public String to_String( String str) {
                try
                {
                  str =new String(str.getBytes("GB2312"),"ISO-8859-1");
                }
                catch (Exception e)
                {
                        return str;
                }
        }

其实你检查一下要显示数据的JSP页面是不是写上
<%@page contentType="text/html;charset=gb2312"%>

如果写了，从数据库拿出来的值，比如
String aa = rs.getString(1);
把aa进行转换，不用非要把那个方法写的JAVABEAN里
aa = new String(aa.getBytes("ISO8859-1"));