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如何使用java监听Erc20Token交易

你可以在web3j库的帮助下使用java轻松监听以太坊交易，但此库无法监听Erc20 Token交易。

要监听Erc20Token交易，你必须使用在合约（token）创建时的 token 封装类。我假设你已经使用最少的功能部署了合约，因此你的封装类看起来像这样：

package com.bolenum.util;

import java.io.IOException;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util...;

import org.web3j.abi.EventEncoder;
import org.web3j.abi...
import org.web3j.crypto.Credentials;
import org.web3j.protocol.Web3j;
import org.web3j.protocol...;
import org.web3j.tx.Contract;
import org.web3j.tx.TransactionManager;

import rx.Observable;
import rx.functions.Func1;

...

public final class Erc20TokenWrapper extends Contract {

    private static final String BINARY = "contract binary key";

    private Erc20TokenWrapper(String contractAddress, Web3j web3j, Credentials credentials, BigInteger gasPrice, BigInteger gasLimit) {
        super(BINARY, contractAddress, web3j, credentials, gasPrice, gasLimit);
    }

    private Erc20TokenWrapper(String contractAddress, Web3j web3j, TransactionManager transactionManager, BigInteger gasPrice, BigInteger gasLimit) {
        super(BINARY, contractAddress, web3j, transactionManager, gasPrice, gasLimit);
    }

    public List<TransferEventResponse> getTransferEvents(TransactionReceipt transactionReceipt) {
        ...
        return responses;
    }

    public Observable<TransferEventResponse> transferEventObservable(DefaultBlockParameter startBlock, DefaultBlockParameter endBlock) {
		...
	}

	...
	
    public Uint256 balanceOf(Address _owner) throws IOException {
        Function function = new Function("balanceOf", 
                Arrays.<Type>asList(_owner), 
                Arrays.<TypeReference<?>>asList(new TypeReference<Uint256>() {}));
        return executeCallSingleValueReturn(function);
    }

	...
	
    public TransactionReceipt transfer(Address _to, Uint256 _amount) throws IOException, TransactionException {
        Function function = new Function("transfer", Arrays.<Type>asList(_to, _amount), Collections.<TypeReference<?>>emptyList());
        return executeTransaction(function);
    }

    ...
   
    public static Erc20TokenWrapper load(String contractAddress, Web3j web3j, TransactionManager transactionManager, BigInteger gasPrice, BigInteger gasLimit) {
        return new Erc20TokenWrapper(contractAddress, web3j, transactionManager, gasPrice, gasLimit);
    }

    public static class TransferEventResponse {
        public Address _from;
        public Address _to;
        public Uint256 _value;
        public String _transactionHash;
    }
	
	...
}

现在你必须使用这个类函数来加载合约然后监听交易。使用下面的代码加载和监听交易：

Web3j web3j = Web3j.build(new HttpService("url of your ethereum blockchain"))    
ClientTransactionManager transactionManager = new ClientTransactionManager(web3j,
                    "your deployed contract addess");
            Erc20TokenWrapper token = Erc20TokenWrapper.load("your deployed contract addess", web3j, transactionManager,
                    Contract.GAS_PRICE, Contract.GAS_LIMIT);
            token.transferEventObservable(DefaultBlockParameterName.EARLIEST, DefaultBlockParameterName.LATEST)
                    .subscribe(tx -> {
                                   String toAddress = tx._to.getValue();
                                   String fromAddress = tx._from.getValue();
                                   String txHash = tx._transactionHash.getValue();
                               }

如果你已经部署了合约，它由第三人部署，那么你可以直接使用我的包装类，只需更改你可以从 https://etherscan.io/tokens 很容易获得的二进制密钥。

结论：因此你可以将此代码用于任何token的监听交易。此代码为你提供 address ， fromAddress 和 transactionHash 。所以这些东西你可以根据你的要求使用，你可以将它们保存在你的数据库中，或者你只保存地址是你的钱包地址的交易。

谢谢，我希望这会有所帮助。

如果希望快速进行web3j、java、以太坊开发，那请看我们精心打造的教程：java以太坊开发教程，主要是针对java和android程序员进行区块链以太坊开发的web3j详解。

其他以太坊教程如下：

以太坊入门教程，主要介绍智能合约与dapp应用开发，适合入门。
以太坊开发进阶教程，主要是介绍使用node.js、mongodb、区块链、ipfs实现去中心化电商DApp实战，适合进阶。
python以太坊，主要是针对python工程师使用web3.py进行区块链以太坊开发的详解。
php以太坊，主要是介绍使用php进行智能合约开发交互，进行账号创建、交易、转账、代币开发以及过滤器和事件等内容。
C#以太坊，主要讲解如何使用C#开发基于.Net的以太坊应用，包括账户管理、状态与交易、智能合约开发与交互、过滤器和事件等。

汇智网原创翻译，转载请标明出处。这里是原文

完整代码如下：

package com.bolenum.util;

import java.io.IOException;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.Future;

import org.web3j.abi.EventEncoder;
import org.web3j.abi.EventValues;
import org.web3j.abi.FunctionEncoder;
import org.web3j.abi.TypeReference;
import org.web3j.abi.datatypes.Address;
import org.web3j.abi.datatypes.Event;
import org.web3j.abi.datatypes.Function;
import org.web3j.abi.datatypes.Type;
import org.web3j.abi.datatypes.Utf8String;
import org.web3j.abi.datatypes.generated.Uint256;
import org.web3j.abi.datatypes.generated.Uint8;
import org.web3j.crypto.Credentials;
import org.web3j.protocol.Web3j;
import org.web3j.protocol.core.DefaultBlockParameter;
import org.web3j.protocol.core.RemoteCall;
import org.web3j.protocol.core.methods.request.EthFilter;
import org.web3j.protocol.core.methods.response.Log;
import org.web3j.protocol.core.methods.response.TransactionReceipt;
import org.web3j.protocol.exceptions.TransactionException;
import org.web3j.tx.Contract;
import org.web3j.tx.TransactionManager;

import rx.Observable;
import rx.functions.Func1;

/**
 * Auto generated code.<br>
 * <strong>Do not modify!</strong><br>
 * Please use the <a href="https://docs.web3j.io/command_line.html">web3j command line tools</a>, or {@link org.web3j.codegen.SolidityFunctionWrapperGenerator} to update.
 *
 * <p>Generated with web3j version 2.3.1.
 */
public final class Erc20TokenWrapper extends Contract {

    private static final String BINARY = "contract binary key";

    private Erc20TokenWrapper(String contractAddress, Web3j web3j, Credentials credentials, BigInteger gasPrice, BigInteger gasLimit) {
        super(BINARY, contractAddress, web3j, credentials, gasPrice, gasLimit);
    }

    private Erc20TokenWrapper(String contractAddress, Web3j web3j, TransactionManager transactionManager, BigInteger gasPrice, BigInteger gasLimit) {
        super(BINARY, contractAddress, web3j, transactionManager, gasPrice, gasLimit);
    }

    public List<TransferEventResponse> getTransferEvents(TransactionReceipt transactionReceipt) {
        final Event event = new Event("Transfer", 
                Arrays.<TypeReference<?>>asList(new TypeReference<Address>() {}, new TypeReference<Address>() {}),
                Arrays.<TypeReference<?>>asList(new TypeReference<Uint256>() {}));
        List<EventValues> valueList = extractEventParameters(event, transactionReceipt);
        ArrayList<TransferEventResponse> responses = new ArrayList<TransferEventResponse>(valueList.size());
        for (EventValues eventValues : valueList) {
            TransferEventResponse typedResponse = new TransferEventResponse();
            typedResponse._from = (Address) eventValues.getIndexedValues().get(0);
            typedResponse._to = (Address) eventValues.getIndexedValues().get(1);
            typedResponse._value = (Uint256) eventValues.getNonIndexedValues().get(0);
            responses.add(typedResponse);
        }
        return responses;
    }

    public Observable<TransferEventResponse> transferEventObservable(DefaultBlockParameter startBlock, DefaultBlockParameter endBlock) {
        final Event event = new Event("Transfer", 
                Arrays.<TypeReference<?>>asList(new TypeReference<Address>() {}, new TypeReference<Address>() {}),
                Arrays.<TypeReference<?>>asList(new TypeReference<Uint256>() {}));
        EthFilter filter = new EthFilter(startBlock, endBlock, getContractAddress());
        filter.addSingleTopic(EventEncoder.encode(event));
        return web3j.ethLogObservable(filter).map(new Func1<Log, TransferEventResponse>() {
            @Override
            public TransferEventResponse call(Log log) {
                EventValues eventValues = extractEventParameters(event, log);
                TransferEventResponse typedResponse = new TransferEventResponse();
                typedResponse._from = (Address) eventValues.getIndexedValues().get(0);
                typedResponse._to = (Address) eventValues.getIndexedValues().get(1);
                typedResponse._value = (Uint256) eventValues.getNonIndexedValues().get(0);
                typedResponse._transactionHash = log.getTransactionHash();
                return typedResponse;
            }
        });
    }

    public List<ApprovalEventResponse> getApprovalEvents(TransactionReceipt transactionReceipt) {
        final Event event = new Event("Approval", 
                Arrays.<TypeReference<?>>asList(new TypeReference<Address>() {}, new TypeReference<Address>() {}),
                Arrays.<TypeReference<?>>asList(new TypeReference<Uint256>() {}));
        List<EventValues> valueList = extractEventParameters(event, transactionReceipt);
        ArrayList<ApprovalEventResponse> responses = new ArrayList<ApprovalEventResponse>(valueList.size());
        for (EventValues eventValues : valueList) {
            ApprovalEventResponse typedResponse = new ApprovalEventResponse();
            typedResponse._owner = (Address) eventValues.getIndexedValues().get(0);
            typedResponse._spender = (Address) eventValues.getIndexedValues().get(1);
            typedResponse._value = (Uint256) eventValues.getNonIndexedValues().get(0);
            responses.add(typedResponse);
        }
        return responses;
    }

    public Observable<ApprovalEventResponse> approvalEventObservable(DefaultBlockParameter startBlock, DefaultBlockParameter endBlock) {
        final Event event = new Event("Approval", 
                Arrays.<TypeReference<?>>asList(new TypeReference<Address>() {}, new TypeReference<Address>() {}),
                Arrays.<TypeReference<?>>asList(new TypeReference<Uint256>() {}));
        EthFilter filter = new EthFilter(startBlock, endBlock, getContractAddress());
        filter.addSingleTopic(EventEncoder.encode(event));
        return web3j.ethLogObservable(filter).map(new Func1<Log, ApprovalEventResponse>() {
            @Override
            public ApprovalEventResponse call(Log log) {
                EventValues eventValues = extractEventParameters(event, log);
                ApprovalEventResponse typedResponse = new ApprovalEventResponse();
                typedResponse._owner = (Address) eventValues.getIndexedValues().get(0);
                typedResponse._spender = (Address) eventValues.getIndexedValues().get(1);
                typedResponse._value = (Uint256) eventValues.getNonIndexedValues().get(0);
                typedResponse._transactionHash = log.getTransactionHash();
                return typedResponse;
            }
        });
    }

    public Future<Utf8String> name() throws IOException {
        Function function = new Function("name", 
                Arrays.<Type>asList(), 
                Arrays.<TypeReference<?>>asList(new TypeReference<Utf8String>() {}));
        return executeCallSingleValueReturn(function);
    }

    public TransactionReceipt approve(Address _spender, Uint256 _amount) throws IOException, TransactionException {
        Function function = new Function("approve", Arrays.<Type>asList(_spender, _amount), Collections.<TypeReference<?>>emptyList());
        return executeTransaction(function);
    }

    public Future<Uint256> totalSupply() throws IOException {
        Function function = new Function("totalSupply", 
                Arrays.<Type>asList(), 
                Arrays.<TypeReference<?>>asList(new TypeReference<Uint256>() {}));
        return executeCallSingleValueReturn(function);
    }

    public TransactionReceipt transferFrom(Address _from, Address _to, Uint256 _amount) throws IOException, TransactionException {
        Function function = new Function("transferFrom", Arrays.<Type>asList(_from, _to, _amount), Collections.<TypeReference<?>>emptyList());
        return  executeTransaction(function);
    }

    public Uint8 decimals() throws IOException {
        Function function = new Function("decimals", 
                Arrays.<Type>asList(), 
                Arrays.<TypeReference<?>>asList(new TypeReference<Uint8>() {}));
        return executeCallSingleValueReturn(function);
    }

    public Uint256 balanceOf(Address _owner) throws IOException {
        Function function = new Function("balanceOf", 
                Arrays.<Type>asList(_owner), 
                Arrays.<TypeReference<?>>asList(new TypeReference<Uint256>() {}));
        return executeCallSingleValueReturn(function);
    }

    public Future<Address> owner() throws IOException {
        Function function = new Function("owner", 
                Arrays.<Type>asList(), 
                Arrays.<TypeReference<?>>asList(new TypeReference<Address>() {}));
        return executeCallSingleValueReturn(function);
    }

    public Future<Utf8String> symbol() throws IOException {
        Function function = new Function("symbol", 
                Arrays.<Type>asList(), 
                Arrays.<TypeReference<?>>asList(new TypeReference<Utf8String>() {}));
        return executeCallSingleValueReturn(function);
    }

    public TransactionReceipt transfer(Address _to, Uint256 _amount) throws IOException, TransactionException {
        Function function = new Function("transfer", Arrays.<Type>asList(_to, _amount), Collections.<TypeReference<?>>emptyList());
        return executeTransaction(function);
    }

    public Future<Uint256> allowance(Address _owner, Address _spender) throws IOException {
        Function function = new Function("allowance", 
                Arrays.<Type>asList(_owner, _spender), 
                Arrays.<TypeReference<?>>asList(new TypeReference<Uint256>() {}));
        return executeCallSingleValueReturn(function);
    }

    public static RemoteCall<Erc20TokenWrapper> deploy(Web3j web3j, Credentials credentials, BigInteger gasPrice, BigInteger gasLimit, BigInteger initialWeiValue, Uint256 totalSupply, Utf8String tokenName, Uint8 decimalUnits, Utf8String tokenSymbol) {
        String encodedConstructor = FunctionEncoder.encodeConstructor(Arrays.<Type>asList(totalSupply, tokenName, decimalUnits, tokenSymbol));
        return deployRemoteCall(Erc20TokenWrapper.class, web3j, credentials, gasPrice, gasLimit, BINARY, encodedConstructor, initialWeiValue);
    }

    public static RemoteCall<Erc20TokenWrapper> deploy(Web3j web3j, TransactionManager transactionManager, BigInteger gasPrice, BigInteger gasLimit, BigInteger initialWeiValue, Uint256 totalSupply, Utf8String tokenName, Uint8 decimalUnits, Utf8String tokenSymbol) {
        String encodedConstructor = FunctionEncoder.encodeConstructor(Arrays.<Type>asList(totalSupply, tokenName, decimalUnits, tokenSymbol));
        return deployRemoteCall(Erc20TokenWrapper.class, web3j, transactionManager, gasPrice, gasLimit, BINARY, encodedConstructor, initialWeiValue);
    }

    public static Erc20TokenWrapper load(String contractAddress, Web3j web3j, Credentials credentials, BigInteger gasPrice, BigInteger gasLimit) {
        return new Erc20TokenWrapper(contractAddress, web3j, credentials, gasPrice, gasLimit);
    }

    public static Erc20TokenWrapper load(String contractAddress, Web3j web3j, TransactionManager transactionManager, BigInteger gasPrice, BigInteger gasLimit) {
        return new Erc20TokenWrapper(contractAddress, web3j, transactionManager, gasPrice, gasLimit);
    }

    public static class TransferEventResponse {
        public Address _from;

        public Address _to;

        public Uint256 _value;

        public String _transactionHash;
    }

    public static class ApprovalEventResponse {
        public Address _owner;

        public Address _spender;

        public Uint256 _value;

        public String _transactionHash;
    }
}

原文 http://blog.hubwiz.com/2018/08/27/ethereum-java-Listen-Erc20Token/

正文到此结束