1. 应用场景

代币系统需要支持新种类代币发行、代币转账，额度查询，代币增发，代币回收、账户冻结，锁仓等功能。
代币增发后转入coinbase账户，coinbase账户与普通账户之间可以互相转账。这样就实现了代币流通。

2. 数据的生命周期

代币（token）数据内容包括代币简称、代币名称、代币发行者、总供应量、锁仓标识等信息；
账户（account）数据内容包括账户名、账户的代币类型、冻结标识、余额等信息。

代币发行方可以发行代币、增发代币、回收代币、锁仓、冻结账户；
用户可以将代币转账从自己的账户给别人的账户。

3. 数据结构

• token的key为：

TokenSymbol 

• token的value结构为：

type Token struct {  TokenSymbol string `json:"TokenSymbol"`  TokenName   string `json:"TokenName"`  Owner       string `json:"Owner"`  TotalSupply int64 `json:"TotalSupply"`  Lock        bool `json:"Lock"` } 

• account采用复合key的结构，包含账户名、代币信息，这样每种代币就有了单独的账户体系：

accountKey, err := stub.CreateCompositeKey("account", []string{accountName, symbol}) 

可以根据key值前缀进行范围查询，查询出账户名拥有的各种代币。

• account的value结构为：

type Account struct {  AccountName string `json:"AccountName"`  TokenSymbol string `json:"TokenSymbol"`  Frozen      bool `json:"Frozen"`  Balance     int64 `json:"Balance"` } 

4. 合约源码

package main  import ( "encoding/json" "errors" "fmt" "strconv" "github.com/hyperledger/fabric-chaincode-go/shim"  pb "github.com/hyperledger/fabric-protos-go/peer" ) // Token 代币数据 type Token struct {  TokenSymbol string `json:"TokenSymbol"`  TokenName   string `json:"TokenName"`  Owner       string `json:"Owner"`  TotalSupply int64 `json:"TotalSupply"`  Lock        bool `json:"Lock"` } // Account 代币账户数据 type Account struct {  AccountName string `json:"AccountName"`  TokenSymbol string `json:"TokenSymbol"`  Frozen      bool `json:"Frozen"`  Balance     int64 `json:"Balance"` } func (token *Token) transfer(from *Account, to *Account, amount int64) error { if token.Lock { return errors.New("锁仓状态，无法转账") } if from.Frozen { return errors.New("From 账户已被冻结") } if to.Frozen { return errors.New("To 账户已被冻结") } if from.Balance >= amount {   from.Balance -= amount   to.Balance += amount  } else { return errors.New("From 账户余额不足") } return nil } func (token *Token) mint(amount int64, account *Account) error { if token.Lock { return errors.New("锁仓状态，无法增发代币") }  token.TotalSupply += amount  account.Balance += amount  return nil } func (token *Token) burn(amount int64, account *Account) error { if token.Lock { return errors.New("锁仓状态，无法回收代币") } if account.Balance >= amount {   account.Balance -= amount   token.TotalSupply -= amount  } return nil } func (token *Token) setLock(lock bool) {  token.Lock = lock } func (account *Account) setFrozen(status bool) {  account.Frozen = status } func (account *Account) balance() int64 { return account.Balance } // Contract ... type Contract struct { } // Init ... func (tc *Contract) Init(stub shim.ChaincodeStubInterface) pb.Response { return shim.Success(nil) } // Invoke ... func (tc *Contract) Invoke(stub shim.ChaincodeStubInterface) pb.Response {  functions, args := stub.GetFunctionAndParameters() if functions == "issueNewToken" { return tc.issueNewToken(stub, args) } else if functions == "mintToken" { return tc.mintToken(stub, args) } else if functions == "burnToken" { return tc.burnToken(stub, args) } else if functions == "transferToken" { return tc.transferToken(stub, args) } else if functions == "setLock" { return tc.setLock(stub, args) } else if functions == "frozenAccount" { return tc.frozenAccount(stub, args) } else if functions == "queryToken" { return tc.queryToken(stub, args) } else if functions == "queryAccount" { return tc.queryAccount(stub, args) } return shim.Error("Invalid function name in Contract.") } func (tc *Contract) issueNewToken(stub shim.ChaincodeStubInterface, args []string) pb.Response { if len(args) != 3 { return shim.Error("Incorrect number of arguments. Expecting 3") }   tokenSymbol := args[0]  tokenName := args[1]  supply, err := strconv.ParseInt(args[2], 10, 64) if err != nil { return shim.Error(err.Error()) } // 判断token是否已存在  exist, err := stub.GetState(tokenSymbol) if exist != nil { return shim.Error("Token existed!") }   token := &Token{   TokenSymbol: tokenSymbol,   TokenName:   tokenName,   Owner: "coinbase",   TotalSupply: supply,   Lock: false, }   account := Account{   AccountName: token.Owner,   TokenSymbol: tokenSymbol,   Frozen: false,   Balance:     supply, }   tokenAsBytes, err := json.Marshal(token) if err != nil { return shim.Error(err.Error()) }   err = stub.PutState(tokenSymbol, tokenAsBytes) if err != nil { return shim.Error(err.Error()) }   accountKey, err := stub.CreateCompositeKey("account", []string{token.Owner, tokenSymbol}) if err != nil { return shim.Error(err.Error()) }  acountAsBytes, err := json.Marshal(account) if err != nil { return shim.Error(err.Error()) }   err = stub.PutState(accountKey, acountAsBytes) if err != nil { return shim.Error(err.Error()) } return shim.Success(nil) } func (tc *Contract) mintToken(stub shim.ChaincodeStubInterface, args []string) pb.Response { if len(args) != 2 { return shim.Error("Incorrect number of arguments. Expecting 2.") }  symbol := args[0]  amount, err := strconv.ParseInt(args[1], 10, 64) if err != nil { return shim.Error(err.Error()) }   tokenAsBytes, err := stub.GetState(symbol) if err != nil { return shim.Error(err.Error()) } if tokenAsBytes == nil { return shim.Error("Entity not found") }  token := Token{}  err = json.Unmarshal(tokenAsBytes, &token) if err != nil { return shim.Error("{"Error":"Failed to decode JSON of: " + symbol + ""}") }   accountKey, err := stub.CreateCompositeKey("account", []string{token.Owner, symbol}) if err != nil { return shim.Error(err.Error()) }  accountAsBytes, err := stub.GetState(accountKey) if err != nil { return shim.Error(err.Error()) } if accountAsBytes == nil { return shim.Error("Entity not found") }  account := Account{}  err = json.Unmarshal(accountAsBytes, &account) if err != nil { return shim.Error("{"Error":"Failed to decode JSON of: " + token.Owner + symbol + ""}") }   err = token.mint(amount, &account) if err != nil { return shim.Error(err.Error()) }   tokenAsBytes, err = json.Marshal(token) if err != nil { return shim.Error(err.Error()) }   err = stub.PutState(symbol, tokenAsBytes) if err != nil { return shim.Error(err.Error()) }   accountAsBytes, err = json.Marshal(account) if err != nil { return shim.Error(err.Error()) }   err = stub.PutState(accountKey, accountAsBytes) if err != nil { return shim.Error(err.Error()) } return shim.Success(nil) } func (tc *Contract) burnToken(stub shim.ChaincodeStubInterface, args []string) pb.Response { if len(args) != 3 { return shim.Error("Incorrect number of arguments. Expecting 3.") }   symbol := args[0]  amount, err := strconv.ParseInt(args[1], 10, 64) if err != nil { return shim.Error(err.Error()) }  accountName := args[2]   tokenAsBytes, err := stub.GetState(symbol) if err != nil { return shim.Error(err.Error()) } if tokenAsBytes == nil { return shim.Error("Entity not found") }   token := Token{}  err = json.Unmarshal(tokenAsBytes, &token) if err != nil { return shim.Error("{"Error":"Failed to decode JSON of: " + symbol + ""}") }   accountKey, err := stub.CreateCompositeKey("account", []string{accountName, symbol}) if err != nil { return shim.Error(err.Error()) }   accountAsBytes, err := stub.GetState(accountKey) if err != nil { return shim.Error(err.Error()) } if accountAsBytes == nil { return shim.Error("Entity not found") }   account := Account{}  err = json.Unmarshal(accountAsBytes, &account) if err != nil { return shim.Error("{"Error":"Failed to decode JSON of: " + accountName + symbol + ""}") }   err = token.burn(amount, &account) if err != nil { return shim.Error(err.Error()) }   tokenAsBytes, err = json.Marshal(token) if err != nil { return shim.Error(err.Error()) }   err = stub.PutState(symbol, tokenAsBytes) if err != nil { return shim.Error(err.Error()) }   accountAsBytes, err = json.Marshal(account) if err != nil { return shim.Error(err.Error()) }   err = stub.PutState(accountKey, accountAsBytes) if err != nil { return shim.Error(err.Error()) } return shim.Success(nil) } func (tc *Contract) transferToken(stub shim.ChaincodeStubInterface, args []string) pb.Response {  symbol := args[0]  from := args[1]  to := args[2]  amount, err := strconv.ParseInt(args[3], 10, 64) if err != nil { return shim.Error(err.Error()) } if amount <= 0 { return shim.Error("Incorrect amount!") } // 源账户处理  fromKey, err := stub.CreateCompositeKey("account", []string{from, symbol}) if err != nil { return shim.Error(err.Error()) }  fromAsBytes, err := stub.GetState(fromKey) if err != nil { return shim.Error(err.Error()) } if fromAsBytes == nil { return shim.Error("Entity not found") }   fromAccount := Account{}  err = json.Unmarshal(fromAsBytes, &fromAccount) if err != nil { return shim.Error("{"Error":"Failed to decode JSON of: " + from + symbol + ""}") } // 目的账户处理  toKey, err := stub.CreateCompositeKey("account", []string{to, symbol}) if err != nil { return shim.Error(err.Error()) }  toAsBytes, err := stub.GetState(toKey) if err != nil { return shim.Error(err.Error()) }   toAccount := Account{} if toAsBytes == nil {   toAccount.AccountName = to   toAccount.Balance = 0   toAccount.Frozen = false   toAccount.TokenSymbol = symbol  } else {   err = json.Unmarshal(toAsBytes, &toAccount) if err != nil { return shim.Error("{"Error":"Failed to decode JSON of: " + to + symbol + ""}") } } // token处理  tokenAsBytes, err := stub.GetState(symbol) if err != nil { return shim.Error(err.Error()) } if tokenAsBytes == nil { return shim.Error("Entity not found") }   token := &Token{}  err = json.Unmarshal(tokenAsBytes, &token) if err != nil { return shim.Error("{"Error":"Failed to decode JSON of: " + symbol + ""}") } // 转账  err = token.transfer(&fromAccount, &toAccount, amount) if err != nil { return shim.Error(err.Error()) } // 入库  fromAsBytes, err = json.Marshal(fromAccount) if err != nil { return shim.Error(err.Error()) }  err = stub.PutState(fromKey, fromAsBytes) if err != nil { return shim.Error(err.Error()) }   toAsBytes, err = json.Marshal(toAccount) if err != nil { return shim.Error(err.Error()) }  err = stub.PutState(toKey, toAsBytes) if err != nil { return shim.Error(err.Error()) } return shim.Success(nil) } func (tc *Contract) setLock(stub shim.ChaincodeStubInterface, args []string) pb.Response { if len(args) != 2 { return shim.Error("Incorrect number of arguments. Expecting 2") }   symbol := args[0]  lock, err := strconv.ParseBool(args[1]) if err != nil { return shim.Error(err.Error()) }   tokenAsBytes, err := stub.GetState(symbol) if err != nil { return shim.Error(err.Error()) } if tokenAsBytes == nil { return shim.Error("Entity not found") }   token := Token{}  err = json.Unmarshal(tokenAsBytes, &token) if err != nil { return shim.Error("{"Error":"Failed to decode JSON of: " + symbol + ""}") }   token.setLock(lock)   tokenAsBytes, _ = json.Marshal(token)  err = stub.PutState(symbol, tokenAsBytes) if err != nil { return shim.Error(err.Error()) } return shim.Success(nil) } func (tc *Contract) frozenAccount(stub shim.ChaincodeStubInterface, args []string) pb.Response { if len(args) != 3 { return shim.Error("Incorrect number of arguments. Expecting 3") }  symbol := args[0]  accountName := args[1]  frozen, err := strconv.ParseBool(args[2]) if err != nil { return shim.Error(err.Error()) }   accountKey, err := stub.CreateCompositeKey("account", []string{accountName, symbol}) if err != nil { return shim.Error(err.Error()) }   accountAsBytes, err := stub.GetState(accountKey) if err != nil { return shim.Error(err.Error()) } if accountAsBytes == nil { return shim.Error("Entity not found") }   account := Account{}  err = json.Unmarshal(accountAsBytes, &account) if err != nil { return shim.Error("{"Error":"Failed to decode JSON of: " + accountName + symbol + ""}") }   account.setFrozen(frozen)   accountAsBytes, _ = json.Marshal(account)  err = stub.PutState(accountKey, accountAsBytes) if err != nil { return shim.Error(err.Error()) } return shim.Success(nil) } func (tc *Contract) queryToken(stub shim.ChaincodeStubInterface, args []string) pb.Response { if len(args) != 1 { return shim.Error("Incorrect number of arguments. Expecting 1") }  symbol := args[0]   tokenAsBytes, err := stub.GetState(symbol) if err != nil { return shim.Error(err.Error()) } if tokenAsBytes == nil { return shim.Error("{"Error":"Nil value for " + symbol + ""}") }  fmt.Printf("Query Response:%sn", string(tokenAsBytes)) return shim.Success(tokenAsBytes) } func (tc *Contract) queryAccount(stub shim.ChaincodeStubInterface, args []string) pb.Response { if len(args) != 2 { return shim.Error("Incorrect number of arguments. Expecting 2") }   accountName := args[0]  symbol := args[1]  accountKey, err := stub.CreateCompositeKey("account", []string{accountName, symbol}) if err != nil { return shim.Error(err.Error()) }   accountAsBytes, err := stub.GetState(accountKey) if err != nil { return shim.Error(err.Error()) } if accountAsBytes == nil { return shim.Error("{"Error":"Nil value for " + accountName + symbol + ""}") }  fmt.Printf("Query Response:%sn", string(accountAsBytes)) return shim.Success(accountAsBytes) } func main() {  err := shim.Start(new(Contract)) if err != nil {   fmt.Printf("Error starting Contract chaincode: %s", err) } } 

参考：
https://www.netkiller.cn/blockchain/hyperledger/chaincode/chaincode.example.html#chaincode.token