fabric鍊碼要實作兩個方法：init 和 invoke
init用來執行個體化鍊碼，invoke用來調用方法
示例代碼可以在github上搜尋fabric-samples，找到你想要的版本下載下傳，這裡用1.4版本的做示例
進入chaincode目錄
我們就來看最基礎的實作了賬戶兩兩轉賬的鍊碼chaincode_example02
裡面有node版本go版本和java版本
我們分析java版本
點開目錄，發現這個鍊碼是一個grandle項目
我們分析一下它的配置
我們也可以用Maven來建構這個項目，這裡不加贅述
//項目需要的依賴
dependencies {
compile group: 'org.hyperledger.fabric-chaincode-java', name: 'fabric-chaincode-shim', version: '1.+'
testCompile group: 'junit', name: 'junit', version: '4.12'
}
shadowJar {
baseName = 'chaincode'
version = null
classifier = null
打包時将org.hyperledger.fabric.example.SimpleChaincode設定為Main-Class
manifest {
attributes 'Main-Class': 'org.hyperledger.fabric.example.SimpleChaincode'
}
}
我們來看init方法
//執行個體化Log對象
private static Log _logger = LogFactory.getLog(SimpleChaincode.class);
@Override
//傳入一個ChaincodeStub對象，對象中有方法名，和方法參數
public Response init(ChaincodeStub stub) {
try {
_logger.info("Init java simple chaincode");
//擷取使用的方法名
String func = stub.getFunction();
//如果不是init方法
if (!func.equals("init")) {
return newErrorResponse("function other than init is not supported");
}
//擷取方法參數
List<String> args = stub.getParameters();
if (args.size() != 4) {
newErrorResponse("Incorrect number of arguments. Expecting 4");
}
// Initialize the chaincode
//取出4個參數中的兩個賬戶，2個初始金額
String account1Key = args.get(0);
int account1Value = Integer.parseInt(args.get(1));
String account2Key = args.get(2);
int account2Value = Integer.parseInt(args.get(3));
_logger.info(String.format("account %s, value = %s; account %s, value %s", account1Key, account1Value, account2Key, account2Value));
//将賬戶狀态到鍊上
stub.putStringState(account1Key, args.get(1));
stub.putStringState(account2Key, args.get(3));
return newSuccessResponse();
} catch (Throwable e) {
return newErrorResponse(e);
}
}
這個init方法接收4個參數，賬戶1和他賬戶上的錢，賬戶2和他賬戶上的錢，存傳入連結上，我們可以修改這個方法，用來初始化我們的賬本
invoke方法
//invoke方法負責調用其他查詢或操作賬本上資料的方法：invoke,delete,query
@Override
public Response invoke(ChaincodeStub stub) {
try {
_logger.info("Invoke java simple chaincode");
String func = stub.getFunction();
List<String> params = stub.getParameters();
if (func.equals("invoke")) {
return invoke(stub, params);
}
if (func.equals("delete")) {
return delete(stub, params);
}
if (func.equals("query")) {
return query(stub, params);
}
return newErrorResponse("Invalid invoke function name. Expecting one of: [\"invoke\", \"delete\", \"query\"]");
} catch (Throwable e) {
return newErrorResponse(e);
}
}
第二個invoke方法，這個invoke方法執行賬戶之間的轉賬操作，由上一級invoke把stub和參數傳進來，分析參數是否符合條件，然後完成轉帳更新資料
//接收一個stub對象和若幹參數
private Response invoke(ChaincodeStub stub, List<String> args) {
if (args.size() != 3) {
return newErrorResponse("Incorrect number of arguments. Expecting 3");
}
//取得轉賬人和收款人的賬戶名
String accountFromKey = args.get(0);
String accountToKey = args.get(1);
//擷取轉賬人賬戶餘額，字元串形式
String accountFromValueStr = stub.getStringState(accountFromKey);
if (accountFromValueStr == null) {
return newErrorResponse(String.format("Entity %s not found", accountFromKey));
}
//擷取轉賬人餘額，整數形式
int accountFromValue = Integer.parseInt(accountFromValueStr);
//擷取收款人餘額，字元串形式
String accountToValueStr = stub.getStringState(accountToKey);
if (accountToValueStr == null) {
return newErrorResponse(String.format("Entity %s not found", accountToKey));
}
//擷取收款人餘額，
int accountToValue = Integer.parseInt(accountToValueStr);
//擷取轉賬金額
int amount = Integer.parseInt(args.get(2));
if (amount > accountFromValue) {
return newErrorResponse(String.format("not enough money in account %s", accountFromKey));
}
accountFromValue -= amount;
accountToValue += amount;
_logger.info(String.format("new value of A: %s", accountFromValue));
_logger.info(String.format("new value of B: %s", accountToValue));
//把雙方轉帳後剩多少，更新上去
stub.putStringState(accountFromKey, Integer.toString(accountFromValue));
stub.putStringState(accountToKey, Integer.toString(accountToValue));
_logger.info("Transfer complete");
return newSuccessResponse("invoke finished successfully", ByteString.copyFrom(accountFromKey + ": " + accountFromValue + " " + accountToKey + ": " + accountToValue, UTF_8).toByteArray());
}
delete
// Deletes an entity from state
//從賬本中删除實體
private Response delete(ChaincodeStub stub, List<String> args) {
if (args.size() != 1) {
return newErrorResponse("Incorrect number of arguments. Expecting 1");
}
String key = args.get(0);
// Delete the key from the state in ledger
stub.delState(key);
return newSuccessResponse();
}
query。query方法提供對賬戶餘額的查詢
// query callback representing the query of a chaincode
private Response query(ChaincodeStub stub, List<String> args) {
if (args.size() != 1) {
return newErrorResponse("Incorrect number of arguments. Expecting name of the person to query");
}
String key = args.get(0);
//byte[] stateBytes
String val = stub.getStringState(key);
if (val == null) {
return newErrorResponse(String.format("Error: state for %s is null", key));
}
_logger.info(String.format("Query Response:\nName: %s, Amount: %s\n", key, val));
return newSuccessResponse(val, ByteString.copyFrom(val, UTF_8).toByteArray());
}
public static void main(String[] args) {
System.out.println("OpenSSL avaliable: " + OpenSsl.isAvailable());
new SimpleChaincode().start(args);
}
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