诡异的mysql latin1编码

Mysql 的latin1 不等于标准的latin1（iso-8859-1） 和cp1252,比iso-8859-1多了0x80-0x9f字符，比cp1252多了0x81,0x8d,0x8f,0x90,0x9d 一共5个字符。

http://dev.mysql.com/doc/refman/5.0/en/charset-we-sets.html

latin1 is the default character set. MySQL's latin1 is the same as the Windows cp1252 character set. This means it is the same as the official ISO 8859-1 or IANA (Internet Assigned Numbers Authority) latin1, except that IANA latin1 treats the code points between 0x80 and 0x9f as “undefined,” whereas cp1252, and therefore MySQL's latin1, assign characters for those positions. For example, 0x80 is the Euro sign. For the “undefined” entries in cp1252, MySQL translates 0x81 to Unicode 0x0081, 0x8d to 0x008d, 0x8f to 0x008f, 0x90 to 0x0090, and 0x9d to 0x009d.

这样在Java中，如果使用标准的iso-8859-1或者cp1252解码可能出现乱码。
s.getBytes("iso-8859-1") 或者 s.getBytes("cp1252");

写了一段代码来解决这个问题
private String convertCharset(String s){
        if(s!=null){
            try {
                int length = s.length();
                byte[] buffer = new byte[length];
                //0x81 to Unicode 0x0081, 0x8d to 0x008d, 0x8f to 0x008f, 0x90 to 0x0090, and 0x9d to 0x009d.
                for(int i=0;i<length;++i){
                    char c = s.charAt(i);
                    if(c==0x0081){
                        buffer[i]=(byte)0x81;
                    }
                    else if(c==0x008d){
                        buffer[i]=(byte)0x8d;
                    }
                    else if(c==0x008f){
                        buffer[i]=(byte)0x8f;