update doc

README.md

@@ -5,3 +5,94 @@ Generic tool to validate input json string and check the parameters
 In most of the micro-service application, we use json to deliver data from one to another, but validating the parameter in json is always boring, so this tool will give you a big help. It can check which parameters are required, and if the value are exceed the limitation, or you can set a default value if some optional key is not given.
 
 ## How to Use
+Assuming you have this json:
+~~~
+{
+    "name": "Matthew",
+    "age" : 17,
+    "married" : true,
+    "hobby" : ["music","sport"],
+    "major" : "cs",
+    "contact_info" : {
+        "tele" : 123456,
+        "city" : ""
+    } 
+}
+~~~
+
+* name is required
+* age is in 0-120 range, and required
+* married is required
+* hobby can specify more then 4
+* major can only be "cs" or "ee"
+* contact_info is optional
+* tele has a default value 1234
+* city has a default value "shanghai"
+
+
+Then you must have this struct to unmarshal the json, and check each of the parameter
+
+~~~
+type Person struct{
+    Name string     `json:"name"`
+    Age int         `json:"age"`
+    Married bool    `json:"married"`
+    Hobby []string  `json:"hobby"`
+    Major string    `json:"major"`
+    CI ContactInfo  `json:"contact_info"`
+}
+
+type ContactInfo struct{
+    Tele int    `json:"tele"`
+    City string `json:"city"`
+}
+~~~
+
+use this tool you can done all of this checking work in one line, define the struct like this:
+
+~~~
+type Person struct{
+    Name    string          `json:"name" is_required:"true"`
+    Age     *int            `json:"age" is_required:"true" min:"0" max:"120"`
+    Married *bool           `json:"married" is_required:"true"` 
+    Hobby   []string        `json:"hobby" max_len:"4"`
+    Major   string          `json:"major enum:"cs,ee""`
+    CI      *ContactInfo    `json:"contact_info"`
+}
+
+type ContactInfo struct{
+    Tele int    `json:"tele" default:"1234"`
+    City string `json:"city" default:"shanghai"`
+}
+~~~
+with all of this in hand, then run this:
+
+~~~
+p := Person{}
+body := `
+{
+    "name": "Matthew",
+    "age" : 17,
+    "married" : true,
+    "hobby" : ["music","sport"],
+    "major" : "cs",
+    "contact_info" : {
+        "tele" : 123456,
+        "city" : ""
+    } 
+}
+`
+err := ValidateJson([]byte(body), &p)
+fmt.Println(err)
+~~~
+
+Cool! Isn't it?
+
+## Note
+* int and bool are two special type, because int takes 0 as a default value when doing unmarshal, bool take a false as a default value, so we have no way to know if 0 is a caller specified value or default value, so we use pointer, if it those key is not given, then it will be a nil pointer
+
+* A embed struct must be define as a pointer, just like ContactInfo
+
+## Unsupport Case
+* set default value in array/slice is not support now, will supported later
+* nested link is not supported

example_test.go

@@ -0,0 +1,146 @@
+package validator
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type Person struct {
+	Name    string       `json:"name" is_required:"true"`
+	Age     *int         `json:"age" is_required:"true" min:"0" max:"120"`
+	Married *bool        `json:"married" is_required:"true"`
+	Hobby   []string     `json:"hobby" max_len:"4"`
+	Major   string       `json:"major" enum:"cs,ee"`
+	CI      *ContactInfo `json:"contact_info"`
+}
+
+type ContactInfo struct {
+	Tele int    `json:"tele" default:"1234"`
+	City string `json:"city" default:"shanghai"`
+}
+
+func TestExample(t *testing.T) {
+	p := Person{}
+	body := `
+	{
+		"name": "Matthew",
+		"age" : 17,
+		"married" : true,
+		"hobby" : ["music","sport"],
+		"major" : "cs",
+		"contact_info" : {
+			"city" : ""
+		} 
+	}
+	`
+	err := ValidateJson([]byte(body), &p)
+	fmt.Println(err)
+	fmt.Printf("%v\n", p)
+	fmt.Printf("%v\n", p.CI)
+}
+
+func TestExampleMissingRequired(t *testing.T) {
+	p := Person{}
+	body := `
+	{
+		"age" : 17,
+		"married" : true,
+		"hobby" : ["music","sport"],
+		"major" : "cs",
+		"contact_info" : {
+			"city" : ""
+		} 
+	}
+	`
+	err := ValidateJson([]byte(body), &p)
+	fmt.Println(err)
+	fmt.Printf("%v\n", p)
+	fmt.Printf("%v\n", p.CI)
+
+	assert.NotEmpty(t, err)
+}
+
+func TestExampleAgeExceed(t *testing.T) {
+	p := Person{}
+	body := `
+	{
+		"name": "Matthew",
+		"age" : 130,
+		"married" : true,
+		"hobby" : ["music","sport"],
+		"major" : "cs",
+		"contact_info" : {
+			"city" : ""
+		} 
+	}
+	`
+	err := ValidateJson([]byte(body), &p)
+	fmt.Println(err)
+	fmt.Printf("%v\n", p)
+	fmt.Printf("%v\n", p.CI)
+	assert.NotEmpty(t, err)
+}
+
+func TestExampleHobbyExceed4(t *testing.T) {
+	p := Person{}
+	body := `
+	{
+		"name": "Matthew",
+		"age" : 17,
+		"married" : true,
+		"hobby" : ["music","sport","1","2","5"],
+		"major" : "cs",
+		"contact_info" : {
+			"city" : ""
+		} 
+	}
+	`
+	err := ValidateJson([]byte(body), &p)
+	fmt.Println(err)
+	fmt.Printf("%v\n", p)
+	fmt.Printf("%v\n", p.CI)
+	assert.NotEmpty(t, err)
+}
+
+func TestExampleMajorNotInEnum(t *testing.T) {
+	p := Person{}
+	body := `
+	{
+		"name": "Matthew",
+		"age" : 17,
+		"married" : true,
+		"hobby" : ["music","sport"],
+		"major" : "csx",
+		"contact_info" : {
+			"city" : ""
+		} 
+	}
+	`
+	err := ValidateJson([]byte(body), &p)
+	fmt.Println(err)
+	fmt.Printf("%v\n", p)
+	fmt.Printf("%v\n", p.CI)
+	assert.NotEmpty(t, err)
+}
+
+func TestExampleEmptyCI(t *testing.T) {
+	p := Person{}
+	body := `
+	{
+		"name": "Matthew",
+		"age" : 17,
+		"married" : true,
+		"hobby" : ["music","sport"],
+		"major" : "cs"
+	}
+	`
+	err := ValidateJson([]byte(body), &p)
+	fmt.Println(err)
+	fmt.Printf("%v\n", p)
+	fmt.Printf("%v\n", p.CI)
+	assert.Empty(t, err)
+	assert.Equal(t, "shanghai", p.CI.City)
+	assert.Equal(t, 1234, p.CI.Tele)
+}

validator.go

@@ -12,6 +12,7 @@ import (
 // 1. int, bool 类型声明的时候必须用指针
 // 2. 如果是嵌入对象，那么必须是required，不然会panic
 // 4. 类似链表嵌套
+// set default value in array/slice is not support now
 
 func ValidateJson(in []byte, v interface{}) error {
 	err := json.Unmarshal(in, v)
@@ -126,13 +127,17 @@ func ValidateParameters(in interface{}) (err error) {
 		}
 
 		if maxLen, ok := sf.Tag.Lookup("max_len"); ok {
+			maxLenInt, _ := strconv.Atoi(maxLen)
 			switch sf.Type.Kind() {
 			case reflect.String:
-				maxLenInt, _ := strconv.Atoi(maxLen)
 				s := sv.String()
 				if len(s) > maxLenInt {
 					return fmt.Errorf("%s exceed the max len %d", sf.Name, maxLenInt)
 				}
+			case reflect.Slice, reflect.Array:
+				if sv.Len() > maxLenInt {
+					return fmt.Errorf("%s exceed the max len %d", sf.Name, maxLenInt)
+				}
 			}
 		}