使用web3j工具生成java版本的智能合約

這裏須要使用的環境 web3j，nodejs

• 安裝編譯sol工具

$ npm install -g solc

• 保存爲hello.sol文件到本地

pragma solidity 0.4.19;  
contract hello {  
function main(uint a) constant returns (uint b)   
    {  
        uint result = a * 8;  
        return result;  
    }  
}  

• 編譯sol文件

$ solcjs <sol文件目錄>   --optimize  --bin --abi --output-dir <輸出目錄>

//demo
$ solcjs F:\\hello.sol   --optimize  --bin --abi --output-dir F:\\

出現這種錯誤

Failed to write F:\F_\hello_sol_hello.bin: Error: ENOENT: no such file or directory, open 'F:\F_\hello_sol_hello.bin'
Failed to write F:\F_\hello_sol_hello.abi: Error: ENOENT: no such file or directory, open 'F:\F_\hello_sol_hello.abi'

這裏有個坑，就是使用solcjs 編譯智能合約文件輸出到目錄會有一個文件夾，這個須要手動建立，我這裏輸出目錄到F:\\ 可是它仍是要輸出到F:\\F_\ 下，這裏的F_文件夾須要咱們建立！

• 編譯成功,記錄下bin 和 abi後綴的文件
• 使用web3j工具生成java版本的智能合約
• web3j 命令行工具下載

$ web3j solidity generate <編譯的bin文件地址> <編譯的abi文件地址> -o <輸出目錄> -p <java包名>
//demo
$ web3j solidity generate F:\F_\hello_sol_hello.bin F:\F_\hello_sol_hello.abi -o E:\etheth\src\main\java -p xyz.lihang.demo.eth.sol

　PS：使用web3j命令，須要進入https://github.com/web3j/web3j/releases/tag/v3.3.1網站，下載web3j-3.3.1.tar，並解壓。

　　　進入目錄bin下，在此目錄命令行執行web3j，不然web3j bash命令不存在

• 生成成功

package xyz.lihang.demo.eth.sol;

import java.math.BigInteger;
import java.util.Arrays;
import org.web3j.abi.TypeReference;
import org.web3j.abi.datatypes.Function;
import org.web3j.abi.datatypes.Type;
import org.web3j.abi.datatypes.generated.Uint256;
import org.web3j.crypto.Credentials;
import org.web3j.protocol.Web3j;
import org.web3j.protocol.core.RemoteCall;
import org.web3j.tx.Contract;
import org.web3j.tx.TransactionManager;

/**
 * <p>Auto generated code.
 * <p><strong>Do not modify!</strong>
 * <p>Please use the <a href="https://docs.web3j.io/command_line.html">web3j command line tools</a>,
 * or the org.web3j.codegen.SolidityFunctionWrapperGenerator in the 
 * <a href="https://github.com/web3j/web3j/tree/master/codegen">codegen module</a> to update.
 *
 * <p>Generated with web3j version 3.2.0.
 */
public class Hello_sol_hello extends Contract {
    private static final String BINARY = "60606040523415600e57600080fd5b609a8061001c6000396000f300606060405260043610603e5763ffffffff7c0100000000000000000000000000000000000000000000000000000000600035041663ab3ae25581146043575b600080fd5b3415604d57600080fd5b60566004356068565b60405190815260200160405180910390f35b600802905600a165627a7a723058200cc51f5dad45190b24189d9f8ff836d704bcebc9862cfd669e054b8c8f19f66c0029";

    protected Hello_sol_hello(String contractAddress, Web3j web3j, Credentials credentials, BigInteger gasPrice, BigInteger gasLimit) {
        super(BINARY, contractAddress, web3j, credentials, gasPrice, gasLimit);
    }

    protected Hello_sol_hello(String contractAddress, Web3j web3j, TransactionManager transactionManager, BigInteger gasPrice, BigInteger gasLimit) {
        super(BINARY, contractAddress, web3j, transactionManager, gasPrice, gasLimit);
    }

    public RemoteCall<BigInteger> main(BigInteger a) {
        Function function = new Function("main", 
                Arrays.<Type>asList(new org.web3j.abi.datatypes.generated.Uint256(a)), 
                Arrays.<TypeReference<?>>asList(new TypeReference<Uint256>() {}));
        return executeRemoteCallSingleValueReturn(function, BigInteger.class);
    }

    public static RemoteCall<Hello_sol_hello> deploy(Web3j web3j, Credentials credentials, BigInteger gasPrice, BigInteger gasLimit) {
        return deployRemoteCall(Hello_sol_hello.class, web3j, credentials, gasPrice, gasLimit, BINARY, "");
    }

    public static RemoteCall<Hello_sol_hello> deploy(Web3j web3j, TransactionManager transactionManager, BigInteger gasPrice, BigInteger gasLimit) {
        return deployRemoteCall(Hello_sol_hello.class, web3j, transactionManager, gasPrice, gasLimit, BINARY, "");
    }

    public static Hello_sol_hello load(String contractAddress, Web3j web3j, Credentials credentials, BigInteger gasPrice, BigInteger gasLimit) {
        return new Hello_sol_hello(contractAddress, web3j, credentials, gasPrice, gasLimit);
    }

    public static Hello_sol_hello load(String contractAddress, Web3j web3j, TransactionManager transactionManager, BigInteger gasPrice, BigInteger gasLimit) {
        return new Hello_sol_hello(contractAddress, web3j, transactionManager, gasPrice, gasLimit);
    }
}

必定要注意合約調用後進行挖礦，這樣才能網絡確認，才能使用合約