Getting Started

Learn how to validate JSON HTTP requests using reusable schemas, typed validation fields, and structured validation rules with the NLG Form package.

The example below demonstrates a complete validation workflow using:

HTTP request binding
Typed validation schemas
Reusable validation rules
JSON request validation
Structured request processing

The incoming request is a standard HTTP POST request with a JSON payload:

{
  "name": "abcdefd",
  "age": 10
}

The validation flow consists of:

Defining a request structure
Creating reusable typed form fields
Building validation rules
Binding and validating the HTTP request
Returning structured JSON responses

Create the Request Schema

The schema defines reusable typed fields and validation rules for the incoming request.

Schemas are typically defined through functions instead of global variables to keep validation definitions immutable and isolated between application components.

package main

import (
	"github.com/netlifeguru/form"
	"github.com/netlifeguru/form/rules"
)

type PostRequest struct {
	Name string `json:"name"`
	Age  int    `json:"age"`
}

func PostSchema() form.Schema[PostRequest] {
	var PostForm = struct {
		Name form.StringField[PostRequest]
		Age  form.IntField[PostRequest]
	}{
		Name: form.Str[PostRequest]("name", func(r *PostRequest) string {
			return r.Name
		}),
		Age: form.Int[PostRequest]("age", func(r *PostRequest) int {
			return r.Age
		}),
	}

	var NameSchema = form.Schema[PostRequest]{
		rules.Required(PostForm.Name),
		rules.MinLen(PostForm.Name, 5),
	}

	var AgeSchema = form.Schema[PostRequest]{
		rules.RequiredInt(PostForm.Age),
		rules.Min(PostForm.Age, 8),
	}

	return form.Rules(
		NameSchema,
		AgeSchema,
	)
}

Create the HTTP Server

The HTTP handler binds the incoming JSON request into the PostRequest structure and validates it using the schema.

package main

import (
	"encoding/json"
	"fmt"
	"log/slog"
	"net/http"
	"os"

	"github.com/netlifeguru/form"
	"github.com/netlifeguru/form/httpform"
	"github.com/netlifeguru/router"
)

func main() {
	r := router.New()

	r.HandleFunc("/", "POST", func(w http.ResponseWriter, r *http.Request, ctx *router.Context) {
		var in PostRequest

		if !httpform.BindAndValidate(w, r, &in, PostSchema(), 1<<20) {
			fmt.Println("form validation failed")
			return
		}

		fmt.Println("request received:", in)

		w.Header().Set("Content-Type", "application/json")

		_ = json.NewEncoder(w).Encode(map[string]any{
			"message": "request received",
			"data":    in,
		})
	})

	form.SendTestPost(":8080/", map[string]any{
		"name": "abcdefd",
		"age":  10,
	})

	if err := r.ListenAndServe(8080); err != nil {
		slog.Error("failed to start server", "error", err)
		os.Exit(1)
	}
}

Note

The example uses the helper method:
form.SendTestPost(":8080/", map[string]any{
    "name": "abcdefd",
    "age":  10,
})
to automatically send a test HTTP POST request to the local server after startup.

This helper exists only to make the example self-contained and immediately runnable without requiring external tools such as curl or Postman.

Run the Application

Start the application:

go run .

The server starts on:

http://localhost:8080

Example Response

Successful validation returns a structured JSON response:

{
  "message": "request received",
  "data": {
    "name": "abcdefd",
    "age": 10
  }
}

If validation fails, the package automatically generates structured validation error responses through the httpform module.

Continue with the next sections to learn about validation rules, optional fields, conditional validation, custom error messages, schema composition, and advanced HTTP request processing.

The example below demonstrates a complete validation workflow using:

HTTP request binding
Typed validation schemas
Reusable validation rules
JSON request validation
Structured request processing

The incoming request is a standard HTTP POST request with a JSON payload:

{
  "name": "abcdefd",
  "age": 10
}

The validation flow consists of:

Defining a request structure
Creating reusable typed form fields
Building validation rules
Binding and validating the HTTP request
Returning structured JSON responses

Create the Request Schema

The schema defines reusable typed fields and validation rules for the incoming request.

Schemas are typically defined through functions instead of global variables to keep validation definitions immutable and isolated between application components.

package main

import (
	"github.com/netlifeguru/form"
	"github.com/netlifeguru/form/rules"
)

type PostRequest struct {
	Name string `json:"name"`
	Age  int    `json:"age"`
}

func PostSchema() form.Schema[PostRequest] {
	var PostForm = struct {
		Name form.StringField[PostRequest]
		Age  form.IntField[PostRequest]
	}{
		Name: form.Str[PostRequest]("name", func(r *PostRequest) string {
			return r.Name
		}),
		Age: form.Int[PostRequest]("age", func(r *PostRequest) int {
			return r.Age
		}),
	}

	var NameSchema = form.Schema[PostRequest]{
		rules.Required(PostForm.Name),
		rules.MinLen(PostForm.Name, 5),
	}

	var AgeSchema = form.Schema[PostRequest]{
		rules.RequiredInt(PostForm.Age),
		rules.Min(PostForm.Age, 8),
	}

	return form.Rules(
		NameSchema,
		AgeSchema,
	)
}

Create the HTTP Server

The HTTP handler binds the incoming JSON request into the PostRequest structure and validates it using the schema.

package main

import (
	"encoding/json"
	"fmt"
	"log/slog"
	"net/http"
	"os"

	"github.com/netlifeguru/form"
	"github.com/netlifeguru/form/httpform"
	"github.com/netlifeguru/router"
)

func main() {
	r := router.New()

	r.HandleFunc("/", "POST", func(w http.ResponseWriter, r *http.Request, ctx *router.Context) {
		var in PostRequest

		if !httpform.BindAndValidate(w, r, &in, PostSchema(), 1<<20) {
			fmt.Println("form validation failed")
			return
		}

		fmt.Println("request received:", in)

		w.Header().Set("Content-Type", "application/json")

		_ = json.NewEncoder(w).Encode(map[string]any{
			"message": "request received",
			"data":    in,
		})
	})

	form.SendTestPost(":8080/", map[string]any{
		"name": "abcdefd",
		"age":  10,
	})

	if err := r.ListenAndServe(8080); err != nil {
		slog.Error("failed to start server", "error", err)
		os.Exit(1)
	}
}

Note

The example uses the helper method:
form.SendTestPost(":8080/", map[string]any{
    "name": "abcdefd",
    "age":  10,
})
to automatically send a test HTTP POST request to the local server after startup.

This helper exists only to make the example self-contained and immediately runnable without requiring external tools such as curl or Postman.

Run the Application

Start the application:

go run .

The server starts on:

http://localhost:8080

Example Response

Successful validation returns a structured JSON response:

{
  "message": "request received",
  "data": {
    "name": "abcdefd",
    "age": 10
  }
}

If validation fails, the package automatically generates structured validation error responses through the httpform module.

Continue with the next sections to learn about validation rules, optional fields, conditional validation, custom error messages, schema composition, and advanced HTTP request processing.

Getting Started

Create the Request Schema

Create the HTTP Server

Run the Application

Example Response

On this page

Getting Started

Create the Request Schema

Create the HTTP Server

Run the Application

Example Response

On this page