下面是 "Spring Boot 整合 Fisco Bcos的案例分析(区块链)" 的完整攻略。
Fisco Bcos 是由中国金融专家打造的一个区块链平台,具有高可用性、高扩展性和高安全性。
在本地安装 Fisco Bcos,详细步骤可以参考 Fisco Bcos 的官方文档:快速入门。
通过 Spring Initializr 创建一个 Spring Boot 项目,并添加 Fisco Bcos 相关的依赖:
<dependency>
<groupId>org.fisco-bcos</groupId>
<artifactId>web3sdk</artifactId>
<version>2.7.0.3-SNAPSHOT</version>
</dependency>
<dependency>
<groupId>org.fisco-bcos</groupId>
<artifactId>web3j-spring-boot-starter</artifactId>
<version>2.7.0.1-SNAPSHOT</version>
</dependency>
在 application.properties
中配置 Fisco Bcos 相关信息,比如节点 IP 地址和端口号等。
web3sdk.url=http://127.0.0.1:8545
web3sdk.gasPrice=30000000
web3sdk.gasLimit=30000000
web3sdk.chainId=1
web3sdk.groupId=1
使用 Solidity 开发智能合约。下面是一个简单的示例:
pragma solidity ^0.4.24;
contract SampleContract {
uint256 public value;
event SetValueEvent(uint256 _value);
function setValue(uint256 _value) public {
value = _value;
emit SetValueEvent(_value);
}
}
使用 Remix 进行合约编译、生成ABI和二进制代码,并将它们写入src/main/resources/contract
目录下的文件中。
在使用Web3SDK
连接区块链后,可以通过 ContractLoader
进行合约的部署,并获取智能合约对象。
@Autowired
Web3j web3j;
@Resource
ContractLoader contractLoader;
String contractAddress = contractLoader.deployAndGetAddress("SampleContract", "sample_contract.abi", "sample_contract.bin", args);
SampleContract sampleContract = contractLoader.load(
contractAddress, SampleContract.class, "sample_contract.abi", "sample_contract.bin");
在 Java 中使用 Web3j
对象连接到 Fisco Bcos 节点,并通过 load
方法加载已经部署的智能合约。然后就可以调用智能合约了。
sampleContract.setValue(new BigInteger("123456789"));
BigInteger value = sampleContract.value().send();
假设要在区块链上存储商品信息,可以通过 Solidity 开发一个智能合约:
pragma solidity ^0.4.24;
contract ProductContract {
struct Product {
uint256 id;
string name;
uint256 price;
uint256 count;
}
mapping (uint256 => Product) private products;
uint256 private totalCount = 0;
event CreateProductEvent(uint256 indexed id, string name, uint256 price, uint256 count);
function createProduct(string name, uint256 price, uint256 count) public {
totalCount = totalCount + 1;
products[totalCount] = Product(totalCount, name, price, count);
emit CreateProductEvent(totalCount, name, price, count);
}
function getProductCount() public view returns (uint256) {
return totalCount;
}
function getProductById(uint256 productId) public view
returns (string name, uint256 price, uint256 count) {
Product storage product = products[productId];
name = product.name;
price = product.price;
count = product.count;
}
}
然后在 Spring Boot 项目中调用智能合约方法,通过输入商品信息,调用 createProduct
方法即可将商品信息存储到区块链上:
@Autowired
ProductContract productContract;
public void createProduct(Product product) throws Exception {
productContract.createProduct(
product.getName(),
product.getPrice(),
product.getCount());
}
通过调用 getProductById
方法,即可从区块链上获取指定商品的信息:
@Autowired
ProductContract productContract;
public Product getProductById(int productId) throws Exception {
Tuple3<String, BigInteger, BigInteger> result = productContract.getProductById(
new BigInteger(String.valueOf(productId))).send();
return new Product(
Integer.parseInt(result.getValue1()),
result.getValue2(),
Integer.parseInt(result.getValue3()),
Integer.parseInt(result.getValue4()));
}
面向合同的投票系统可选择在链上记录投票结果,提高投票的公平性和可信度。
在智能合约中定义一个投票合约:
pragma solidity ^0.4.24;
contract VoteContract {
struct Voter {
address account;
bool voted;
uint256 voteIndex;
}
struct Vote {
string name;
uint256 count;
}
mapping (address => Voter) private voters;
Vote[] private votes;
event AddVoteEvent(uint256 indexed voteIndex, string name, uint256 count);
function addVote(string name) public {
votes.push(Vote(name, 0));
uint256 voteIndex = votes.length - 1;
emit AddVoteEvent(voteIndex, name, 0);
}
function vote(uint256 voteIndex) public {
Voter storage voter = voters[msg.sender];
require(!voter.voted);
require(voteIndex < votes.length);
voter.voted = true;
voter.voteIndex = voteIndex;
votes[voteIndex].count = votes[voteIndex].count + 1;
}
function getVotes() public view returns (string[], uint256[]) {
uint256 votesCount = votes.length;
string[] memory names = new string[](votesCount);
uint256[] memory counts = new uint256[](votesCount);
for (uint256 i = 0; i < votesCount; i++) {
names[i] = votes[i].name;
counts[i] = votes[i].count;
}
return (names, counts);
}
}
在 Spring Boot 项目中,调用智能合约方法,添加候选人和投票结果:
@Autowired
VoteContract voteContract;
public void addVote(String name) throws Exception {
voteContract.addVote(name);
}
public void vote(int index) throws Exception {
voteContract.vote(BigInteger.valueOf(index));
}
在 Spring Boot 项目中,调用智能合约方法,获取投票结果信息:
@Autowired
VoteContract voteContract;
public List<VoteResult> getVotes() throws Exception {
List<VoteResult> result = new ArrayList<VoteResult>();
Tuple2<String[], BigInteger[]> tuple = voteContract.getVotes().send();
String[] voteNames = tuple.getValue1();
BigInteger[] voteCounts = tuple.getValue2();
for (int i = 0; i < voteNames.length; i++) {
result.add(new VoteResult(voteNames[i], voteCounts[i].intValue()));
}
return result;
}
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