Java实现区块链，成语接龙实例。
Java
package tech.topcoder.blockchain;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.sql.Timestamp;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.List;
import org.apache.commons.lang.StringUtils;
/**
* 区块链实现
*
*/
public class BlockChain {
public static List<Block> blockchain = new ArrayList<>();
static final String ipPrev = "192.168.8."; // 对局域网内的电脑进行扫描，找到最长的链，下载到本地
static final String dataFileDir = "c://blockchain"; // 本地存储路径
/**
* 创建新块
*/
public static Block newBlock(int index, String proof, String hash, Timestamp t, String sender, String recipient) {
Block block = null;
block = new Block(index, proof, hash, t, sender, recipient);
return block;
}
public static void init() {
System.out.println("===>初始化...");
File dirFile = new File(dataFileDir);
if (!dirFile.exists()) {
dirFile.mkdir();
// 往新创建的本地文件里面写一个创世块
try {
FileOutputStream fos = new FileOutputStream(dirFile "//data.txt");
fos.write((BlockChain.createFirstBlock().toInfoString() "\r\n").getBytes("UTF-8"));
fos.close();
} catch (Exception e) {
}
}
}
/**
* Hash一个块
*/
public static String hash(Block block) {
String hash = null;
String s = block.previousHash block.proof block.recipient block.sender block.createTime.toString();
hash = MD5(s);
return hash;
}
/**
* 创始块的创建，创世块是一个块，必须是固定的信息
*
* 逻辑上来说，只有在区块链产品的第一个用户第一次启动的时候，才会需要创建创世块
*/
public static Block createFirstBlock() {
try {
Timestamp t = new Timestamp(
new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").parse("2018-01-01 01:01:01").getTime());
return newBlock(0, "海阔天空", "*", t, "*", "*");
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
public static String MD5(String key) {
char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
try {
byte[] btInput = key.getBytes();
// 获得MD5摘要算法的 MessageDigest 对象
java.security.MessageDigest mdInst = java.security.MessageDigest.getInstance("MD5");
// 使用指定的字节更新摘要
mdInst.update(btInput);
// 获得密文
byte[] md = mdInst.digest();
// 把密文转换成十六进制的字符串形式
int j = md.length;
char str[] = new char[j * 2];
int k = 0;
for (int i = 0; i < j; i ) {
byte byte0 = md[i];
str[k ] = hexDigits[byte0 >>> 4 & 0xf];
str[k ] = hexDigits[byte0 & 0xf];
}
return new String(str);
} catch (Exception e) {
return null;
}
}
/**
* 验证当前的成语是否符合规则
*
* @param prev
* 前一个成语
* @param current
* 当前成语
*/
public static boolean validProof(String prev, String current) {
// 验证这个成语的头一个字是不是上一个成语的最后一个字
if (current.charAt(0) != prev.charAt(prev.length() - 1)) {
return false;
}
try {
String content = httpRequest(
"http://chengyu.t086.com/chaxun.php?q=" URLEncoder.encode(current, "gb2312") "&t=ChengYu",
5000, "gbk");
if (content == null || content.indexOf("没有找到与您搜索相关的成语") != -1 || content.indexOf("搜索词太长") != -1) {
return false;
} else {
return true;
}
} catch (Exception e) {
e.printStackTrace();
return false;
}
}
public static String httpRequest(String urlAddr, int connectTimeout) {
return httpRequest(urlAddr, connectTimeout, null);
}
public static String httpRequest(String urlAddr, int connectTimeout, String charset) {
InputStream iStream = null;
try {
URL url = new URL(urlAddr);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
if (connectTimeout > 0) {
connection.setConnectTimeout(connectTimeout);
}
if (connection.getResponseCode() == 200) {
iStream = connection.getInputStream();
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] buf = new byte[1024];
int len = 0;
while ((len = iStream.read(buf)) != -1) {
baos.write(buf, 0, len);
baos.flush();
}
if (charset != null) {
return baos.toString(charset);
} else {
return baos.toString("UTF-8");
}
}
} catch (Exception e) {
} finally {
if (iStream != null) {
try {
iStream.close();
} catch (Exception ex) {
}
}
}
return null;
}
/**
* 从网络读取区块链数据到本地文件
*/
public static void downloadData() {
File dirFile = new File(dataFileDir);
if (!dirFile.exists()) {
dirFile.mkdir();
// 往新创建的本地文件里面写一个创世块
try {
FileOutputStream fos = new FileOutputStream(dirFile "//data.txt");
fos.write((BlockChain.createFirstBlock().toInfoString() "\r\n").getBytes("UTF-8"));
fos.close();
} catch (Exception e) {
}
}
// 扫描周边的节点，找到最长的链，下载到本地
int lastLen = 0;
String lastChain = "";
for (int i = 0; i < 255; i ) {
String url = "http://" ipPrev i ":8080/blockchain/chain.jsp";
System.out.println(url);
String chain = httpRequest(url, 10);
if (chain != null && chain.length() > 0) {
chain = chain.trim();
System.out.println(chain);
String[] temp = StringUtils.splitByWholeSeparator(chain, "##");
if (temp.length > lastLen) {
lastLen = temp.length;
lastChain = chain;
}
}
}
try {
if (lastChain != "") {
FileOutputStream fos = new FileOutputStream(dirFile "//data.txt");
fos.write((lastChain.replace("##", "\r\n") "\r\n").getBytes("UTF-8"));
fos.close();
}
} catch (Exception e) {
}
}
public static String stringBlockChain() {
try {
FileInputStream fis = new FileInputStream(new File(dataFileDir "//data.txt"));
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] buf = new byte[1024];
int len = 0;
while ((len = fis.read(buf)) != -1) {
baos.write(buf, 0, len);
baos.flush();
}
fis.close();
String chain = baos.toString("UTF-8");
return StringUtils.join(chain.split("\r\n"), "##");
} catch (Exception e) {
return "";
}
}
public static void loadData() {
String chain = stringBlockChain();
String[] chains = StringUtils.splitByWholeSeparator(chain, "##");
blockchain.clear();
for (String s : chains) {
String[] temp = StringUtils.split(s, "#");
String[] time = StringUtils.split(temp[3], ".");
Timestamp t = new Timestamp(DateUtil.parse(time[0]).getTime());
Block block = newBlock(Integer.valueOf(temp[0]), temp[1], temp[2], t, temp[4], temp[5]);
blockchain.add(block);
}
}
public static void writeData() {
try {
List<String> chains = new ArrayList<>();
for (Block block : blockchain) {
chains.add(block.toInfoString());
}
FileOutputStream fos = new FileOutputStream(dataFileDir "//data.txt");
fos.write((StringUtils.join(chains, "\r\n") "\r\n").getBytes("UTF-8"));
fos.close();
} catch (Exception e) {
}
}
}
资源文件列表
BlockChain/.classpath , 1276
BlockChain/.project , 1086
BlockChain/.settings/.jsdtscope , 639
BlockChain/.settings/org.eclipse.core.resources.prefs , 162
BlockChain/.settings/org.eclipse.jdt.core.prefs , 430
BlockChain/.settings/org.eclipse.ltk.core.refactoring.prefs , 106
BlockChain/.settings/org.eclipse.m2e.core.prefs , 90
BlockChain/.settings/org.eclipse.m2e.wtp.prefs , 86
BlockChain/.settings/org.eclipse.wst.common.component , 597
BlockChain/.settings/org.eclipse.wst.common.project.facet.core.xml , 292
BlockChain/.settings/org.eclipse.wst.jsdt.ui.superType.container , 49
BlockChain/.settings/org.eclipse.wst.jsdt.ui.superType.name , 6
BlockChain/.settings/org.eclipse.wst.validation.prefs , 50
BlockChain/.settings/org.eclipse.wst.ws.service.policy.prefs , 87
BlockChain/pom.xml , 1617
BlockChain/src/main/java/tech/topcoder/blockchain/Block.java , 2615
BlockChain/src/main/java/tech/topcoder/blockchain/BlockChain.java , 9382
BlockChain/src/main/java/tech/topcoder/blockchain/DateUtil.java , 24868
BlockChain/src/main/java/tech/topcoder/blockchain/InitListener.java , 406
BlockChain/src/main/webapp/answer.jsp , 1517
BlockChain/src/main/webapp/chain.jsp , 309
BlockChain/src/main/webapp/detail.jsp , 1822
BlockChain/src/main/webapp/index.jsp , 1502
BlockChain/src/main/webapp/js/jquery-1.10.2.js , 93113
BlockChain/src/main/webapp/login.jsp , 614
BlockChain/src/main/webapp/sync.jsp , 566
BlockChain/src/main/webapp/WEB-INF/web.xml , 757
BlockChain/target/classes/tech/topcoder/blockchain/Block.class , 2749
BlockChain/target/classes/tech/topcoder/blockchain/BlockChain.class , 8925
BlockChain/target/classes/tech/topcoder/blockchain/DateUtil.class , 12757
BlockChain/target/classes/tech/topcoder/blockchain/InitListener.class , 679
BlockChain/target/m2e-wtp/web-resources/META-INF/MANIFEST.MF , 105
BlockChain/target/m2e-wtp/web-resources/META-INF/maven/tech.topcoder/blockchain/pom.properties , 239
BlockChain/target/m2e-wtp/web-resources/META-INF/maven/tech.topcoder/blockchain/pom.xml , 1617