Is it a bug in MySQL or in java-connector？

Description

         In mysql-connector-java-5.1.27, the charset utf8mb4 is supported. But the steps and result bellow looks buggy.

1、  set character_set_server=gbk in my.cnf

2、  start mysql

3、  execute  set global character_set_server=utfmb4;

4、  insert a data with utf8mb4 characters

Result: error data inserted.

 

Analysis

         Direct reason: Java connector believes that the server use gbk as the default set, so deal the data with the rule of gbk;

         Deeper reason:

1\ set global character_set_server=utfmb4 just change the global_system_variables, but not the default_charset_info and default_character_set_name.

2\ when handshake, MySQL server writes server characteristics to client, using default_charset_info->number, 28, which is the CharsetIndex of gbk.

 

Compare

         As comparison, the steps change to

1、  set character_set_server= utfmb4 in my.cnf

2、  insert a data with utf8mb4 characters

Result: correct data inserted.

         Because the default charset is utfmb4 now, the connector treats dada correctly.

Discussion

         There are two ways to resolve this problem.

         1\ MySQL sends the current character info number in global_system_variables when handshake

         2\ Java connector get the correct character to use by “select @@character_set_server;”

 

So , is it a bug for MySQL or java-connector?

 

评论

1 楼 houyujiangjun 2013-11-19  

yup, it is  a bug for the lower version of MySQL.
update to version 5.5 or later, you will find your  solution.