修改异常抛出机制，当读取配置失败，不能影响服务注册发现功能

discovery-plugin-config-center/src/main/java/com/nepxion/discovery/plugin/configcenter/ConfigParser.java

@@ -9,7 +9,6 @@ package com.nepxion.discovery.plugin.configcenter;
  * @version 1.0
  */
 
-import java.io.IOException;
 import java.io.InputStream;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -21,7 +20,6 @@ import java.util.concurrent.locks.ReentrantReadWriteLock;
 import org.apache.commons.io.IOUtils;
 import org.apache.commons.lang3.StringUtils;
 import org.dom4j.Attribute;
-import org.dom4j.DocumentException;
 import org.dom4j.Element;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -55,10 +53,10 @@ public class ConfigParser extends Dom4JParser {
             String text = IOUtils.toString(inputStream, PluginConstant.ENCODING_UTF_8);
 
             super.parse(text);
-        } catch (IOException e) {
-            throw new PluginException(e);
-        } catch (DocumentException e) {
-            throw new PluginException(e);
+        } catch (NullPointerException e) {
+            LOG.warn("No input stream is retrieved");
+        } catch (Exception e) {
+            LOG.error("Parse rule xml failed", e);
         } finally {
             if (inputStream != null) {
                 IOUtils.closeQuietly(inputStream);