Hyperledger Fabric Chaincode Examples: Notarization, Asset Transfer, Digital Currency, Diploma Verification, Energy Sharing, and Logistics

Chaincode Example 1: Information Notarization

Overview

The Go file chaincode_example01.go implements a simple key‑value store that can be initialized, read, and modified on the ledger.

Main Functions

read : read the value of a given key.

write : create or modify a key’s value.

init : initialize the key hello_world .

invoke : dispatch to init or write based on arguments.

query : call read to retrieve a value.

Execution Flow

The main function starts the chaincode by calling shim.Start . The three core functions init , invoke , and query use stub.PutState and stub.GetState to interact with the ledger.

REST API Interaction

Deployment and invocation are performed via JSON‑RPC requests. Example deployment payload:

{
  "jsonrpc": "2.0",
  "method": "deploy",
  "params": {
    "type": 1,
    "chaincodeID": {"path": "https://github.com/ibm-blockchain/learn-chaincode/finished"},
    "ctorMsg": {"function": "init", "args": ["hi there"]},
    "secureContext": "jim"
  },
  "id": 1
}

Invocation payload example:

{
  "jsonrpc": "2.0",
  "method": "invoke",
  "params": {
    "type": 1,
    "chaincodeID": {"name": "
chaincode‑hash
"},
    "ctorMsg": {"function": "init", "args": ["swb"]},
    "secureContext": "jim"
  },
  "id": 2
}

Chaincode Example 2: Asset Trading

Overview

The Go file chaincode_example02.go demonstrates initializing two accounts (A and B), transferring assets between them, querying balances, and deleting accounts.

Main Functions

init : create accounts A and B with initial balances.

invoke : perform a transfer between A and B.

query : retrieve the balance of a specified account.

delete : remove an account.

Dependencies

import (
    "errors"
    "fmt"
    "strconv"
    "github.com/hyperledger/fabric/core/chaincode/shim"
)

Conversion between strings and integers is handled by strconv . The transfer logic adjusts balances based on the sign of the amount.

Digital Currency Issuance and Management

Overview

This smart contract models a simple commercial scenario with three roles: a central bank, commercial banks, and enterprises. The central bank can issue currency, banks can receive allocations, and enterprises can transfer digital coins.

Main Functions

init : set up the central bank and initial supply.

invoke : route to internal functions.

query : read state data.

createBank , createCompany : add banks or enterprises.

issueCoin , issueCoinToBank , issueCoinToCp : issue or allocate coins.

transfer : move coins between enterprises.

Various get* functions to retrieve banks, companies, transactions, and individual records.

write* functions to persist updated entities.

Data Model

CenterBank: Name, TotalNumber, RestNumber, ID (fixed 0).

Bank: Name, TotalNumber, RestNumber, ID.

Company: Name, Number, ID.

Transaction: FromType, FromID, ToType, ToID, Time, Number, ID.

Diploma Certification

Overview

The contract enables a simple credential management system where schools issue diplomas to individuals, and verification agencies can query them. Records are immutable on the blockchain, and schools can update or revoke diplomas.

Data Model

School: Name, Location, Address, PublicKey, PrivateKey, StudentList.

Student: Name, Address, PastDiplomas.

DiplomaInfo: ID, School, StartYear, EndYear, Status (0‑graduated, 1‑dropped).

Record: ID, SchoolAddress, SchoolSignature, StudentAddress, Timestamp, Operation (0‑graduate, 1‑drop, 2‑enroll).

Key Functions

init , invoke , query .

updateDiploma : school updates a student’s diploma status.

enrollStudent : school adds a new student.

createSchool , createStudent : add new entities.

Various get* functions to retrieve schools, students, diplomas, and records.

write* functions to persist changes.

Community Energy Sharing

Overview

This contract models a micro‑grid where households can produce solar energy and trade excess electricity with neighbors using a blockchain‑based marketplace.

Data Model

Household: Address, RemainingEnergy, Balance, ID, Status (0‑inactive, 1‑active), PublicKey, PrivateKey.

Transaction: BuyerAddress, SellerAddress, EnergyAmount, AmountPaid, ID, Timestamp.

Key Functions

init , invoke , query .

createUser : register a new household.

buyByAddress : purchase energy from another household.

getTransactionById , getTransactions , getHomes , getHomeByAddress , changeStatus , writeUser , writeTransaction .

Logistics Supply Chain Simple Case

Overview

The contract implements a basic logistics application where a single logistics company, multiple senders, and multiple receivers interact to create, update, and finalize shipping orders on the blockchain.

Data Model

ExpressOrder: ID, SenderAddress, ReceiverAddress, SenderContact, ReceiverContact, Fee, FeePayType (0‑sender, 1‑receiver), PrepaidFee, DeliveryInfo, ReceiverSignature.

Sender / Receiver: Name, Address, AccountAddress, PublicKey, PrivateKey (receiver), Contact, Balance.

LogisticsCompany: Name, Address, Contact, PublicKey, PrivateKey, Balance, List of ExpressPoints.

ExpressPoint: Name, Location, Contact, PublicKey, PrivateKey, AccountAddress.

Key Functions

init , invoke , query .

createUser , createExpress , createExpressPoint , createExpressOrder , finishExpressOrder , addExpressPointer , updateExpressOrder .

Query functions: getExpressOrderById , getExpress , getUserByAddress , getExpressPointByAddress .

Write functions: writeExpress , writeExpressOrder , writeUser , writeExpressPoint .

REST API Examples

All operations are invoked via JSON‑RPC with method set to deploy , invoke , or query and appropriate ctorMsg arguments as shown in the earlier examples.