RetResult增加successFuture方法

src/org/redkale/service/RetResult.java

@@ -6,6 +6,7 @@
 package org.redkale.service;
 
 import java.util.*;
+import java.util.concurrent.CompletableFuture;
 import org.redkale.convert.json.*;
 
 /**
@@ -57,6 +58,10 @@ public class RetResult<T> {
         return new RetResult();
     }
 
+    public static <T> CompletableFuture<RetResult<T>> successFuture() {
+        return CompletableFuture.completedFuture(new RetResult());
+    }
+
     /**
      * 判断结果是否成功返回， retcode = 0 视为成功， 否则视为错误码
      *