diff --git a/utils/math2/math.go b/utils/math2/math.go
index 7a8508b..4e6d268 100644
--- a/utils/math2/math.go
+++ b/utils/math2/math.go
@@ -72,3 +72,12 @@ func SplitN[T constraints.Integer](v T, n int) []T {
 
 	return result
 }
+
+// 除法，如果除数为0，则返回默认值
+func DivOrDefault[T constraints.Integer | constraints.Float](v, d T, def T) T {
+	if d == 0 {
+		return def
+	}
+
+	return v / d
+}
diff --git a/utils/serder/serder.go b/utils/serder/serder.go
index d3cfcd4..c665201 100644
--- a/utils/serder/serder.go
+++ b/utils/serder/serder.go
@@ -65,6 +65,9 @@ func JSONToObjectExRaw(data []byte, ret any) error {
 }
 
 // 将JSON字符串转为对象。支持TypeUnion。
+//
+// 如果发现反序列化后的结果不对，但没有返回错误，可以考虑是JSON字符串有问题，
+// 尤其是在反序列化嵌套的TypeUnion时，如果内部的TypeUnion反序列化失败，错误是不会传递出来的（库的缺陷）
 func JSONToObjectStreamEx[T any](stream io.Reader) (T, error) {
 	var ret T
 	dec := defaultAPI.NewDecoder(stream)
diff --git a/utils/serder/serder_test.go b/utils/serder/serder_test.go
index b36c0d1..abd7aef 100644
--- a/utils/serder/serder_test.go
+++ b/utils/serder/serder_test.go
@@ -665,3 +665,32 @@ func Test_ObjectToJSON3(t *testing.T) {
 		// So(ret, ShouldResemble, val)
 	})
 }
+
+type BaseCallback interface{}
+type StCallback struct {
+	Metadata `union:"StCallback"`
+	Type     string
+	Value    string
+}
+
+func (st *StCallback) OnUnionSerializing() {
+	st.Value = "called"
+	st.Type = "StCallback"
+}
+
+func Test_ObjectToJSONEx4(t *testing.T) {
+	Convey("序列化Callback", t, func() {
+		union := types.NewTypeUnion[BaseCallback](&StCallback{})
+		UseTypeUnionInternallyTagged(&union, "Type")
+
+		val := []BaseCallback{&StCallback{}}
+		data, err := ObjectToJSONEx(val)
+		So(err, ShouldBeNil)
+
+		ret, err := JSONToObjectEx[[]BaseCallback](data)
+		So(err, ShouldBeNil)
+
+		So(len(ret), ShouldEqual, 1)
+		So(ret[0].(*StCallback).Value, ShouldEqual, "called")
+	})
+}
diff --git a/utils/serder/types/types.go b/utils/serder/types/types.go
index 0046926..a1cd975 100644
--- a/utils/serder/types/types.go
+++ b/utils/serder/types/types.go
@@ -1,3 +1,7 @@
 package types
 
 type Metadata struct{}
+
+type OnUnionSerializing interface {
+	OnUnionSerializing()
+}
diff --git a/utils/serder/union_handler.go b/utils/serder/union_handler.go
index cd98a02..dd6fb16 100644
--- a/utils/serder/union_handler.go
+++ b/utils/serder/union_handler.go
@@ -8,6 +8,7 @@ import (
 	jsoniter "github.com/json-iterator/go"
 	"github.com/modern-go/reflect2"
 	"gitlink.org.cn/cloudream/common/pkgs/types"
+	sertypes "gitlink.org.cn/cloudream/common/utils/serder/types"
 
 	ref2 "gitlink.org.cn/cloudream/common/utils/reflect2"
 )
@@ -211,6 +212,12 @@ func (e *InternallyTaggedEncoder) Encode(ptr unsafe.Pointer, stream *jsoniter.St
 		val = reflect2.IFaceToEFace(ptr)
 	}
 
+	if val != nil {
+		if on, ok := val.(sertypes.OnUnionSerializing); ok {
+			on.OnUnionSerializing()
+		}
+	}
+
 	// 可以考虑检查一下Type字段有没有赋值，没有赋值则将其赋值为union Tag指定的值
 	stream.WriteVal(val)
 }
@@ -292,6 +299,10 @@ func (e *ExternallyTaggedEncoder) Encode(ptr unsafe.Pointer, stream *jsoniter.St
 		return
 	}
 
+	if on, ok := val.(sertypes.OnUnionSerializing); ok {
+		on.OnUnionSerializing()
+	}
+
 	stream.WriteObjectStart()
 	valType := ref2.TypeOfValue(val)
 	if !e.union.Union.Include(valType) {