utils.java

用JSP实现毕业设计选题系统,老师在网上出题,学生通过WEB来选题等功能

/**
 * 
 */
package util;
import java.io.*;
import java.util.*;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * @author 朱定芬
 *
 */
public class Utils 
{
    private MessageDigest md5 = null;
    private StringBuffer digestBuffer = null;

    //下面的方法是对用户注册时的密码进行加密,但不能解密    	
	public Utils() throws NoSuchAlgorithmException
	{
        md5 = MessageDigest.getInstance("MD5");
        digestBuffer = new StringBuffer();		
	}
    public String md5crypt(String s) 
    {
        digestBuffer.setLength(0);
        byte abyte0[] = md5.digest(s.getBytes());
        for(int i = 0; i < abyte0.length; i++)
            digestBuffer.append(toHex(abyte0[i]));
        return digestBuffer.toString();
    }
    public String toHex(byte one)
    {
      String HEX="0123456789ABCDEF";
      char[] result=new char[2];
      result[0]=HEX.charAt((one & 0xf0) >> 4);
      result[1]=HEX.charAt(one & 0x0f);
      String mm=new String(result);
      return mm;
    }
    
    //下面是把字符转换成浏览器能识别的HTML字符    
	public String ChrToHtml(String str)
	{   
      if(str==null||str.equals(""))  
        { 
            str="";
        }
      else
        {  
          str=str.replaceAll("&","&amp;");  
          str=str.replaceAll("<","&lt;");  
          str=str.replaceAll(">","&gt;");  
          str=str.replaceAll(" ","&nbsp;");  
          str=str.replaceAll("\n","<br>");     
        }  
      return  str;
	}
	
    //下面是把浏览器能够识别HTML字符转换成正常字符    
	public String HtmlToChr(String str)
	{   
      if(str==null||str.equals(""))  
        { 
            str="";
        }
      else
        {  
          str=str.replaceAll("&amp;","&");  
          str=str.replaceAll("&lt;","<");  
          str=str.replaceAll("&gt;",">");  
          str=str.replaceAll("&nbsp;"," ");  
          str=str.replaceAll("<br>","\n");     
        }  
      return  str;
	}
	
	//下面的方法用于返回系统日期
	public String getDate()
	{
		Date dt=new Date();
		String str=dt.toLocaleString();
		return str;
	}
	
    //下面是转换编码为ISO-8859-1	
	public String StrToISO(String str) throws UnsupportedEncodingException
	{
		if(str==null||str.equals(""))
        { 
            str="";
        }
        else
        {
        	byte b[]=str.getBytes("ISO-8859-1");
        	str=new String(b);
        }
      return str;			
	}
}