Simple JSON HTML Example

NetBurner Simple JSON HTML Example

An example application demonstrating various methods for generating JSON responses from a NetBurner embedded web server.

Overview

This application showcases multiple approaches to serve JSON data from a NetBurner device, including static files, dynamic generation, and configuration-based responses. It provides a practical reference for developers working with NetBurner's web capabilities.

Shows several methods to have a NetBurner respond to web requests with JSON objects:

• Respond and generate the text directly.
• Respond and generate the response with a JSON lever object.
• Respond and generate the response using configuration variables.
• Respond and generate the response using a pre-built page stored in with web pages and using the dynamic web page capabilities.

Features

The application demonstrates several JSON response methods:

1. Static JSON Files

• plain.json: Pre-formatted static JSON content
• Simple text-based JSON stored as a file

2. Variable-Based Dynamic JSON

• ut.json: Template-based JSON with embedded variables
• Uses NetBurner's variable substitution system
• Displays runtime information like uptime, build date/time, and NNDK version

3. Callback-Based Dynamic JSON

• callback.json: Uses C++ callback functions to generate JSON
• Demonstrates the <!--CPPCALL DoGeneerateJson --> mechanism
• Generates JSON content programmatically at request time

4. Function-Based JSON Responses

• GetJson: Direct HTTP callback without associated HTML file
• GetLexerJson: Uses NetBurner's JSON lexer for structured generation
• Provides complete HTTP response handling in C++ code

5. Configuration System Integration

• Config: Exposes the entire configuration tree as JSON
• Config/AppData/MyOwnValue: Access specific configuration values
• Requires enabling the configuration mirror

File Structure

/
    main.cpp           # Main application code
    htmlvar.h          # Variable declarations for web pages
    index.html         # Main navigation page
    plain.json         # Static JSON example
    ut.json            # Variable-based JSON template
    callback.json      # Callback-based JSON page

Key Components

Main Application (main.cpp)

• Initializes network stack and HTTP server
• Defines global variables for web page access
• Implements callback functions for dynamic JSON generation
• Sets up configuration system integration

JSON Generation Methods

Method 1: Direct Text Output

int BuildAJsonResponseByText(int sock, HTTP_Request &pd)
{
    writestring(sock, "HTTP/1.0 200 OK\r\nPragma: no-cache\r\nContent-Type: application/json\r\n\r\n");
    writestring(sock, "{\"Test\":\"Json\"}");
    return 1;
}

Method 2: JSON Lexer

int BuildAJsonResponseByLexer(int sock, HTTP_Request &pd)
{
    ParsedJsonDataSet pjs;
    pjs.StartBuilding();
    pjs.Add("ANumber", 1234);
    pjs.Add("AString", "Testing123");
    pjs.AddMyMac("MyMacAddress");
    pjs.DoneBuilding();
    pjs.PrintObjectToFd(sock, true);
    return 1;
}

Method 3: Callback Function

void DoGeneerateJson(int sock, PCSTR url)
{
    fdprintf(sock, "{\r\n\"Generated\":\"ByCallback\",\r\n");
    fdprintf(sock, "\"Uptime\":%ld\r\n}", Secs);
}

Usage

1. Build and Deploy: Compile the application and deploy to your NetBurner device
2. Access Web Interface: Navigate to your device's IP address (default port 80)
3. Test JSON Endpoints: Use the provided links to test different JSON generation methods

Example URLs

Assuming your device IP is 10.1.2.3:

• http://10.1.2.3/ - Main navigation page
• http://10.1.2.3/plain.json - Static JSON
• http://10.1.2.3/ut.json - Variable-based JSON
• http://10.1.2.3/callback.json - Callback-generated JSON
• http://10.1.2.3/GetJson - Direct function response
• http://10.1.2.3/GetLexerJson - JSON lexer response
• http://10.1.2.3/Config - Full configuration tree
• http://10.1.2.3/Config/AppData/MyOwnValue - Specific config value

Configuration

The application includes a configuration variable example:

config_int gMyOwnVal{appdata, 199, "MyOwnValue"};

This demonstrates how to expose application-specific configuration data through the web interface.

Build Requirements

• NetBurner NNDK (NetBurner Network Development Kit)
• C++ compiler with NetBurner libraries
• Standard NetBurner build environment

Key Features Demonstrated

• HTTP server initialization and setup
• Multiple JSON response generation techniques
• Variable substitution in web pages
• Callback-based dynamic content generation
• Configuration system integration
• Proper HTTP header handling
• Network stack initialization

Notes

• The application enables system diagnostics (should be removed for production)
• Configuration mirror must be enabled for config-based endpoints
• Default HTTP port is 80
• Application waits for active network connection before proceeding

Learning Objectives

This example is ideal for developers who want to understand:

• NetBurner web server capabilities
• JSON API development on embedded systems
• Dynamic content generation techniques
• Configuration system integration
• HTTP request handling in embedded C++