diff --git a/plugin-default-impl/nacos-default-auth-plugin/src/main/java/com/alibaba/nacos/plugin/auth/impl/persistence/handler/PageHandlerAdapterFactory.java b/plugin-default-impl/nacos-default-auth-plugin/src/main/java/com/alibaba/nacos/plugin/auth/impl/persistence/handler/PageHandlerAdapterFactory.java
index 37dc4be6983..50f8e428b04 100644
--- a/plugin-default-impl/nacos-default-auth-plugin/src/main/java/com/alibaba/nacos/plugin/auth/impl/persistence/handler/PageHandlerAdapterFactory.java
+++ b/plugin-default-impl/nacos-default-auth-plugin/src/main/java/com/alibaba/nacos/plugin/auth/impl/persistence/handler/PageHandlerAdapterFactory.java
@@ -24,6 +24,8 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Collections;
+import java.util.function.Consumer;
 
 /**
  * pagination factory.
@@ -31,54 +33,43 @@
  * @author huangKeMing
  */
 public class PageHandlerAdapterFactory {
-    
-    private static PageHandlerAdapterFactory instance;
-    
-    private List<PageHandlerAdapter> handlerAdapters;
-    
-    private Map<String, PageHandlerAdapter> handlerAdapterMap;
-    
+
+    private final List<PageHandlerAdapter> handlerAdapters;
+
+    private final Map<String, PageHandlerAdapter> handlerAdapterMap;
+
     public List<PageHandlerAdapter> getHandlerAdapters() {
         return handlerAdapters;
     }
-    
+
     public Map<String, PageHandlerAdapter> getHandlerAdapterMap() {
         return handlerAdapterMap;
     }
-    
+
     private PageHandlerAdapterFactory() {
-        handlerAdapters = new ArrayList<>(3);
-        handlerAdapterMap = new HashMap<>(3);
-        initHandlerAdapters();
-    }
-    
-    public static PageHandlerAdapterFactory getInstance() {
-        if (instance == null) {
-            synchronized (PageHandlerAdapterFactory.class) {
-                if (instance == null) {
-                    instance = new PageHandlerAdapterFactory();
-                }
-            }
-        }
-        return instance;
-    }
-    
-    /**
-     * init handler adapters.
-     */
-    private void initHandlerAdapters() {
+        List<PageHandlerAdapter> handlerAdapters = new ArrayList<>(3);
+        Map<String, PageHandlerAdapter> handlerAdapterMap = new HashMap<>(3);
+        Consumer<PageHandlerAdapter> addHandlerAdapter = handlerAdapter -> {
+            handlerAdapters.add(handlerAdapter);
+            handlerAdapterMap.put(handlerAdapter.getClass().getName(), handlerAdapter);
+        };
         // MysqlPageHandlerAdapter
-        addHandlerAdapter(new MysqlPageHandlerAdapter());
+        addHandlerAdapter.accept(new MysqlPageHandlerAdapter());
         // DerbyPageHandlerAdapter
-        addHandlerAdapter(new DerbyPageHandlerAdapter());
+        addHandlerAdapter.accept(new DerbyPageHandlerAdapter());
         // DefaultPageHandlerAdapter
-        addHandlerAdapter(new DefaultPageHandlerAdapter());
+        addHandlerAdapter.accept(new DefaultPageHandlerAdapter());
+        this.handlerAdapters = Collections.unmodifiableList(handlerAdapters);
+        this.handlerAdapterMap = Collections.unmodifiableMap(handlerAdapterMap);
+    }
+
+    private static final class InstanceHolder {
+        static final PageHandlerAdapterFactory INSTANCE = new PageHandlerAdapterFactory();
     }
-    
-    private void addHandlerAdapter(PageHandlerAdapter handlerAdapter) {
-        handlerAdapters.add(handlerAdapter);
-        handlerAdapterMap.put(handlerAdapter.getClass().getName(), handlerAdapter);
+
+    public static PageHandlerAdapterFactory getInstance() {
+        return InstanceHolder.INSTANCE;
     }
-    
+
 }