@Override
    protected String getServiceConfig(final String key, final Consumer<String> updateHandler, final Consumer<String> deleteHandler) {
        if (watchCache.containsKey(key)) {
            return null;
        }
        try {
            final ConfigFileChangeListener listener = event -> {
                try {
                    if (event.getChangeType().equals(ChangeType.DELETED) || StringUtils.isBlank(event.getNewValue())) {
                        Optional.ofNullable(deleteHandler).ifPresent(deleteHandler2 -> deleteHandler2.accept(key));
                    } else {
                        if (event.getNewValue().equals(event.getOldValue())) {
                            return;
                        }
                        updateHandler.accept(event.getNewValue());
                    }
                } catch (Exception e) {
                    LOG.error("Polaris sync listener receiveConfigInfo error", e);
                }
            };
            final ConfigFile configFile = configFileService.getConfigFile(polarisConfig.getNamespace(), polarisConfig.getFileGroup(), key);
            configFile.addChangeListener(listener);
            watchCache.put(key, listener);
            return configFile.hasContent() ? configFile.getContent() : null;
        } catch (Exception e) {
            throw new ShenyuException(e);
        }
    }
The type Polaris sync data service.
shenyu-sync-data-center/shenyu-sync-data-polaris/src/main/java/org/apache/shenyu/sync/data/polaris/PolarisSyncDataService.java