Ontology Java SDK User Guide

Version 0.7.0

Smart Contract

What is codeAddress?

codeAddress is the unique identifier of smart contract.

how to get codeAddress?

InputStream is = new FileInputStream("IdContract.avm");
byte[] bys = new byte[is.available()];
is.read(bys);
is.close();
code = Helper.toHexString(bys);
System.out.println("Code:" + Helper.toHexString(bys));
System.out.println("CodeAddress:" + Helper.getCodeAddress(code, VmType.NEOVM.value()));

Note: When you get the codeAddress, you need to set which virtual machine the contract needs to run on. The java-sdk currently supported virtual machines are NEO and WASM.。

What would sdk do in detail when calling the invokeTransaction function of smart contract?

//step1：construct transaction
//Firstly, convert the parameters of smart contract into the vm-recognizable opcode 
Transaction tx = ontSdk.getSmartcodeTx().makeInvokeCodeTransaction(params, vmtype, fees);

//step2：sign the transaction
ontSdk.signTx(tx, info1.address, password);

//step3：send the transaction
ontSdk.getConnectMgr().sendRawTransaction(tx.toHexString());

Why do we need to pass the account and its password when invoking?

User’s signature, which is generated by the private key, is neccesary in the process of invoking a smart contract. The private key is encrypted and stored in the wallet, and need the password to decrypt.

What is the pre-execution of smart contract when querying the assert and how to use it?

Operations of smart contract, such as get, do not need to go through any consensus node. They read data directly from the storage of smart contract, execute at current node, and return the result. We can call the pre-execution interface while sending transactions.

String result = (String) sdk.getConnectMgr().sendRawTransactionPreExec(txHex);

Deployment and invocation of smart contract

Note: At present, java-sdk supports neo and wasm smart contract deployment and invocation. Deployment operations of NEO and WASM contract are the same,but the invocation is slightly different. See below for details.

A deployment example of smart contract

InputStream is = new FileInputStream("/Users/sss/dev/ontologytest/IdContract/IdContract.avm");
byte[] bys = new byte[is.available()];
is.read(bys);
is.close();
code = Helper.toHexString(bys);
ontSdk.setCodeAddress(Helper.getCodeAddress(codeHexStr,vmtype));

//Deploy the contract
String txhash = ontSdk.getSmartcodeTx().makeDeployCodeTransaction(code, true, "name", "1.0", "1", "1", "1", VmType.NEOVM.value());
System.out.println("txhash:" + txhash);
//Waiting for block generation
Thread.sleep(6000);
DeployCodeTransaction t = (DeployCodeTransaction) ontSdk.getConnectMgr().getTransaction(txhash);

Invocation of smart contract

Invocation of NEO smart contarct

Basic process
1. Read the abi file of smart contract;
2. construct the function that calls the smart contract;
3. construct trasanction;
4. sign transaction;
5. send transactions.
example:

//Load the abi file of smart contract
InputStream is = new FileInputStream("C:\\ZX\\NeoContract1.abi.json");
byte[] bys = new byte[is.available()];
is.read(bys);
is.close();
String abi = new String(bys);
            
//Interpret the abi file
AbiInfo abiinfo = JSON.parseObject(abi, AbiInfo.class);
System.out.println("codeHash:"+abiinfo.getHash());
System.out.println("Entrypoint:"+abiinfo.getEntrypoint());
System.out.println("Functions:"+abiinfo.getFunctions());
System.out.println("Events"+abiinfo.getEvents());

//Set the codeAddress of smart contract
ontSdk.setCodeAddress(abiinfo.getHash());

//Obtain the accound informations
Identity did = ontSdk.getWalletMgr().getIdentitys().get(0);
AccountInfo info = ontSdk.getWalletMgr().getAccountInfo(did.ontid,"passwordtest");

//Construct the smart contract function
AbiFunction func = abiinfo.getFunction("AddAttribute");
System.out.println(func.getParameters());
func.setParamsValue(did.ontid.getBytes(),"key".getBytes(),"bytes".getBytes(),"values02".getBytes(),Helper.hexToBytes(info.pubkey));

//Call a smart contract, sendInvokeSmartCodeWithSign method encapsulates a structured transaction, signing a transaction, sending a transaction step
String hash = ontSdk.getSmartcodeTx().sendInvokeSmartCodeWithSign(did.ontid, "passwordtest", func, (byte) VmType.NEOVM.value());

What would be the AbiInfo structure?

public class AbiInfo {
    public String hash;
    public String entrypoint;
    public List<AbiFunction> functions;
    public List<AbiEvent> events;
}
public class AbiFunction {
    public String name;
    public String returntype;
    public List<Parameter> parameters;
}
public class Parameter {
    public String name;
    public String type;
    public String value;
}

Invocation of WASM smart contract

basic process：
1. Constructing the parameters required by the method in the calling contract；
2. Structure transaction；
3. Transaction signature (no signature required for pre-execution)；
4. send Transaction。
example：

//set codeAddress
ontSdk.getSmartcodeTx().setCodeAddress(codeAddress);
String funcName = "add";
//The parameters needed to construct a contract function
String params = ontSdk.getSmartcodeTx().buildWasmContractJsonParam(new Object[]{20,30});
//Specify a virtual machine type to construct a transaction
Transaction tx = ontSdk.getSmartcodeTx().makeInvokeCodeTransaction(ontSdk.getSmartcodeTx().getCodeAddress(),funcName,params.getBytes(),VmType.WASMVM.value(),new Fee[0]);
//send transaction
ontSdk.getConnectMgr().sendRawTransaction(tx.toHexString());

Read the following chapter if you need to monitor the push notification

Process smart contract push notifications

Create a websocket thread and analyse the push notification.

Set websocket link

//lock global variable, synchronization lock
public static Object lock = new Object();

//Get ont instance
String ip = "http://127.0.0.1";
String wsUrl = ip + ":" + "20335";
OntSdk wm = OntSdk.getInstance();
wm.setWesocket(wsUrl, lock);
wm.setDefaultConnect(wm.getWebSocket());
wm.openWalletFile("OntAssetDemo.json");

Start websocket thread

//false means not printing callback function information
ontSdk.getWebSocket().startWebsocketThread(false);

Start result processing thread

Thread thread = new Thread(
                    new Runnable() {
                        @Override
                        public void run() {
                            waitResult(lock);
                        }
                    });
            thread.start();
            //Take out the data in the MsgQueue print
            public static void waitResult(Object lock) {
                    try {
                        synchronized (lock) {
                            while (true) {
                                lock.wait();
                                for (String e : MsgQueue.getResultSet()) {
                                    System.out.println("RECV: " + e);
                                    Result rt = JSON.parseObject(e, Result.class);
                                    //TODO
                                    MsgQueue.removeResult(e);
                                    if (rt.Action.equals("getblockbyheight")) {
                                        Block bb = Serializable.from(Helper.hexToBytes((String) rt.Result), Block.class);
                                        //System.out.println(bb.json());
                                    }
                                }
                            }
                        }
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }

Send a heartbeat every 6 seconds to maintain the socket link

for (;;){
                    Map map = new HashMap();
                    if(i >0) {
                        map.put("SubscribeEvent", true);
                        map.put("SubscribeRawBlock", false);
                    }else{
                        map.put("SubscribeJsonBlock", false);
                        map.put("SubscribeRawBlock", true);
                    }
                    //System.out.println(map);
                    ontSdk.getWebSocket().setReqId(i);
                    ontSdk.getWebSocket().sendSubscribe(map);     
                Thread.sleep(6000);
            }

Push result case details

Take the put event of the deposit certificate as an example.

//The certificate abi.json document is as follows.

{
    "hash":"0x27f5ae9dd51499e7ac4fe6a5cc44526aff909669",
    "entrypoint":"Main",
    "functions":
    [
        
    ],
    "events":
    [
        {
            "name":"putRecord",
            "parameters":
            [
                {
                    "name":"arg1",
                    "type":"String"
                },
                {
                    "name":"arg2",
                    "type":"ByteArray"
                },
                {
                    "name":"arg3",
                    "type":"ByteArray"
                }
            ],
            "returntype":"Void"
        }
    ]
}

When the put function is called to save the data, the putRecord event is fired. The result of the websocket push is the hexadecimal string of {“putRecord”, “arg1”, “arg2”, “arg3”}

example:

RECV: {"Action":"Log","Desc":"SUCCESS","Error":0,"Result":{"Message":"Put","TxHash":"8cb32f3a1817d88d8562fdc0097a0f9aa75a926625c6644dfc5417273ca7ed71","ContractAddress":"80f6bff7645a84298a1a52aa3745f84dba6615cf"},"Version":"1.0.0"}
RECV: {"Action":"Notify","Desc":"SUCCESS","Error":0,"Result":[{"States":["7075745265636f7264","507574","6b6579","7b2244617461223a7b22416c6772697468656d223a22534d32222c2248617368223a22222c2254657874223a2276616c75652d7465737431222c225369676e6174757265223a22227d2c2243416b6579223a22222c225365714e6f223a22222c2254696d657374616d70223a307d"],"TxHash":"8cb32f3a1817d88d8562fdc0097a0f9aa75a926625c6644dfc5417273ca7ed71","ContractAddress":"80f6bff7645a84298a1a52aa3745f84dba6615cf"}],"Version":"1.0.0"}