diff --git a/codec/context.go b/codec/context.go
index 360a752..1ffedb6 100644
--- a/codec/context.go
+++ b/codec/context.go
@@ -2,6 +2,7 @@ package codec
 
 import (
 	"context"
+	"io"
 	"net/http"
 )
 
@@ -13,6 +14,6 @@ type Context interface {
 
 type Codec interface {
 	Mime() string
-	EncodeResponse(ctx Context, v any) error
-	DecodeRequest(ctx Context, v any) error
+	Encode(ctx context.Context, w io.Writer, v any) error
+	Decode(ctx context.Context, r io.Reader, v any) error
 }
diff --git a/codec/default.go b/codec/default.go
index 8736d55..cb2f3ae 100644
--- a/codec/default.go
+++ b/codec/default.go
@@ -1,7 +1,9 @@
 package codec
 
 import (
+	"context"
 	"encoding/json"
+	"io"
 
 	"gopkg.in/yaml.v3"
 )
@@ -12,12 +14,12 @@ func (JSON) Mime() string {
 	return "application/json"
 }
 
-func (JSON) DecodeRequest(ctx Context, v any) error {
-	return json.NewDecoder(ctx.Request().Body).Decode(v)
+func (JSON) Decode(ctx context.Context, r io.Reader, v any) error {
+	return json.NewDecoder(r).Decode(v)
 }
 
-func (JSON) EncodeResponse(ctx Context, v any) error {
-	return json.NewEncoder(ctx.ResponseWriter()).Encode(v)
+func (JSON) Encode(ctx context.Context, w io.Writer, v any) error {
+	return json.NewEncoder(w).Encode(v)
 }
 
 type YAML struct{}
@@ -26,12 +28,12 @@ func (YAML) Mime() string {
 	return "application/yaml"
 }
 
-func (YAML) DecodeRequest(ctx Context, v any) error {
-	return yaml.NewDecoder(ctx.Request().Body).Decode(v)
+func (YAML) Decode(ctx context.Context, r io.Reader, v any) error {
+	return yaml.NewDecoder(r).Decode(v)
 }
 
-func (YAML) EncodeResponse(ctx Context, v any) error {
-	encoder := yaml.NewEncoder(ctx.ResponseWriter())
+func (YAML) Encode(ctx context.Context, w io.Writer, v any) error {
+	encoder := yaml.NewEncoder(w)
 	defer encoder.Close()
 
 	return encoder.Encode(v)
diff --git a/codec/module.go b/codec/module.go
index 6b70272..116d221 100644
--- a/codec/module.go
+++ b/codec/module.go
@@ -67,3 +67,11 @@ func (c *Codecs) getCodec(ctx Context, head string) Codec {
 
 	return ret
 }
+
+func (c *Codecs) DecodeRequest(ctx Context, v any) error {
+	return c.Request(ctx).Decode(ctx, ctx.Request().Body, v)
+}
+
+func (c *Codecs) EncodeResponse(ctx Context, v any) error {
+	return c.Response(ctx).Encode(ctx, ctx.ResponseWriter(), v)
+}
diff --git a/examples_test.go b/examples_test.go
index f2937c4..06ac7ba 100644
--- a/examples_test.go
+++ b/examples_test.go
@@ -1,10 +1,14 @@
 package espresso_test
 
 import (
+	"bytes"
+	"encoding/json"
 	"fmt"
 	"net/http"
+	"net/http/httptest"
 
 	"github.com/googollee/go-espresso"
+	"github.com/googollee/go-espresso/codec"
 )
 
 type Book struct {
@@ -38,9 +42,11 @@ func ExampleEspresso() {
 			return espresso.Error(http.StatusNotFound, fmt.Errorf("not found"))
 		}
 
-		if err := codec.Response(ctx).Encode(ctx, &book); err != nil {
+		if err := codec.Module.Value(ctx).EncodeResponse(ctx, &book); err != nil {
 			return err
 		}
+
+		return nil
 	})
 
 	espo.Handle(func(ctx espresso.Context) error {
@@ -49,16 +55,60 @@ func ExampleEspresso() {
 			return err
 		}
 
+		codecs := codec.Module.Value(ctx)
+
 		var book Book
-		if err := codec.Request(ctx).Decode(ctx, &book); err != nil {
+		if err := codecs.DecodeRequest(ctx, &book); err != nil {
 			return espresso.Error(http.StatusBadRequest, err)
 		}
 
 		book.ID = len(books)
 		books[book.ID] = book
 
-		if err := codec.Response(ctx).Decode(ctx, &book); err != nil {
+		if err := codecs.EncodeResponse(ctx, &book); err != nil {
 			return err
 		}
+
+		return nil
 	})
+
+	svr := httptest.NewServer(espo)
+	defer svr.Close()
+
+	func() {
+		var book Book
+		resp, err := http.Get(svr.URL + "/book/1")
+		if err != nil {
+			panic(err)
+		}
+		defer resp.Body.Close()
+
+		if err := json.NewDecoder(resp.Body).Decode(&book); err != nil {
+			panic(err)
+		}
+
+		fmt.Println("book(1) title:", book.Title)
+	}()
+
+	func() {
+		arg := Book{Title: "The New Book"}
+
+		var buf bytes.Buffer
+		if err := json.NewEncoder(&buf).Encode(&arg); err != nil {
+			panic(err)
+		}
+
+		resp, err := http.Post(svr.URL+"/book/1", "application/json", &buf)
+		if err != nil {
+			panic(err)
+		}
+		defer resp.Body.Close()
+
+		var ret Book
+		if err := json.NewDecoder(resp.Body).Decode(&ret); err != nil {
+			panic(err)
+		}
+
+		fmt.Println(ret.Title, " id:", ret.ID)
+	}()
 }