区块链——java实现

简述

本文主要的内容试一次关于区块链的作业，本次作业中有很多地方和实际的区块链不符合，比如hash，本文实现的区块链只是用了区块本身的hash并没去区分，头部和数据部分。仅供参考学习。

介绍

内容有点儿多，详情看pdf吧。

    

以上三个类分别为 存储数据的类，区块类，区块链的实现类

TritonData主要存储的交易（事件）的记录

TritonBlock 主要字段有上一个区块的hash和本区块的hash值

TritonBlockChain 将所有区块组织成区块链

注意：在hash的过程中我使用的是自己写的hash函数（因为作业要求呀），实际在使用的使用请使用比较好的如sha-256等函数。

具体实现

TritonData

 import java.util.ArrayList;
 import java.util.LinkedList;
 import java.util.List;

 public class TritonData {

     private List<String> transactions;
     private int proofId;

     /**
      * Triton Data Constructor
      */
     public TritonData() {
         transactions = new ArrayList<String>();
         proofId = 1;
     }

     /*Constructor if specific values are specified*/
     public TritonData(int proofId, List<String> transactions) {
         this.transactions = transactions;
         this.proofId = proofId;
     }

     /*Get transactions*/
     public List<String> getTransactions() {
         return transactions;
     }

     /*Get proofId*/
     public int getProofId() {
         return proofId;
     }

     /*Print the data block*/
     public String toString() {
         StringBuilder sb = new StringBuilder();
         sb.append("DATA Start--------------------------------\n");
         sb.append("Proof of work:" + proofId + "\n");
         for (int i = 0; i < transactions.size(); ++i) {
             sb.append("Transaction " + i + "\n");
             sb.append("Transaction Content:" + transactions.get(i) + "\n");
         }
         sb.append("DATA End --------------------------------\n\n");
         return sb.toString();
     }
 }

TritonBlock

 import java.math.BigInteger;

 public class TritonBlock {
     /*Class variables, all the attributes of the block*/
     private int index;
     private long timestamp;
     private TritonData data;
     private String prev_hash;
     private String self_hash;

     /*Constructor, builds a block with passed in variables, then creates a hash for curr block*/
     public TritonBlock(int index, long timestamp, TritonData data, String prev_hash) {
         this.index = index;
         this.timestamp = timestamp;
         this.data = data;
         this.prev_hash = prev_hash;
         this.self_hash = hashBlock();
     }

     //使用CRC variant方式
     private String hashBlock() {
 //        BigInteger bigInteger=new BigInteger()
         BigInteger bigInteger = new BigInteger("0");
         for (String s : data.getTransactions()) {
             char[] arr = s.toCharArray();
             for (char c : arr) {
                 bigInteger = bigInteger.add(BigInteger.valueOf(c & 0xf8000000));
             }
         }
         bigInteger = bigInteger.add(BigInteger.valueOf(timestamp));
         bigInteger = bigInteger.add(BigInteger.valueOf(index));
         char[] arr = prev_hash.toCharArray();
         for (char c : arr) {
             bigInteger = bigInteger.add(BigInteger.valueOf(c & 0xf8000000));
         }
         return bigInteger.toString(16);
     }

     /*Get index*/
     public int getIndex() {
         return index;
     }

     /*Get timestamp*/
     public long getTimestamp() {
         return timestamp;
     }

     /*Get data block*/
     public TritonData getData() {
         return data;
     }

     /*Get previous hash*/
     public String getPrev_hash() {
         return prev_hash;
     }

     /*Get current hash*/
     public String getSelf_hash() {
         return self_hash;
     }

     /*Print the block*/
     public String toString() {
         StringBuilder sb = new StringBuilder();
         sb.append("TritonBlock " + index + "\n");
         sb.append("Index: " + index + "\n");
         sb.append("Timestamp: " + timestamp + "\n");
         sb.append("Prev Hash: " + prev_hash + "\n");
         sb.append("Hash: " + self_hash + "\n");
         sb.append(data.toString());
         return sb.toString();
     }
 }

TritonBlockChain

 import java.util.*;

 public class TritonBlockChain {

     private static final String MINE_REWARD = "1";
     /*Blockchain clas variable*/
     private List<TritonBlock> blockchain;

     /*Constructor, takes in genesis block data to start the blockchain*/
     public TritonBlockChain(int index, long timestamp, TritonData data, String prev_hash) {
         blockchain = new ArrayList<TritonBlock>();
         blockchain.add(new TritonBlock(index, timestamp, data, prev_hash));
     }

     /*Makes the next block after the proof of work from mining is finished*/
     public TritonBlock makeNewBlock(TritonBlock lastBlock, TritonData newData) {
         return new TritonBlock(lastBlock.getIndex() + 1,
                 System.currentTimeMillis(), newData, lastBlock.getPrev_hash());
     }

     /*Mines the transaction and creates the block to add to the blockchain*/
     public boolean beginMine(List<String> curTransactions) {
         if (curTransactions.isEmpty()) {
             return false;
         }
         int proofId = proofOfWork();
         curTransactions.add("Triton coined earned: " + MINE_REWARD);
 //      TritonData(int proofId, List<String> transactions)
         TritonData newData = new TritonData(proofId, curTransactions);
         TritonBlock lastBlock = blockchain.get(blockchain.size() - 1);
         TritonBlock newBlock = new TritonBlock(lastBlock.getIndex() + 1,
                 System.currentTimeMillis(), newData, lastBlock.getSelf_hash());
         blockchain.add(newBlock);
         return true;
     }

     /*Simple proof of work algorithm to prove cpu usage was used to mine block*/
     public int proofOfWork() {
         TritonBlock tb = blockchain.get(blockchain.size() - 1);
         int lastProofId = tb.getData().getProofId();
         //use loop
         int temp = Math.max(lastProofId, 13);
         ++temp;
         while (true) {
             if (temp % 13 == 0 && temp % lastProofId == 0) {
                 return temp;
             }
             ++temp;
         }
     }

     /*Prints current blockchain*/
     public String toString() {
         StringBuilder sb = new StringBuilder();
         sb.append("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n" +
                 "T R I T O N B L O C K C H A I N\n" +
                 "~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n\n");
         for (TritonBlock tb : blockchain) {
             sb.append(tb.toString());
         }
         return sb.toString();
     }

     /*Validates each block in the chain looking for any hash pointer descrepancies, which can point to a tampering problem*/
     public boolean validateChain() {
         for (int i = 1; i < blockchain.size(); ++i) {
             TritonBlock preBlock = blockchain.get(i - 1);
             TritonBlock cntBlock = blockchain.get(i);
             if (!cntBlock.getPrev_hash().equals(preBlock.getSelf_hash())) {
                 return false;
             }
         }
         return true;
     }

     /*Get blockchain*/
     public List<TritonBlock> getBlockchain() {
         return blockchain;
     }
 }

测试

 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.util.ArrayList;
 import java.util.List;
 import java.io.FileReader;
 import java.util.Random;
 import java.util.StringTokenizer;

 /*Sets up server, manages blockchains, takes in and acts on user input*/
 public class TritonMiner {

     private static final int BLOCK_SIZE = 2;

     public static void main(String[] args) throws IOException {
         /*Initialize the local blockchain*/
         long timestamp = System.currentTimeMillis();
         /*Created local blockchain and added genesis block*/
         TritonBlockChain blockchain = new TritonBlockChain(0, timestamp, new TritonData(), "0");
         /*Represents the queue for all transactions*/
         //read in trascatipn and put in transcation queue
         List<String> transaction_queue = new ArrayList<String>();
         loadTranscation(transaction_queue, "transaction/transaction_1.txt");

         List<String> currentTransaction = new ArrayList<String>();
         for (int i = 0; i < transaction_queue.size(); i++) {
             currentTransaction.add(transaction_queue.get(i));
             if (currentTransaction.size() == BLOCK_SIZE) {
                 //mine
                 blockchain.beginMine(new ArrayList<>(currentTransaction));
                 //reintilize
                 currentTransaction.clear();
             }
         }
         /*Print blockchain*/
         System.out.println(blockchain.toString());
         /*Validate the blockchain Mine*/
         System.out.println("This block chain is: "+blockchain.validateChain());
     }

     public static boolean loadTranscation(List<String> transaction_queue, String fname) {
         String line;
         BufferedReader inputStrem;
         StringTokenizer st;
         try {
             inputStrem = new BufferedReader(new FileReader(fname));
             while ((line = inputStrem.readLine()) != null) {
                 transaction_queue.add(line);
             }
         } catch (IOException e) {
             System.out.println (e.toString());
             System.out.println("Could not find file " + fname);
         }
         return true;
     } 

 }

结果

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
T R I T O N B L O C K C H A I N
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

TritonBlock 0
Index: 0
Timestamp: 1541995814844
Prev Hash: 0
Hash: 167061cdfbc
DATA Start--------------------------------
Proof of work:1
DATA End --------------------------------

TritonBlock 1
Index: 1
Timestamp: 1541995814851
Prev Hash: 167061cdfbc
Hash: 167061cdfc4
DATA Start--------------------------------
Proof of work:26
Transaction 0
Transaction Content:mary bob 10$
Transaction 1
Transaction Content:mary bob 12$
Transaction 2
Transaction Content:Triton coined earned: 1
DATA End --------------------------------

TritonBlock 2
Index: 2
Timestamp: 1541995814851
Prev Hash: 167061cdfc4
Hash: 167061cdfc5
DATA Start--------------------------------
Proof of work:52
Transaction 0
Transaction Content:simon tian 3$
Transaction 1
Transaction Content:tian ming 3$
Transaction 2
Transaction Content:Triton coined earned: 1
DATA End --------------------------------

This block chain is: true

总结

通过做这个作业，我收获很多：

1. 什么是挖矿，什么是矿工，他们如何挣钱。提供计算资源的人叫矿工，提供的机器叫矿机，挖矿就是通过记录交易来获取收益。
2. 本次作业也给了很多hash函数可以自己选择，比如我使用的CRC variant就是一个比较简单的hash函数（我一般就是用取余哈哈）
3. 通过自己的辛苦获得了大洋（很开心）