举例，比如合约中事件如下：（以下内容均使用该事件例子）
event Transfer(address indexed from, address indexed to, uint256 value);
当上述事件在合约中调用后，我们通过其交易hash获取交易信息。从以太坊得到一条交易信息的方式有两种：
eth_getTransactionByHash
返回的具体信息如下
{
"jsonrpc": "2.0",
"id": 1,
"result": {
"blockHash": "0xb0d0e3b6c5e59b7b3e7e16701f6d6cb0c3c93487415b03839e88b3f7a241c528",
"blockNumber": "0xd19505",
"from": "0xb8262c6a2dcabd92a77df1d5bd074afd07fc5829",
"gas": "0x10e3d",
"gasPrice": "0x274daee580",
"maxFeePerGas": "0x2d48ddd9f1",
"maxPriorityFeePerGas": "0x6ccc91d0",
"hash": "0xae2a33da8396a6bc40e874b0f32b9967113a3dbf071ab1290c44c62d86873d36",
"input": "0xa9059cbb000000000000000000000000dac17f958d2ee523a2206206994597c13d831ec7000000000000000000000000000000000000000000000000000000016512c902",
"nonce": "0x14",
"to": "0xdac17f958d2ee523a2206206994597c13d831ec7",
"transactionIndex": "0x71",
"value": "0x0",
"type": "0x2",
"accessList": [],
"chainId": "0x1",
"v": "0x1",
"r": "0xa1d7455286525df11602aab34e9e8ab21b092e2c7853a0d6beca0dfb2a78b2e8",
"s": "0x75a485b8c378173a829b27a2e55312311fdb33c68ae65f4c74e5f9cc0a748e0d"
}
}
web3调用中文文档：https://www.wenjiangs.com/doc/pr2nvcat
curl 调用：
curl -s -H "Content-Type: application/json" -X POST --data '{"jsonrpc":"2.0","method":"eth_getTransactionByHash","params":["0xae2a33da8396a6bc40e874b0f32b9967113a3dbf071ab1290c44c62d86873d36"],"id":1}' http://127.0.0.1:8545
eth_getTransactionReceipt
{
"jsonrpc": "2.0",
"id": 1,
"result": {
"blockHash": "0xb0d0e3b6c5e59b7b3e7e16701f6d6cb0c3c93487415b03839e88b3f7a241c528",
"blockNumber": "0xd19505",
"contractAddress": null,
"cumulativeGasUsed": "0x6c847e",
"effectiveGasPrice": "0x274daee580",
"from": "0xb8262c6a2dcabd92a77df1d5bd074afd07fc5829",
"gasUsed": "0xa169",
"logs": [
{
"address": "0xdac17f958d2ee523a2206206994597c13d831ec7",
"topics": [
"0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef",
"0x000000000000000000000000b8262c6a2dcabd92a77df1d5bd074afd07fc5829",
"0x000000000000000000000000dac17f958d2ee523a2206206994597c13d831ec7"
],
"data": "0x000000000000000000000000000000000000000000000000000000016512c902",
"blockNumber": "0xd19505",
"transactionHash": "0xae2a33da8396a6bc40e874b0f32b9967113a3dbf071ab1290c44c62d86873d36",
"transactionIndex": "0x71",
"blockHash": "0xb0d0e3b6c5e59b7b3e7e16701f6d6cb0c3c93487415b03839e88b3f7a241c528",
"logIndex": "0xa0",
"removed": false
}
],
"logsBloom": "0x00000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000010000000000000000000000000000000000000000000000000000000008000000000080000000000000000000000000000000000000000000000000000000000000000000200000000000000010000000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000080000000000000000000000000000000000000004000000002000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000000000000000000000000200",
"status": "0x1",
"to": "0xdac17f958d2ee523a2206206994597c13d831ec7",
"transactionHash": "0xae2a33da8396a6bc40e874b0f32b9967113a3dbf071ab1290c44c62d86873d36",
"transactionIndex": "0x71",
"type": "0x2"
}
}
注意：getTransaction返回结果中包含input，而getTransactionReceipts返回结果中包含logs。
若input=0x则为非合约调用，否则为合约方法调用。
以合约方法function transfer(address to, uint tokens) 为例;
input数据分为3个部分：
例如：a9059cbb，具体可参见：以太坊智能合约各方法对应的签名编码
例如：000000000000000000000000abcabcabcabcabcabcabcabcabcabcabcabcabca
例如：0000000000000000000000000000000000000000000000000de0b6b3a7640000
所有这些加在一起就是交易数据：
a9059cbb000000000000000000000000abcabcabcabcabcabcabcabcabcabcabcabcabca0000000000000000000000000000000000000000000000000de0b6b3a7640000
如下为处理input的逻辑（web3.js）：
if(transanctionInput=='0x'){
// 非合约调用
return;
}else{
retJson['function'] = {'funcName':null,'inputs':null,'outputs':null,'exeResult':null};
var funcArr = mxxContractABI.filter(function (per) {
return per.signature == funcHash ;
});
if(funcArr!==null&&funcArr.length>0){ // 得到方法名
if(funcArr[0].hasOwnProperty("name") && funcArr[0].name!==null){
retJson['function']['funcName'] = funcArr[0].name;
}
if(funcArr[0].hasOwnProperty("inputs") && funcArr[0].inputs!==null){
funcArr[0].inputs.map(function (res) { // 得到方法inputs（输入）
inputs.push(res.type);
});
retJson['function']['inputs'] = inputs;
}
if(funcArr[0].hasOwnProperty("outputs")&& funcArr[0].outputs!==null){
funcArr[0].outputs.map(function (res) {// 得到方法outputs（输出）
outputs.push(res.type);
});
retJson['function']['outputs']= outputs;
}
}
status = transanctionReceipt.status;
if(status == '0x1'){
//执行成功
retJson['function']['exeResult'] = 'Successfully Executed';
}else {
retJson['function']['exeResult'] = 'Failed Executed';
}
智能合约通过【事件】来产生【日志】,日志存储的Gas费用要比合约的存储便宜很多（日志每个字节花费8个Gas，而合约存储是每32个字节20000个Gas）。想要通过合约向用户返回数据，则需将数据以事件的形式传给用户，用户拿到transactionReceipt后解析log，log.args.x拿到数据。Input只能拿到调用合约以及function的信息，而不能拿到function运行后内部产生的事件（事件不一定和function拥有相同名称和参数）。
logs解析步骤代码（web3.js）
web3SolidityEvent = require('./node_modules/truffle-contract/node_modules/web3/lib/web3/event.js');
var transferErc20Json = {
"anonymous": false,
"inputs": [{
"indexed": true,
"name": "from",
"type": "address"
}, {
"indexed": true,
"name": "to",
"type": "address"
}, {
"indexed": false,
"name": "value",
"type": "uint256"
}],
"name": "Transfer",
"type": "event",
"signature": "0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef"
};
var transferEvent = new web3SolidityEvent(null, config.transferErc20Json, null);
async function processReceiptLogs(transactionReceipt){
let ethErc20LogRecord = null;
let logs = transactionReceipt.logs;
for (let i = 0; i < logs.length; i++) {
let isContractExists = await redis.contractExists(logs[i].address);
if (isContractExists === true) {//判断redis中是否存在
//是否是ERC-20 transfer事件，用topics来判断
if(logs[i].topics[0] === transferErc20Json.signature){
var log = await transferEvent.decode(logs[i]);
logger.debug(prefixOfLogger +'--'+'transferEvent decode result:',log);
ethErc20LogRecord = {
txHash: log.transactionHash,
logIndex: log.logIndex,
contractAddress: log.address,
fromAddress: log.args.from ,
toAddress: log.args.to,
value: log.args.value.div(Math.pow(10, 18)).toString(),
data: log.args.data,
blockNumber: log.blockNumber,
removed: log.removed
};
db.setCreateAndUpdateTime(ethErc20LogRecord);
let createLogRecord = await tables.EthErc20Log.create(ethErc20LogRecord);
}
}
}
取出transactionReceipt中logs;
取出logs中一条log;
使用event.js得到transferEvent，然后用transferEvent的decode方法解析log；
若是公链转币,以太坊转账，则交易回执转logs为空。
若是执行合约的事件，则logs不为空，故ERC-20代币转账，会执行合约Transfer方法，产生logs
Topics[]是一个数组
sha3('Transfer(address,address,uint256)') => 0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef
Topics[1] ：是address类型的from参数补齐64位结果（合约交易中真正的from地址）
Topics[2] ：是address类型to参数补齐64位的结果（合约交易中真正的to地址）
由于value没有indexed标记，因此放在data中，将value的值转化为16进制并补齐64位
Transfer事件的第一个和第二个参数被标记为indexed, 因此他们的值被放在 topics array 中. 由于value参数没有标记为indexed, 所以value值被放在data字段. 如果事件中有多个字段未标记为indexed， 那么他们的值都会被记录在data字段中。
事件规则
topic[0] : keccak(“Transfer(address,address,uint256)”)，对事件的字符做keccak散列运算
topic[1] : address类型from参数补齐64位
topic[2] : address类型to参数补齐64位
data: 没有indexed标记的value的值转化为16进制，并补齐64位
注意：
事件中的参数类型需要写成完整的，如Transfer(address,address,uint)就不行，需要将uint改为uint256。
{
"jsonrpc": "2.0", //RPC版本号，2.0
"id": 1, //RPC请求编号
"result": { //调用结果，为交易收据，主要包含如下字段：
"blockHash": "0xb0d0e3b6c5e59b7b3e7e16701f6d6cb0c3c93487415b03839e88b3f7a241c528", // 区块哈希
"blockNumber": "0xd19505", // 区块高度
"contractAddress": null, //合约地址
"cumulativeGasUsed": "0x6c847e", //当前交易执行后累计花费的gas总值
"effectiveGasPrice": "0x274daee580", //当前交易预计使用的gas总值
"from": "0xb8262c6a2dcabd92a77df1d5bd074afd07fc5829", //当前交易发送者的地址
"gasUsed": "0xa169", //执行当前这个交易单独花费的gas
"logs": [ //这个交易产生的日志对象数组
{
"address": "0xdac17f958d2ee523a2206206994597c13d831ec7", //当前交易被调用的合约地址
"topics": [
"0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef", //keccak(Transfer(address,address,uint256))， //合约事件签名哈希值，对事件的字符做keccak散列运算
"0x000000000000000000000000b8262c6a2dcabd92a77df1d5bd074afd07fc5829", //当前交易from的地址
"0x000000000000000000000000dac17f958d2ee523a2206206994597c13d831ec7" //当前交易to的地址
],
"data": "0x000000000000000000000000000000000000000000000000000000016512c902", //包含日志的非索引参数
"blockNumber": "0xd19505", // 区块高度
"transactionHash": "0xae2a33da8396a6bc40e874b0f32b9967113a3dbf071ab1290c44c62d86873d36", //交易的哈希值,32字节
"transactionIndex": "0x71" //交易在区块里面的序号，当交易为pending时为空
"blockHash": "0xb0d0e3b6c5e59b7b3e7e16701f6d6cb0c3c93487415b03839e88b3f7a241c528",
"logIndex": "0xa0", //块中日志索引位置的整数，当交易为pending时日志为空。
"removed": false //当由于链重组而删除日志时，为True。 如果它是一个有效的日志则为False。
}
],
//bloom过滤器，当交易为pending时日志为空
"logsBloom": "0x00000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000010000000000000000000000000000000000000000000000000000000008000000000080000000000000000000000000000000000000000000000000000000000000000000200000000000000010000000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000080000000000000000000000000000000000000004000000002000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000000000000000000000000200",
"status": "0x1", //交易事务状态，1(成功)或0(失败)
"to": "0xdac17f958d2ee523a2206206994597c13d831ec7", //当前交易被调用的合约地址
"transactionHash": "0xae2a33da8396a6bc40e874b0f32b9967113a3dbf071ab1290c44c62d86873d36", //交易的哈希值,32字节
"transactionIndex": "0x71", //交易在区块里面的序号，当交易为pending时为空
"type": "0x2"
}
}
getTransactionReceipt返回信息字段详情可参考：https://infura.io/docs/ethereum/json-rpc/eth-getTransactionReceipt
以上，就是今天分享的全部内容了。
希望大家通过以上方式可以解决自己的实际需求，解决自己目前所遇到的问题。
如果在查看过程中有任何疑问，可以扫描下面的二维码，添加我的个人微信，备注：地区-职业方向-昵称，欢迎来撩，加入区块链技术交流群，与更多的区块链技术大佬学习交流。
原创不易，码字不易。 觉得这篇文章对你有点用的话，麻烦你为本文点个赞，留言或转发一下，因为这将是我输出更多优质文章的动力，感谢！