change variable name ,make it easy to understand (#2647)

Co-authored-by: dailidong <dailidong66@gmail.com>

dolphinscheduler-alert/src/main/java/org/apache/dolphinscheduler/alert/plugin/EmailAlertPlugin.java

@@ -56,7 +56,7 @@ public class EmailAlertPlugin implements AlertPlugin {
 
     @Override
     public String getId() {
-        return Constants.PLUGIN_DEFAULT_EMAIL;
+        return Constants.PLUGIN_DEFAULT_EMAIL_ID;
     }
 
     @Override

dolphinscheduler-alert/src/main/java/org/apache/dolphinscheduler/alert/runner/AlertSender.java

@@ -80,7 +80,7 @@ public class AlertSender {
 
             alertInfo.addProp("receivers", receviersList);
 
-            AlertPlugin emailPlugin = pluginManager.findOne(Constants.PLUGIN_DEFAULT_EMAIL);
+            AlertPlugin emailPlugin = pluginManager.findOne(Constants.PLUGIN_DEFAULT_EMAIL_ID);
             retMaps = emailPlugin.process(alertInfo);
 
             if (retMaps == null) {

dolphinscheduler-alert/src/main/java/org/apache/dolphinscheduler/alert/utils/Constants.java

@@ -179,7 +179,7 @@ public class Constants {
      */
     public static final String PLUGIN_DIR = "plugin.dir";
 
-    public static final String PLUGIN_DEFAULT_EMAIL = "email";
+    public static final String PLUGIN_DEFAULT_EMAIL_ID = "email";
 
     public static final String PLUGIN_DEFAULT_EMAIL_CH = "邮件";
 

dolphinscheduler-alert/src/test/java/org/apache/dolphinscheduler/alert/plugin/EmailAlertPluginTest.java

@@ -47,7 +47,7 @@ public class EmailAlertPluginTest {
     @Test
     public void getId() {
         String id = plugin.getId();
-        assertEquals(Constants.PLUGIN_DEFAULT_EMAIL, id);
+        assertEquals(Constants.PLUGIN_DEFAULT_EMAIL_ID, id);
     }
 
     @Test

dolphinscheduler-common/src/main/java/org/apache/dolphinscheduler/common/plugin/FilePluginManager.java

@@ -90,8 +90,8 @@ public class FilePluginManager implements PluginManager {
     }
 
     @Override
-    public AlertPlugin findOne(String name) {
+    public AlertPlugin findOne(String pluginId) {
-        return pluginMap.get(name);
+        return pluginMap.get(pluginId);
     }
 
     @Override