SINGLE NODE BLOCKCHAIN WITH REST EXAMPLE

A simple single node sha256 blockchain with a REST JSON API (to view (GET) the blockchain and add (POST) a block).

Table of Contents

• PREREQUISITES
• OVERVIEW
• RUN
  • GET (View the entire Blockchain)
  • GET (Show a Particular Block)
  • POST (Add a Block)
• HOW IT WORKS

Documentation and Reference

• Refer to my simple-webserver-with-REST for the webserver engine
• Refer to my cheat sheet on blockchains
• I got a lot of inspiration from here

PREREQUISITES

Gorilla/mux is a popular router I use for the webserver.

go get -v -u github.com/gorilla/mux

OVERVIEW

This code is broken up into three parts,

• guts The blockchain code
• blockchain-interface The interface to the blockchain
• Webserver The API and gui

This examples will,

• Create a Blockchain
• Hash a Block
• View the Entire Blockchain via a web GUI
• View a specific Block via a REST API
• Add a Block (with your data) to the chain via a REST API

This illustration may help,

RUN

go run single-node-blockchain-with-REST.go \
       guts.go blockchain.go blockchain-interface.go \
       router.go routes.go handlers.go logger.go

GET (View the entire Blockchain)

Then you can goto the webpage to see your first block,

localhost:1234/

You could also use curl from the command line,

curl localhost:1234

GET (Show a Particular Block)

localhost:1234//showblock/0

curl localhost:1234/showblock/0

POST (Add a Block)

curl -H "Content-Type: application/json" \
     -X POST \
     -d '{"data":"Add this data for new block"}' \
     localhost:1234/addblock

Check,

localhost:1234/

HOW IT WORKS

We will just be looking at the guts, ignoring the webserver and blockchain-interface.

So it actually becomes quite simple. A Block is just a struct and The Blockchain is simply a slice of structs. That's it.

type BlockStruct struct {
    Index     int    `json:"index"`
    Timestamp string `json:"timestamp"`
    Data      string `json:"data"`
    Hash      string `json:"hash"`
    PrevHash  string `json:"prevhash"`
}

type BlockchainSlice []BlockStruct

var Blockchain = BlockchainSlice{}

And guts.go contain the three basic things you want to do to that Blockchain (slice of structs),

• calculateBlockHash()
• isBlockValid()
• createNewBlock()