host, port, timeout, bufferCapacity });

for (Map.Entry entry : loggers.entrySet()) {
if (entry.getValue().equals(key)) {
FluentLogger found = entry.getKey();
if(found != null) {
if(found.getSender() == null){
found.setSender(getNewSender(host, port, timeout, bufferCapacity, reconnector));
}
return found;
}
break;
}
}

FluentLogger logger = new FluentLogger(tagPrefix, getNewSender(host, port, timeout, bufferCapacity, reconnector));
loggers.put(logger, key);
return logger;
}

private Sender getNewSender( String host, int port, int timeout, int bufferCapacity, Reconnector reconnector){
Sender sender = null;
Properties props = System.getProperties();
if (!props.containsKey(Config.FLUENT_SENDER_CLASS)) {
// create default sender object
sender = new RawSocketSender(host, port, timeout, bufferCapacity, reconnector);
} else {
String senderClassName = props.getProperty(Config.FLUENT_SENDER_CLASS);
try {
sender = createSenderInstance(senderClassName, new Object[] { host, port, timeout, bufferCapacity });
} catch (Exception e) {
throw new RuntimeException(e);
}
}
return sender;
}
```

Start with FluentLoggerFactory around line 58 and inspect how FluentLogger sender lifecycle interacts with SpringApplication and BootstrapApplicationListener. Reproduce the NullPointerException in log(String tag, Map data, long timestamp), then add coverage for the null-sender case; done means repeated application startup no longer causes the failure.

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