diff --git a/webmagic-extension/src/main/java/us/codecraft/webmagic/monitor/SpiderMonitor.java b/webmagic-extension/src/main/java/us/codecraft/webmagic/monitor/SpiderMonitor.java
index b213dda9..50dbcaf1 100644
--- a/webmagic-extension/src/main/java/us/codecraft/webmagic/monitor/SpiderMonitor.java
+++ b/webmagic-extension/src/main/java/us/codecraft/webmagic/monitor/SpiderMonitor.java
@@ -1,21 +1,25 @@
 package us.codecraft.webmagic.monitor;
 
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-import us.codecraft.webmagic.Request;
-import us.codecraft.webmagic.Spider;
-import us.codecraft.webmagic.SpiderListener;
-import us.codecraft.webmagic.utils.Experimental;
-import us.codecraft.webmagic.utils.UrlUtils;
-
-import javax.management.*;
 import java.lang.management.ManagementFactory;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
-import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 
+import javax.management.InstanceAlreadyExistsException;
+import javax.management.JMException;
+import javax.management.MBeanRegistrationException;
+import javax.management.MBeanServer;
+import javax.management.MalformedObjectNameException;
+import javax.management.NotCompliantMBeanException;
+import javax.management.ObjectName;
+
+import us.codecraft.webmagic.Request;
+import us.codecraft.webmagic.Spider;
+import us.codecraft.webmagic.SpiderListener;
+import us.codecraft.webmagic.utils.Experimental;
+import us.codecraft.webmagic.utils.UrlUtils;
+
 /**
  * @author code4crafer@gmail.com
  * @since 0.5.0
@@ -23,17 +27,13 @@ import java.util.concurrent.atomic.AtomicInteger;
 @Experimental
 public class SpiderMonitor {
 
-    private static SpiderMonitor INSTANCE = new SpiderMonitor();
-
-    private AtomicBoolean started = new AtomicBoolean(false);
-
-    private Logger logger = LoggerFactory.getLogger(getClass());
+    private static final SpiderMonitor INSTANCE = new SpiderMonitor();
 
     private MBeanServer mbeanServer;
 
     private String jmxServerName;
 
-    private List<SpiderStatusMXBean> spiderStatuses = new ArrayList<SpiderStatusMXBean>();
+    private List<SpiderStatusMXBean> spiderStatuses = new ArrayList<>();
 
     protected SpiderMonitor() {
         jmxServerName = "WebMagic";
@@ -51,7 +51,7 @@ public class SpiderMonitor {
         for (Spider spider : spiders) {
             MonitorSpiderListener monitorSpiderListener = new MonitorSpiderListener();
             if (spider.getSpiderListeners() == null) {
-                List<SpiderListener> spiderListeners = new ArrayList<SpiderListener>();
+                List<SpiderListener> spiderListeners = new ArrayList<>();
                 spiderListeners.add(monitorSpiderListener);
                 spider.setSpiderListeners(spiderListeners);
             } else {
@@ -90,7 +90,7 @@ public class SpiderMonitor {
         }
 
         @Override
-        public void onError(Request request) {
+        public void onError(Request request, Exception e) {
             errorUrls.add(request.getUrl());
             errorCount.incrementAndGet();
         }
@@ -109,7 +109,6 @@ public class SpiderMonitor {
     }
 
     protected void registerMBean(SpiderStatusMXBean spiderStatus) throws MalformedObjectNameException, InstanceAlreadyExistsException, MBeanRegistrationException, NotCompliantMBeanException {
-//        ObjectName objName = new ObjectName(jmxServerName + ":name=" + spiderStatus.getName());
         ObjectName objName = new ObjectName(jmxServerName + ":name=" + UrlUtils.removePort(spiderStatus.getName()));
         mbeanServer.registerMBean(spiderStatus, objName);
     }