① 查询链上数据用的rpc（本示例是binance的，测试网可以使用：https://data-seed-prebsc-2-s2.binance.org:8545）
② 自己还要有一个测试链上部署好的合约，合约中要有一个方法emit了事件。
③ java依赖
<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、通过自己合约的abi和bin生成一个java文件，abi和bin可以在remix的compiler模块中获取，代码如下（这一步懒得做的可以跳过，在第二步传合约地址的时候，直接传一个字符串也行。这里就是顺手存一下这个方法，其实实际使用也是直接传的字符串，具体可以看页面最下方的”三、“）
/**
* 通过合约abi和bin获得java文件
*/
public void getJavaFileBySolidity(){
// 生成的java类名，同ABI文件同名，自动首字母大写
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、通过web3j查询事件，通过event和ethFilter增加过滤条件
public void testSub() {
Web3j web3j = Web3j.build(new HttpService("https://data-seed-prebsc-2-s2.binance.org:8545"));
//第一步生成的合约实体
Contract contract;
Disposable subscribe = null;
try {
Web3ClientVersion web3ClientVersion = web3j.web3ClientVersion().send();
String clientVersion = web3ClientVersion.getWeb3ClientVersion();
log.info("wen3j subscribe --clientVersion-- :{} ", clientVersion);
//设置谁调用合约
TransactionManager transactionManager = new ClientTransactionManager(web3j, "这里可以输入自己的钱包地址");
//加载智能合约（此处可以跳过，下面穿合约地址的地方 直接传字符串）
contract = Contract.load("你要监听的合约地址", web3j, transactionManager, ManagedTransaction.GAS_PRICE, org.web3j.tx.Contract.GAS_LIMIT);
//设置过滤条件 这个示例是监听最新的1000个块
BigInteger blockNumber = web3j.ethBlockNumber().send().getBlockNumber()
.subtract(new BigInteger("1000"));
EthFilter ethFilter = new EthFilter(DefaultBlockParameter.valueOf(blockNumber),DefaultBlockParameterName.LATEST, contract.getContractAddress());
//监听哪个事件，合约中的event写了几个参数，这里就写几个，类型对应好
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);
//定义接收参数(本示例使用的事件返回了6个，具体按自己合约来)
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 {
//关闭监听
if(ObjectUtils.isNotEmpty(subscribe) && !subscribe.isDisposed()){
subscribe.dispose();
}
}
} /**
* 解析log返回的data
* @param event 合约中定义的事件
* @param log 监听到的log
* @return 解析后的数据
*/
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、为了方便以后复制粘贴(不是)，最下面再传一个不生成合约的版本
public void testSub() {
Web3j web3j = Web3j.build(new HttpService("https://data-seed-prebsc-2-s2.binance.org:8545"));
//第一步生成的合约实体
Contract contract;
Disposable subscribe = null;
try {
Web3ClientVersion web3ClientVersion = web3j.web3ClientVersion().send();
String clientVersion = web3ClientVersion.getWeb3ClientVersion();
log.info("wen3j subscribe --clientVersion-- :{} ", clientVersion);
//设置过滤条件 这个示例是监听最新的1000个块
BigInteger blockNumber = web3j.ethBlockNumber().send().getBlockNumber()
.subtract(new BigInteger("1000"));
EthFilter ethFilter = new EthFilter(DefaultBlockParameter.valueOf(blockNumber),DefaultBlockParameterName.LATEST, "输入合约地址");
//监听哪个事件，合约中的event写了几个参数，这里就写几个，类型对应好
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);
//定义接收参数(本示例使用的事件返回了6个，具体按自己合约来)
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 {
//关闭监听
if(ObjectUtils.isNotEmpty(subscribe) && !subscribe.isDisposed()){
subscribe.dispose();
}
}
}=========================分割线=========================
还有一种把web3j.ethLogFlowable(ethFilter).subscribe换成查询的方法，做个记录
把这段代码文章来源：https://www.toymoban.com/news/detail-483681.html
subscribe = web3j.ethLogFlowable(ethFilter).subscribe(tx -> {
//逻辑...
}换成文章来源地址https://www.toymoban.com/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;
}
//逻辑...
}到了这里，关于【web3j】java通过web3j监听并解析合约中的事件(event/emit)的文章就介绍完了。如果您还想了解更多内容，请在右上角搜索TOY模板网以前的文章或继续浏览下面的相关文章，希望大家以后多多支持TOY模板网！
