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 getTransferEvents(TransactionReceipt transactionReceipt) {

...

return responses;

}

public Observable transferEventObservable(DefaultBlockParameter startBlock, DefaultBlockParameter endBlock) {

...

}

...

public Uint256 balanceOf(Address _owner) throws IOException {

Function function = new Function("balanceOf",

Arrays.asList(_owner),

Arrays.>asList(new TypeReference() {}));

return executeCallSingleValueReturn(function);

}

...

public TransactionReceipt transfer(Address _to, Uint256 _amount) throws IOException, TransactionException {

Function function = new Function("transfer", Arrays.asList(_to, _amount), Collections.>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。

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.

* Do not modify!

* Please use the web3j command line tools, or {@link org.web3j.codegen.SolidityFunctionWrapperGenerator} to update.

*

*

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 getTransferEvents(TransactionReceipt transactionReceipt) {

final Event event = new Event("Transfer",

Arrays.>asList(new TypeReference

() {}, new TypeReference

() {}),

Arrays.>asList(new TypeReference() {}));

List valueList = extractEventParameters(event, transactionReceipt);

ArrayList responses = new ArrayList(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 transferEventObservable(DefaultBlockParameter startBlock, DefaultBlockParameter endBlock) {

final Event event = new Event("Transfer",

Arrays.>asList(new TypeReference

() {}, new TypeReference

() {}),

Arrays.>asList(new TypeReference() {}));

EthFilter filter = new EthFilter(startBlock, endBlock, getContractAddress());

filter.addSingleTopic(EventEncoder.encode(event));

return web3j.ethLogObservable(filter).map(new Func1() {

@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 getApprovalEvents(TransactionReceipt transactionReceipt) {

final Event event = new Event("Approval",

Arrays.>asList(new TypeReference

() {}, new TypeReference

() {}),

Arrays.>asList(new TypeReference() {}));

List valueList = extractEventParameters(event, transactionReceipt);

ArrayList responses = new ArrayList(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 approvalEventObservable(DefaultBlockParameter startBlock, DefaultBlockParameter endBlock) {

final Event event = new Event("Approval",

Arrays.>asList(new TypeReference

() {}, new TypeReference

() {}),

Arrays.>asList(new TypeReference() {}));

EthFilter filter = new EthFilter(startBlock, endBlock, getContractAddress());

filter.addSingleTopic(EventEncoder.encode(event));

return web3j.ethLogObservable(filter).map(new Func1() {

@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 name() throws IOException {

Function function = new Function("name",

Arrays.asList(),

Arrays.>asList(new TypeReference() {}));

return executeCallSingleValueReturn(function);

}

public TransactionReceipt approve(Address _spender, Uint256 _amount) throws IOException, TransactionException {

Function function = new Function("approve", Arrays.asList(_spender, _amount), Collections.>emptyList());

return executeTransaction(function);

}

public Future totalSupply() throws IOException {

Function function = new Function("totalSupply",

Arrays.asList(),

Arrays.>asList(new TypeReference() {}));

return executeCallSingleValueReturn(function);

}

public TransactionReceipt transferFrom(Address _from, Address _to, Uint256 _amount) throws IOException, TransactionException {

Function function = new Function("transferFrom", Arrays.asList(_from, _to, _amount), Collections.>emptyList());

return executeTransaction(function);

}

public Uint8 decimals() throws IOException {

Function function = new Function("decimals",

Arrays.asList(),

Arrays.>asList(new TypeReference() {}));

return executeCallSingleValueReturn(function);

}

public Uint256 balanceOf(Address _owner) throws IOException {

Function function = new Function("balanceOf",

Arrays.asList(_owner),

Arrays.>asList(new TypeReference() {}));

return executeCallSingleValueReturn(function);

}

public Future

owner() throws IOException {

Function function = new Function("owner",

Arrays.asList(),

Arrays.>asList(new TypeReference

() {}));

return executeCallSingleValueReturn(function);

}

public Future symbol() throws IOException {

Function function = new Function("symbol",

Arrays.asList(),

Arrays.>asList(new TypeReference() {}));

return executeCallSingleValueReturn(function);

}

public TransactionReceipt transfer(Address _to, Uint256 _amount) throws IOException, TransactionException {

Function function = new Function("transfer", Arrays.asList(_to, _amount), Collections.>emptyList());

return executeTransaction(function);

}

public Future allowance(Address _owner, Address _spender) throws IOException {

Function function = new Function("allowance",

Arrays.asList(_owner, _spender),

Arrays.>asList(new TypeReference() {}));

return executeCallSingleValueReturn(function);

}

public static RemoteCall deploy(Web3j web3j, Credentials credentials, BigInteger gasPrice, BigInteger gasLimit, BigInteger initialWeiValue, Uint256 totalSupply, Utf8String tokenName, Uint8 decimalUnits, Utf8String tokenSymbol) {

String encodedConstructor = FunctionEncoder.encodeConstructor(Arrays.asList(totalSupply, tokenName, decimalUnits, tokenSymbol));

return deployRemoteCall(Erc20TokenWrapper.class, web3j, credentials, gasPrice, gasLimit, BINARY, encodedConstructor, initialWeiValue);

}

public static RemoteCall deploy(Web3j web3j, TransactionManager transactionManager, BigInteger gasPrice, BigInteger gasLimit, BigInteger initialWeiValue, Uint256 totalSupply, Utf8String tokenName, Uint8 decimalUnits, Utf8String tokenSymbol) {

String encodedConstructor = FunctionEncoder.encodeConstructor(Arrays.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;

}

}