① 查詢鏈上數(shù)據(jù)用的rpc（本示例是binance的，測試網(wǎng)可以使用：https://data-seed-prebsc-2-s2.binance.org:8545）
② 自己還要有一個(gè)測試鏈上部署好的合約，合約中要有一個(gè)方法emit了事件。
③ java依賴
<dependency>
<groupId>org.web3j</groupId>
<artifactId>core</artifactId>
<version>4.9.7</version>
</dependency>
<dependency>
<groupId>org.web3j</groupId>
<artifactId>codegen</artifactId>
<version>4.9.7</version>
</dependency>一、通過自己合約的abi和bin生成一個(gè)java文件，abi和bin可以在remix的compiler模塊中獲取，代碼如下（這一步懶得做的可以跳過，在第二步傳合約地址的時(shí)候，直接傳一個(gè)字符串也行。這里就是順手存一下這個(gè)方法，其實(shí)實(shí)際使用也是直接傳的字符串，具體可以看頁面最下方的”三、“）
/**
* 通過合約abi和bin獲得java文件
*/
public void getJavaFileBySolidity(){
// 生成的java類名，同ABI文件同名，自動(dòng)首字母大寫
String packageName = "";
String outDirPath = "/Users/maomo/Desktop/";
String binDirPath = "/Users/maomo/Desktop/xxxbin.txt";
String abiDirPath = "/Users/maomo/Desktop/xxxabi.txt";
String[] arr = Arrays.asList(
"-b", binDirPath,
"-a", abiDirPath,
"-p", packageName,
"-o", outDirPath
).toArray(new String[0]);
SolidityFunctionWrapperGenerator.main(arr);
}二、通過web3j查詢事件，通過event和ethFilter增加過濾條件
public void testSub() {
Web3j web3j = Web3j.build(new HttpService("https://data-seed-prebsc-2-s2.binance.org:8545"));
//第一步生成的合約實(shí)體
Contract contract;
Disposable subscribe = null;
try {
Web3ClientVersion web3ClientVersion = web3j.web3ClientVersion().send();
String clientVersion = web3ClientVersion.getWeb3ClientVersion();
log.info("wen3j subscribe --clientVersion-- :{} ", clientVersion);
//設(shè)置誰調(diào)用合約
TransactionManager transactionManager = new ClientTransactionManager(web3j, "這里可以輸入自己的錢包地址");
//加載智能合約（此處可以跳過，下面穿合約地址的地方 直接傳字符串）
contract = Contract.load("你要監(jiān)聽的合約地址", web3j, transactionManager, ManagedTransaction.GAS_PRICE, org.web3j.tx.Contract.GAS_LIMIT);
//設(shè)置過濾條件 這個(gè)示例是監(jiān)聽最新的1000個(gè)塊
BigInteger blockNumber = web3j.ethBlockNumber().send().getBlockNumber()
.subtract(new BigInteger("1000"));
EthFilter ethFilter = new EthFilter(DefaultBlockParameter.valueOf(blockNumber),DefaultBlockParameterName.LATEST, contract.getContractAddress());
//監(jiān)聽哪個(gè)事件，合約中的event寫了幾個(gè)參數(shù)，這里就寫幾個(gè)，類型對應(yīng)好
Event event = new Event("startEvent",
Arrays.<TypeReference<?>>asList(
new TypeReference<Address>(true) {},
new TypeReference<Address>(true) {},
new TypeReference<Uint256>(true) {},
new TypeReference<Uint256>(false) {},
new TypeReference<Uint256>(false) {},
new TypeReference<Uint256>(false) {}));
ethFilter.addSingleTopic(EventEncoder.encode(event));
subscribe = web3j.ethLogFlowable(ethFilter).subscribe(tx -> {
int newBlock = tx.getBlockNumber().intValue();
log.info("wen3j subscribe --newBlock-- :{} ", newBlock);
log.info("wen3j subscribe --tx-- :{} ", tx);
EventValues eventValues = staticExtractEventParameters(event, tx);
//定義接收參數(shù)(本示例使用的事件返回了6個(gè)，具體按自己合約來)
String address1 = "";String address2 = "";int uint1 = 0;
int uint2 = 0;int uint3 = 0;int uint4 = 0;
List<Type> indexedValues = eventValues.getIndexedValues();
if (ObjectUtils.isNotEmpty(indexedValues) && indexedValues.size() == 3) {
Type type1 = indexedValues.get(0);
address1 = type1.getValue().toString();
Type type2 = indexedValues.get(1);
address2 = type2.getValue().toString();
Type type3 = indexedValues.get(2);
uint1 = Integer.parseInt(type3.getValue().toString());
}
List<Type> nonIndexedValues = eventValues.getNonIndexedValues();
if (ObjectUtils.isNotEmpty(nonIndexedValues) && nonIndexedValues.size() == 3) {
Type type1 = nonIndexedValues.get(0);
uint2 = Integer.parseInt(type1.getValue().toString());
Type type2 = nonIndexedValues.get(1);
uint3 = Integer.parseInt(type2.getValue().toString());
Type type3 = nonIndexedValues.get(2);
uint4 = Integer.parseInt(type3.getValue().toString());
}
log.info("address1:{};address2:{};uint1:{};uint2:{};uint3:{};uint4:{}",address1, address2, uint1, uint2, uint3, uint4);
});
}catch (Exception e) {
e.printStackTrace();
}finally {
//關(guān)閉監(jiān)聽
if(ObjectUtils.isNotEmpty(subscribe) && !subscribe.isDisposed()){
subscribe.dispose();
}
}
} /**
* 解析log返回的data
* @param event 合約中定義的事件
* @param log 監(jiān)聽到的log
* @return 解析后的數(shù)據(jù)
*/
public EventValues staticExtractEventParameters(Event event, Log log) {
final List<String> topics = log.getTopics();
String encodedEventSignature = EventEncoder.encode(event);
if (topics == null || topics.size() == 0 || !topics.get(0).equals(encodedEventSignature)) {
return null;
}
List<Type> indexedValues = new ArrayList<>();
List<Type> nonIndexedValues = FunctionReturnDecoder.decode(
log.getData(), event.getNonIndexedParameters());
List<TypeReference<Type>> indexedParameters = event.getIndexedParameters();
for (int i = 0; i < indexedParameters.size(); i++) {
Type value = FunctionReturnDecoder.decodeIndexedValue(
topics.get(i + 1), indexedParameters.get(i));
indexedValues.add(value);
}
return new EventValues(indexedValues, nonIndexedValues);
}三、為了方便以后復(fù)制粘貼(不是)，最下面再傳一個(gè)不生成合約的版本
public void testSub() {
Web3j web3j = Web3j.build(new HttpService("https://data-seed-prebsc-2-s2.binance.org:8545"));
//第一步生成的合約實(shí)體
Contract contract;
Disposable subscribe = null;
try {
Web3ClientVersion web3ClientVersion = web3j.web3ClientVersion().send();
String clientVersion = web3ClientVersion.getWeb3ClientVersion();
log.info("wen3j subscribe --clientVersion-- :{} ", clientVersion);
//設(shè)置過濾條件 這個(gè)示例是監(jiān)聽最新的1000個(gè)塊
BigInteger blockNumber = web3j.ethBlockNumber().send().getBlockNumber()
.subtract(new BigInteger("1000"));
EthFilter ethFilter = new EthFilter(DefaultBlockParameter.valueOf(blockNumber),DefaultBlockParameterName.LATEST, "輸入合約地址");
//監(jiān)聽哪個(gè)事件，合約中的event寫了幾個(gè)參數(shù)，這里就寫幾個(gè)，類型對應(yīng)好
Event event = new Event("startEvent",
Arrays.<TypeReference<?>>asList(
new TypeReference<Address>(true) {},
new TypeReference<Address>(true) {},
new TypeReference<Uint256>(true) {},
new TypeReference<Uint256>(false) {},
new TypeReference<Uint256>(false) {},
new TypeReference<Uint256>(false) {}));
ethFilter.addSingleTopic(EventEncoder.encode(event));
subscribe = web3j.ethLogFlowable(ethFilter).subscribe(tx -> {
int newBlock = tx.getBlockNumber().intValue();
log.info("wen3j subscribe --newBlock-- :{} ", newBlock);
log.info("wen3j subscribe --tx-- :{} ", tx);
EventValues eventValues = staticExtractEventParameters(event, tx);
//定義接收參數(shù)(本示例使用的事件返回了6個(gè)，具體按自己合約來)
String address1 = "";String address2 = "";int uint1 = 0;
int uint2 = 0;int uint3 = 0;int uint4 = 0;
List<Type> indexedValues = eventValues.getIndexedValues();
if (ObjectUtils.isNotEmpty(indexedValues) && indexedValues.size() == 3) {
Type type1 = indexedValues.get(0);
address1 = type1.getValue().toString();
Type type2 = indexedValues.get(1);
address2 = type2.getValue().toString();
Type type3 = indexedValues.get(2);
uint1 = Integer.parseInt(type3.getValue().toString());
}
List<Type> nonIndexedValues = eventValues.getNonIndexedValues();
if (ObjectUtils.isNotEmpty(nonIndexedValues) && nonIndexedValues.size() == 3) {
Type type1 = nonIndexedValues.get(0);
uint2 = Integer.parseInt(type1.getValue().toString());
Type type2 = nonIndexedValues.get(1);
uint3 = Integer.parseInt(type2.getValue().toString());
Type type3 = nonIndexedValues.get(2);
uint4 = Integer.parseInt(type3.getValue().toString());
}
log.info("address1:{};address2:{};uint1:{};uint2:{};uint3:{};uint4:{}",address1, address2, uint1, uint2, uint3, uint4);
});
}catch (Exception e) {
e.printStackTrace();
}finally {
//關(guān)閉監(jiān)聽
if(ObjectUtils.isNotEmpty(subscribe) && !subscribe.isDisposed()){
subscribe.dispose();
}
}
}=========================分割線=========================
還有一種把web3j.ethLogFlowable(ethFilter).subscribe換成查詢的方法，做個(gè)記錄
把這段代碼文章來源：http://www.zghlxwxcb.cn/news/detail-483681.html
subscribe = web3j.ethLogFlowable(ethFilter).subscribe(tx -> {
//邏輯...
}換成文章來源地址http://www.zghlxwxcb.cn/news/detail-483681.html
List<EthLog.LogResult> resp = web3j.ethGetLogs(ethFilter).send().getLogs();
for (EthLog.LogResult logItem : resp) {
EthLog.LogObject tx = ObjectUtils.isNotEmpty(logItem.get()) ? (EthLog.LogObject) logItem.get() : null;
if(ObjectUtils.isEmpty(tx)){
return false;
}
//邏輯...
}到了這里，關(guān)于【web3j】java通過web3j監(jiān)聽并解析合約中的事件(event/emit)的文章就介紹完了。如果您還想了解更多內(nèi)容，請?jiān)谟疑辖撬阉鱐OY模板網(wǎng)以前的文章或繼續(xù)瀏覽下面的相關(guān)文章，希望大家以后多多支持TOY模板網(wǎng)！
