实现原理：通过判断用户的登陆次数以及设置到期时间与系统现有时间对比，两者之中有一为非法则提示软件到期。 其中字符串对比通过MD5。 我想一开始把txt设置为隐藏模式，而试用期一过就删除txt文件，应该做到比较好的效果，欢迎讨论！ msn:yun15291li@hotmail.com QQ:17664554 package Admin.Control; import java.io.*; import java.security.MessageDigest; import Admin.Control.MD5; import java.util.*; /** *
Title: *****系统
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Description: ****系统
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Copyright: Copyright (c) 2004
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Company: 北京大学软件学院
* @author 云广 * @version 1.0 */ public class ControlValid { private final String REGISTERNUMBER; //加密的原始字符串 private String md5Number; //MD5加密后的字符串 private String writeContent; //需要写入文本的内容 private int loginTimesLimit; //登陆次数限制 private static int loginTimesTrue; //用户的实际登陆次数 private MD5 md5Object; //实例化MD5对象 private Calendar cal; //日期时间类 private int orderTime; //设定的系统到期时间 //构造方法进行初始化赋值 public ControlValid() { REGISTERNUMBER = "你想输入的正确验证字符串"; md5Object = new MD5(); loginTimesLimit = 99; loginTimesTrue = 0; writeContent = null; cal = Calendar.getInstance(); orderTime = 0; } //返回经过MD5加密过的字符串 public String returnMd5String() { try { //得到经过MD5加密过的字符串 md5Number = md5Object.MD5(REGISTERNUMBER); return md5Number; } catch (Exception e) { return null; } } //将字符串写进指定文本 public void writeFile() { try { String returnFileString; int returnLastLoginTimes = 0; //Calendar cal = Calendar.getInstance(); //测试获得系统时间 int currentDate = cal.get(cal.YEAR) + (cal.get(cal.MONTH) + 1) + cal.get(cal.DAY_OF_MONTH); //System.out.println(currentDate); //需要写入文本文件的字符串 String returnInitDate = this.readFile("InitDate.txt"); orderTime = Integer.parseInt(returnInitDate); returnFileString = this.readFile("ControlValid.txt"); //获得换行的位置 int pos = returnFileString.indexOf("\n"); if (pos != -1) { returnLastLoginTimes = Integer.parseInt(returnFileString.substring(pos+1, pos+3)); } loginTimesTrue = returnLastLoginTimes; this.setLoginTimesTrue(); //根据日期和用户登陆次数判断写入的字符串 if ( (currentDate < orderTime) && (this.getLoginTimesTrue() < loginTimesLimit)) { //writeContent = this.returnMd5String() + "\n" + this.getLoginTimesTrue(); writeContent = this.returnMd5String() + "\r" + this.getLoginTimesTrue(); } else { //随机产生一数字进行输入 Random ranInt = new Random(); //int randomInt = ; writeContent = String.valueOf(ranInt.nextInt(10000000))+ "\r" + this.getLoginTimesTrue(); } //将加密过的字符串写入文本文件 File f = new File("ControlValid.txt"); if (!f.exists()) { f.createNewFile(); } DataOutputStream outFile = new DataOutputStream( new BufferedOutputStream( new FileOutputStream(f))); byte[] byteWriteContent = writeContent.getBytes(); outFile.write(byteWriteContent); outFile.close(); } catch (Exception e) { System.out.println(e.getMessage()); } } //在指定文本中读取数据 public String readFile(String fileName) { String sLine = "",sResult = ""; boolean testFirstLine=true; try { DataInputStream inFile = new DataInputStream( new BufferedInputStream( new FileInputStream(fileName))); while ( (sLine = inFile.readLine()) != null) { if (testFirstLine) { sResult = sLine; testFirstLine=false; } else { sResult += "\n" + sLine; } } inFile.close(); return sResult; } catch (Exception e) { return null; } } //注册字符串与文本中返回的字符串对比 public boolean ContractRegisterString() { String returnFileString; String md5String; String returnMd5String = ""; int i = 0; returnFileString = this.readFile("ControlValid.txt"); //获得换行的位置 int pos = returnFileString.indexOf("\n"); if (pos != -1) { returnMd5String = returnFileString.substring(0,pos); } md5String = this.returnMd5String(); //System.out.println(returnFileString); //得到经过MD5加密过的字符串 if (md5String.equals(returnMd5String)) { return true; } else { return false; } } //用户每登陆一次就把实际登陆次数变量加1 public void setLoginTimesTrue() { loginTimesTrue += 1; } //返回用户实际登陆次数 public static int getLoginTimesTrue() { return loginTimesTrue; } //主方法测试用 public static void main(String[] args) { // int i = 0; ControlValid controlValid = new ControlValid(); //设置登陆次数 // for (i = 0; i < 25; i++) { // controlValid.setLoginTimesTrue(); // } //写入内容到文件 controlValid.writeFile(); controlValid.ContractRegisterString(); } }