JSP 参数的字符编码问题（关于UFT-8/GB2312/BIG5）

public String ciso(String str1){
             String str="";
             try{
                  str=new String(str1.getBytes("gb2312"),"ISO8859_1");
                 }
             catch(Exception e)
                {str=str1;}
             return str;
             }