codefilter.java

jsp网页中的过滤器

package com.qionghai.formatutil;

//定义一个类CodeFilter
public class CodeFilter
{
  public CodeFilter()
  {}
  //特殊字符转为Html
  public static String toHtml(String s)
  {
	if(s == null)
	{
	  s = "";
	  return s;
	}
	s = Replace(s.trim(),"&","&");
	s = Replace(s.trim(),"<","&lt;");
	s = Replace(s.trim(),">","&gt;");
	s = Replace(s.trim(),"\t","    ");
	s = Replace(s.trim(),"\r\n","\n");
	s = Replace(s.trim(),"\n","<br>");
	s = Replace(s.trim(),"  "," &nbsp;");
	s = Replace(s.trim(),"'","&#39;");
	s = Replace(s.trim(),"\\","&#92;");
	return s;
  }

		//逆转换...........
  public static String unHtml(String s)
  {
	s = Replace(s,"<br>","\n");
	s = Replace(s,"&nbsp;"," ");
	return s;
  }

  //Replace
  public static String Replace(String source,String oldString,String newString)
  {
	StringBuffer output = new StringBuffer();
	int lengthOfsource = source.length();//源字符串长度
	int lengthOfold = oldString.length();//老字符串长度

	int posStart = 0;//开始搜索位置
	int pos;         //搜索到的老字符串的位置

	//source.indexOf(oldString,posStart)检索某子串在字符串postStart以后第一次出现的位置,如果未找到就返回一个-1。
	while((pos = source.indexOf(oldString,posStart)) >= 0)
	{   //得到字符串的位置(eg:如果有<br>就执行，没有就跳出，不要处理。)
		//将以posStart起始以pos-1结束之间的内容拷贝到另一个字符串中。因为posStar从0开始的。
	   output.append(source.substring(posStart,pos));//append方法将文本添加到当前StringBuffer对象内容的结尾。
	   output.append(newString);//替换成新字符串
	   posStart = pos + lengthOfold;//位置也变为找到了之后的位置,pos为得到第一次出现字符的位置，lengthold为字符的长度
	}

	if(posStart < lengthOfsource)
	{
	   //source.substring(posStart)以lengthOfsource开始的字符串拷贝到列一个字符串中
	  output.append(source.substring(posStart));
	}
	   //这个方法将其内容转换成一个可以被用于输出的字符串对象。它允许操作对应的文本用于输出或数据存储。
	   return output.toString();
   }
}