diff --git a/demo/httpreq/curl_test.go b/demo/httpreq/post-file_test.go
similarity index 71%
rename from demo/httpreq/curl_test.go
rename to demo/httpreq/post-file_test.go
index 8498c0c..bc9474a 100644
--- a/demo/httpreq/curl_test.go
+++ b/demo/httpreq/post-file_test.go
@@ -7,15 +7,15 @@ import (
 	"github.com/ahuigo/gohttptool/httpreq"
 )
 
-func TestCurl(t *testing.T) {
+func TestPostFile(t *testing.T) {
 	curl, err := httpreq.R().
-		SetParams(map[string]string{"p": "1"}).
-		SetData(map[string]string{"key": "xx"}).
+		SetQueryParams(map[string]string{"p": "1"}).
+		SetFormData(map[string]string{"key": "xx"}).
 		SetAuthBasic("user", "pass").
 		SetHeader("header1", "value1").
 		AddCookieKV("count", "1").
 		AddFileHeader("file", "test.txt", []byte("hello world")).
-		AddFileHeader("file2", "test.txt", []byte("hello world2")).
+		AddFile("file2", getTestDataPath("a.txt")).
 		SetReq("GET", "/path").
 		ToCurl()
 	if err != nil {
diff --git a/demo/httpreq/post_test.go b/demo/httpreq/post_test.go
new file mode 100644
index 0000000..3dd4783
--- /dev/null
+++ b/demo/httpreq/post_test.go
@@ -0,0 +1,103 @@
+package httpreq
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/ahuigo/gohttptool/httpreq"
+)
+
+type MapString = map[string]string
+
+// POST: curl -X POST -d ” 'http://local/post?p=1'
+func TestPostParams(t *testing.T) {
+	curl, err := httpreq.R().
+		SetQueryParams(map[string]string{"p": "1"}).
+		SetReq("POST", "http://local/post").
+		ToCurl()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.HasPrefix(curl, "curl ") ||
+		!strings.Contains(curl, "?p=1") {
+		t.Fatal("bad curl: ", curl)
+	} else {
+		t.Log(curl)
+	}
+}
+
+// POST: curl -X POST -H 'Content-Type: application/json' -d '{"name":"ahuigo"}' http://localhost/path
+func TestPostJson(t *testing.T) {
+	curl, err := httpreq.R().
+		SetJson(map[string]string{"name": "ahuigo"}).
+		SetReq("POST", "/path").
+		ToCurl()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.HasPrefix(curl, "curl ") ||
+		!strings.Contains(curl, `'Content-Type: application/json`) ||
+		!strings.Contains(curl, `{"name":"ahuigo"}`) {
+		t.Fatal("bad curl: ", curl)
+	} else {
+		t.Log(curl)
+	}
+}
+
+// Post Data: curl -H 'Content-Type: application/x-www-form-urlencoded' http://local/post -d 'name=Alex'
+func TestPostFormUrlEncode(t *testing.T) {
+	curl, err := httpreq.R().
+		SetFormData(map[string]string{"name": "Alex"}).
+		SetReq("POST", "http://local/post").
+		ToCurl()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.HasPrefix(curl, "curl ") ||
+		!strings.Contains(curl, `'Content-Type: application/x-www-form-urlencode`) ||
+		!strings.Contains(curl, "name=Alex") {
+		t.Fatal("bad curl: ", curl)
+	} else {
+		t.Log(curl)
+	}
+
+}
+
+// POST FormData: multipart/form-data; boundary=....
+// curl http://local/post -F 'name=Alex'
+func TestPostFormMultipart(t *testing.T) {
+	curl, err := httpreq.R().
+		SetIsMultiPart(true).
+		SetFormData(map[string]string{"name": "Alex"}).
+		SetReq("POST", "http://local/post").
+		ToCurl()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.HasPrefix(curl, "curl ") ||
+		!strings.Contains(curl, `'Content-Type: multipart/form-data`) ||
+		!strings.Contains(curl, `name="name"`) {
+		t.Fatal("bad curl: ", curl)
+	} else {
+		println(curl)
+	}
+}
+
+// POST: curl -X POST -H 'Content-Type: text/plain' -d 'hello!' http://local/post
+func TestPostPlainData(t *testing.T) {
+	curl, err := httpreq.R().
+		SetContentType(httpreq.ContentTypePlain).
+		SetBody([]byte("hello!")).
+		SetReq("POST", "http://local/post").
+		ToCurl()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.HasPrefix(curl, "curl ") ||
+		!strings.Contains(curl, `'Content-Type: text/plain`) ||
+		!strings.Contains(curl, `-d 'hello!'`) {
+		t.Fatal("bad curl: ", curl)
+	} else {
+		println(curl)
+	}
+}
diff --git a/demo/httpreq/testdata/a.txt b/demo/httpreq/testdata/a.txt
new file mode 100644
index 0000000..a3828ba
--- /dev/null
+++ b/demo/httpreq/testdata/a.txt
@@ -0,0 +1,2 @@
+
+I'm a.txt
\ No newline at end of file
diff --git a/demo/httpreq/util_test.go b/demo/httpreq/util_test.go
new file mode 100644
index 0000000..23b1eae
--- /dev/null
+++ b/demo/httpreq/util_test.go
@@ -0,0 +1,11 @@
+package httpreq
+
+import (
+	"os"
+	"path/filepath"
+)
+
+func getTestDataPath(filename string) string {
+	pwd, _ := os.Getwd()
+	return filepath.Join(pwd, "./testdata", filename)
+}
diff --git a/go.mod b/go.mod
index 517ba10..81f020e 100644
--- a/go.mod
+++ b/go.mod
@@ -1,5 +1,5 @@
 module github.com/ahuigo/gohttptool
 
-go 1.22.1
+go 1.21.1
 
 require github.com/pkg/errors v0.9.1
diff --git a/httpreq/curl.go b/httpreq/curl.go
index 1cc491c..b9fa9ed 100644
--- a/httpreq/curl.go
+++ b/httpreq/curl.go
@@ -15,6 +15,7 @@ import (
 func (r *RequestBuilder) FromCurl(curl string) {
 
 }
+
 func (r *RequestBuilder) ToCurl() (curl string, err error) {
 	if httpreq, err := r.ToRequest(); err != nil {
 		return "", err
@@ -24,36 +25,39 @@ func (r *RequestBuilder) ToCurl() (curl string, err error) {
 	}
 }
 
-func buildCurlRequest(req *http.Request, httpCookiejar http.CookieJar) (curl string) {
+func buildCurlRequest(req *http.Request, httpCookiejar http.CookieJar) (curlString string) {
+	buf := acquireBuffer()
+	defer releaseBuffer(buf)
+
 	// 1. Generate curl raw headers
-	curl = "curl -X " + req.Method + " "
+	buf.WriteString("curl -X " + req.Method + " ")
 	// req.Host + req.URL.Path + "?" + req.URL.RawQuery + " " + req.Proto + " "
 	headers := dumpCurlHeaders(req)
 	for _, kv := range *headers {
-		curl += `-H ` + shell.Quote(kv[0]+": "+kv[1]) + ` `
+		buf.WriteString(`-H ` + shell.Quote(kv[0]+": "+kv[1]) + ` `)
 	}
 
 	// 2. Generate curl cookies
 	if cookieJar, ok := httpCookiejar.(*cookiejar.Jar); ok {
 		cookies := cookieJar.Cookies(req.URL)
 		if len(cookies) > 0 {
-			curl += ` -H ` + shell.Quote(dumpCurlCookies(cookies)) + " "
+			buf.WriteString(` -H ` + shell.Quote(dumpCurlCookies(cookies)) + " ")
 		}
 	}
 
 	// 3. Generate curl body
 	if req.Body != nil {
-		buf, _ := io.ReadAll(req.Body)
-		req.Body = io.NopCloser(bytes.NewBuffer(buf)) // important!!
-		curl += `-d ` + shell.Quote(string(buf))
+		buf2, _ := io.ReadAll(req.Body)
+		req.Body = io.NopCloser(bytes.NewBuffer(buf2)) // important!!
+		buf.WriteString(`-d ` + shell.Quote(string(buf2)))
 	}
 
 	urlString := shell.Quote(req.URL.String())
 	if urlString == "''" {
 		urlString = "'http://unexecuted-request'"
 	}
-	curl += " " + urlString
-	return curl
+	buf.WriteString(" " + urlString)
+	return buf.String()
 }
 
 // dumpCurlCookies dumps cookies to curl format
@@ -64,6 +68,7 @@ func dumpCurlCookies(cookies []*http.Cookie) string {
 		sb.WriteString(cookie.Name + "=" + url.QueryEscape(cookie.Value) + "&")
 	}
 	return strings.TrimRight(sb.String(), "&")
+
 }
 
 // dumpCurlHeaders dumps headers to curl format
diff --git a/httpreq/req-builder.go b/httpreq/req-builder.go
index 9f38527..192a527 100644
--- a/httpreq/req-builder.go
+++ b/httpreq/req-builder.go
@@ -16,8 +16,15 @@ import (
 func (rb *RequestBuilder) ToRequest() (*http.Request, error) {
 	var dataType = ContentType(rb.rawreq.Header.Get("Content-Type"))
 	var origurl = rb.url
-	if len(rb.files) > 0 || len(rb.fileHeaders) > 0 {
+	if rb.isMultiPart || len(rb.files) > 0 || len(rb.fileHeaders) > 0 {
 		dataType = ContentTypeFormData
+	} else if rb.json != nil {
+		dataType = ContentTypeJson
+	} else if len(rb.formData) > 0 {
+		dataType = ContentTypeFormEncode
+	}
+	if dataType != "" {
+		rb.rawreq.Header.Set("Content-Type", string(dataType))
 	}
 
 	URL, err := rb.buildURLParams(origurl)
@@ -30,14 +37,16 @@ func (rb *RequestBuilder) ToRequest() (*http.Request, error) {
 	}
 
 	switch dataType {
+	case ContentTypeJson:
+		rb.setBodyJson()
 	case ContentTypeFormEncode:
-		if len(rb.datas) > 0 {
-			formEncodeValues := rb.buildFormEncode(rb.datas)
-			rb.setBodyFormEncode(formEncodeValues)
+		if len(rb.formData) > 0 {
+			rb.setBodyFormEncode(rb.formData)
 		}
 	case ContentTypeFormData:
 		// multipart/form-data
 		rb.buildFilesAndForms()
+	default:
 	}
 
 	if rb.rawreq.Body == nil && rb.rawreq.Method != "GET" {
@@ -49,25 +58,26 @@ func (rb *RequestBuilder) ToRequest() (*http.Request, error) {
 	return rb.rawreq, nil
 }
 
-// build post Form encode
-func (rb *RequestBuilder) buildFormEncode(datas map[string]string) (Forms url.Values) {
-	Forms = url.Values{}
-	for key, value := range datas {
-		Forms.Add(key, value)
-	}
-	return Forms
-}
-
 // set form urlencode
-func (rb *RequestBuilder) setBodyFormEncode(Forms url.Values) {
-	data := Forms.Encode()
+func (rb *RequestBuilder) setBodyFormEncode(formData url.Values) {
+	data := formData.Encode()
 	rb.rawreq.Body = io.NopCloser(strings.NewReader(data))
 	rb.rawreq.ContentLength = int64(len(data))
 }
 
+func (rb *RequestBuilder) setBodyJson() {
+	bodyBuf, err := noescapeJSONMarshalIndent(&rb.json)
+	if err == nil {
+		prtBodyBytes := bodyBuf.Bytes()
+		plen := len(prtBodyBytes)
+		if plen > 0 && prtBodyBytes[plen-1] == '\n' {
+			prtBodyBytes = prtBodyBytes[:plen-1]
+		}
+		rb.rawreq.Body = io.NopCloser(bytes.NewReader(prtBodyBytes))
+	}
+}
+
 func (rb *RequestBuilder) buildURLParams(userURL string) (*url.URL, error) {
-	params := rb.params
-	paramsArray := rb.paramsList
 	if strings.HasPrefix(userURL, "/") {
 		userURL = "http://localhost" + userURL
 	} else if userURL == "" {
@@ -81,13 +91,9 @@ func (rb *RequestBuilder) buildURLParams(userURL string) (*url.URL, error) {
 
 	values := parsedURL.Query()
 
-	for key, value := range params {
-		values.Set(key, value)
-	}
-	for key, vals := range paramsArray {
-		for _, v := range vals {
-			values.Add(key, v)
-		}
+	for key, value := range rb.queryParam {
+		values[key] = value
+		// values.Set(key, value[0])
 	}
 	parsedURL.RawQuery = values.Encode()
 	return parsedURL, nil
@@ -95,14 +101,16 @@ func (rb *RequestBuilder) buildURLParams(userURL string) (*url.URL, error) {
 
 func (rb *RequestBuilder) buildFilesAndForms() error {
 	files := rb.files
-	datas := rb.datas
+	formData := rb.formData
 	filesHeaders := rb.fileHeaders
 	//handle file multipart
 	var b bytes.Buffer
 	w := multipart.NewWriter(&b)
 
-	for k, v := range datas {
-		w.WriteField(k, v)
+	for k, v := range formData {
+		for _, vv := range v {
+			w.WriteField(k, vv)
+		}
 	}
 
 	for field, path := range files {
diff --git a/httpreq/req.go b/httpreq/req.go
index d422027..644f4c8 100644
--- a/httpreq/req.go
+++ b/httpreq/req.go
@@ -1,9 +1,12 @@
 package httpreq
 
 import (
+	"bytes"
 	"context"
+	"io"
 	"net/http"
 	"net/textproto"
+	"net/url"
 )
 
 type ContentType string
@@ -27,13 +30,15 @@ type fileHeader struct {
 }
 
 type RequestBuilder struct {
-	rawreq      *http.Request
-	url         string
+	rawreq *http.Request
+	url    string
+
+	queryParam  url.Values
+	formData    url.Values
+	isMultiPart bool
+	json        any
 	files       map[string]string     // field -> path
 	fileHeaders map[string]fileHeader // field -> contents
-	datas       map[string]string     // key -> value
-	params      map[string]string     // key -> value
-	paramsList  map[string][]string   // key -> value list
 }
 
 func R() *RequestBuilder {
@@ -45,11 +50,11 @@ func R() *RequestBuilder {
 			ProtoMajor: 1,
 			ProtoMinor: 1,
 		},
+		queryParam: make(url.Values),
+		formData:   make(map[string][]string),
+		// paramsList:  make(map[string][]string),
 		files:       make(map[string]string),
 		fileHeaders: make(map[string]fileHeader),
-		datas:       make(map[string]string),
-		params:      make(map[string]string),
-		paramsList:  make(map[string][]string),
 	}
 }
 
@@ -69,6 +74,11 @@ func (r *RequestBuilder) SetAuthBearer(token string) *RequestBuilder {
 	return r
 }
 
+func (r *RequestBuilder) SetContentType(ct ContentType) *RequestBuilder {
+	r.rawreq.Header.Set("Content-Type", string(ct))
+	return r
+}
+
 func (r *RequestBuilder) AddCookies(cookies []*http.Cookie) *RequestBuilder {
 	for _, cookie := range cookies {
 		r.rawreq.AddCookie(cookie)
@@ -84,6 +94,7 @@ func (r *RequestBuilder) AddCookieKV(name, value string) *RequestBuilder {
 	return r
 }
 
+/************** params **********************/
 /************** file **********************/
 func (r *RequestBuilder) AddFile(fieldname, path string) *RequestBuilder {
 	r.files[fieldname] = path
@@ -110,16 +121,67 @@ func (r *RequestBuilder) SetReq(method string, url string) *RequestBuilder {
 	return r
 }
 
-func (r *RequestBuilder) SetParams(params map[string]string) *RequestBuilder {
-	r.params = params
+/************** params **********************/
+func (r *RequestBuilder) SetQueryParams(params map[string]string) *RequestBuilder {
+	for p, v := range params {
+		r.SetQueryParam(p, v)
+	}
+	return r
+}
+func (r *RequestBuilder) SetQueryParam(param, value string) *RequestBuilder {
+	r.queryParam.Set(param, value)
 	return r
 }
 
-func (r *RequestBuilder) SetData(data map[string]string) *RequestBuilder {
-	r.datas = data
+func (r *RequestBuilder) SetQueryParamsFromValues(params url.Values) *RequestBuilder {
+	for p, v := range params {
+		for _, pv := range v {
+			r.queryParam.Add(p, pv)
+		}
+	}
+	return r
+}
+
+/************** body(bytes) **********************/
+func (r *RequestBuilder) SetBody(body []byte) *RequestBuilder {
+	r.rawreq.Body = io.NopCloser(bytes.NewReader(body))
 	return r
 }
 
+/************** body(form) **********************/
+// Set Form data(encode or multipart)
+func (r *RequestBuilder) SetIsMultiPart(b bool) *RequestBuilder {
+	r.isMultiPart = b
+	return r
+}
+func (r *RequestBuilder) SetFormData(data map[string]string) *RequestBuilder {
+	for k, v := range data {
+		r.formData.Set(k, v)
+	}
+	return r
+}
+
+// SetFormDataFromValues method appends multiple form parameters with multi-value
+//
+//	SetFormDataFromValues(url.Values{"words": []string{"book", "glass", "pencil"},})
+func (r *RequestBuilder) SetFormDataFromValues(data url.Values) *RequestBuilder {
+	for k, v := range data {
+		for _, kv := range v {
+			r.formData.Add(k, kv)
+		}
+	}
+	return r
+}
+
+/************** body(json) **********************/
+func (r *RequestBuilder) SetJson(data any) *RequestBuilder {
+	r.json = data
+	return r
+}
+
+/************** body(plain) **********************/
+
+/************** utils **********************/
 func (r *RequestBuilder) GetRawreq() *http.Request {
 	return r.rawreq
 }
diff --git a/httpreq/utils.go b/httpreq/utils.go
new file mode 100644
index 0000000..e6a090b
--- /dev/null
+++ b/httpreq/utils.go
@@ -0,0 +1,35 @@
+package httpreq
+
+import (
+	"bytes"
+	"encoding/json"
+	"sync"
+)
+
+var (
+	bufPool = &sync.Pool{New: func() interface{} { return &bytes.Buffer{} }}
+)
+
+var noescapeJSONMarshalIndent = func(v interface{}) (*bytes.Buffer, error) {
+	buf := acquireBuffer()
+	encoder := json.NewEncoder(buf)
+	encoder.SetEscapeHTML(false)
+	// encoder.SetIndent("", "   ")
+
+	if err := encoder.Encode(v); err != nil {
+		releaseBuffer(buf)
+		return nil, err
+	}
+	return buf, nil
+}
+
+func acquireBuffer() *bytes.Buffer {
+	return bufPool.Get().(*bytes.Buffer)
+}
+
+func releaseBuffer(buf *bytes.Buffer) {
+	if buf != nil {
+		buf.Reset()
+		bufPool.Put(buf)
+	}
+}
diff --git a/version b/version
index 837042c..254a9f2 100644
--- a/version
+++ b/version
@@ -1 +1 @@
-v0.0.5
\ No newline at end of file
+v0.0.6
\ No newline at end of file