refactory code

apm-sniffer/apm-sdk-plugin/mysql-5.x-plugin/src/main/java/org/skywalking/apm/plugin/jdbc/mysql/define/ConnectionInstrumentation.java

@@ -49,8 +49,6 @@ import static org.skywalking.apm.plugin.jdbc.define.Constants.SERVICE_METHOD_INT
  */
 public abstract class ConnectionInstrumentation extends ClassInstanceMethodsEnhancePluginDefine {
 
-    public static final String ENHANCE_CLASS = "com.mysql.jdbc.ConnectionImpl";
-
     @Override protected ConstructorInterceptPoint[] getConstructorsInterceptPoints() {
         return new ConstructorInterceptPoint[0];
     }

apm-sniffer/apm-sdk-plugin/mysql-5.x-plugin/src/main/java/org/skywalking/apm/plugin/jdbc/mysql/define/Mysql5xConnectionInstrumentation.java

@@ -29,7 +29,11 @@ import static org.skywalking.apm.plugin.jdbc.mysql.define.MultiClassNameMatch.by
  * @author zhangxin
  */
 public class Mysql5xConnectionInstrumentation extends ConnectionInstrumentation {
+    public static final String ENHANCE_CLASS = "com.mysql.jdbc.ConnectionImpl";
+
+    public static final String CJ_JDBC_ENHANCE_CLASS = "com.mysql.cj.jdbc.ConnectionImpl";
+
     @Override protected ClassMatch enhanceClass() {
-        return byMultiClassMatch(ENHANCE_CLASS, "com.mysql.cj.jdbc.ConnectionImpl");
+        return byMultiClassMatch(ENHANCE_CLASS, CJ_JDBC_ENHANCE_CLASS);
     }
 }