MySQL utf8与utf8mb4

2017-03-13  本文已影响1274人  Cursor_fei

报错信息:

java.lang.RuntimeException: java.sql.SQLException: 
Incorrect string value: '\\xF0\\x9F\\x9A\\xB9\\xE4\\xBC...' for column 'xxx' ...

引起的原因:
在varchar类型的字段里面插入的text包含emoj表情。
MySQL 5.5.3 版本以下,CHARACTER SET 为 utf8 的字段最长只有3个字节。
查看MySQL版本可用以下命令:

mysql> status;
--------------
mysql  Ver 14.14 Distrib 5.7.17, for Linux (x86_64) using  EditLine wrapper

Connection id:      5
Current database:   
Current user:       root@localhost
SSL:            Not in use
Current pager:      stdout
Using outfile:      ''
Using delimiter:    ;
Server version:     5.7.17-0ubuntu0.16.04.1 (Ubuntu)
Protocol version:   10
Connection:     Localhost via UNIX socket
Server characterset:    utf8mb4
Db     characterset:    utf8mb4
Client characterset:    utf8mb4
Conn.  characterset:    utf8mb4
UNIX socket:        /var/run/mysqld/mysqld.sock
Uptime:         1 hour 28 min 58 sec

Threads: 1  Questions: 28  Slow queries: 0  Opens: 116  Flush tables: 1  Open tables: 29  Queries per second avg: 0.005
--------------

查看相关字符集设置信息(下面是我修改后的,修改前utf8mb4处都为utf8):

mysql>  show variables like 'character_set_%';
+--------------------------+----------------------------+
| Variable_name            | Value                      |
+--------------------------+----------------------------+
| character_set_client     | utf8mb4                    |
| character_set_connection | utf8mb4                    |
| character_set_database   | utf8mb4                    |
| character_set_filesystem | binary                     |
| character_set_results    | utf8mb4                    |
| character_set_server     | utf8mb4                    |
| character_set_system     | utf8                       |
| character_sets_dir       | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+

查看所有字符集信息:

mysql> show character set;
+----------+---------------------------------+---------------------+--------+
| Charset  | Description                     | Default collation   | Maxlen |
+----------+---------------------------------+---------------------+--------+
| big5     | Big5 Traditional Chinese        | big5_chinese_ci     |      2 |
| dec8     | DEC West European               | dec8_swedish_ci     |      1 |
| cp850    | DOS West European               | cp850_general_ci    |      1 |
| hp8      | HP West European                | hp8_english_ci      |      1 |
| koi8r    | KOI8-R Relcom Russian           | koi8r_general_ci    |      1 |
| latin1   | cp1252 West European            | latin1_swedish_ci   |      1 |
| latin2   | ISO 8859-2 Central European     | latin2_general_ci   |      1 |
| swe7     | 7bit Swedish                    | swe7_swedish_ci     |      1 |
| ascii    | US ASCII                        | ascii_general_ci    |      1 |
| ujis     | EUC-JP Japanese                 | ujis_japanese_ci    |      3 |
| sjis     | Shift-JIS Japanese              | sjis_japanese_ci    |      2 |
| hebrew   | ISO 8859-8 Hebrew               | hebrew_general_ci   |      1 |
| tis620   | TIS620 Thai                     | tis620_thai_ci      |      1 |
| euckr    | EUC-KR Korean                   | euckr_korean_ci     |      2 |
| koi8u    | KOI8-U Ukrainian                | koi8u_general_ci    |      1 |
| gb2312   | GB2312 Simplified Chinese       | gb2312_chinese_ci   |      2 |
| greek    | ISO 8859-7 Greek                | greek_general_ci    |      1 |
| cp1250   | Windows Central European        | cp1250_general_ci   |      1 |
| gbk      | GBK Simplified Chinese          | gbk_chinese_ci      |      2 |
| latin5   | ISO 8859-9 Turkish              | latin5_turkish_ci   |      1 |
| armscii8 | ARMSCII-8 Armenian              | armscii8_general_ci |      1 |
| utf8     | UTF-8 Unicode                   | utf8_general_ci     |      3 |
| ucs2     | UCS-2 Unicode                   | ucs2_general_ci     |      2 |
| cp866    | DOS Russian                     | cp866_general_ci    |      1 |
| keybcs2  | DOS Kamenicky Czech-Slovak      | keybcs2_general_ci  |      1 |
| macce    | Mac Central European            | macce_general_ci    |      1 |
| macroman | Mac West European               | macroman_general_ci |      1 |
| cp852    | DOS Central European            | cp852_general_ci    |      1 |
| latin7   | ISO 8859-13 Baltic              | latin7_general_ci   |      1 |
| utf8mb4  | UTF-8 Unicode                   | utf8mb4_general_ci  |      4 |
| cp1251   | Windows Cyrillic                | cp1251_general_ci   |      1 |
| utf16    | UTF-16 Unicode                  | utf16_general_ci    |      4 |
| utf16le  | UTF-16LE Unicode                | utf16le_general_ci  |      4 |
| cp1256   | Windows Arabic                  | cp1256_general_ci   |      1 |
| cp1257   | Windows Baltic                  | cp1257_general_ci   |      1 |
| utf32    | UTF-32 Unicode                  | utf32_general_ci    |      4 |
| binary   | Binary pseudo charset           | binary              |      1 |
| geostd8  | GEOSTD8 Georgian                | geostd8_general_ci  |      1 |
| cp932    | SJIS for Windows Japanese       | cp932_japanese_ci   |      2 |
| eucjpms  | UJIS for Windows Japanese       | eucjpms_japanese_ci |      3 |
| gb18030  | China National Standard GB18030 | gb18030_chinese_ci  |      4 |
+----------+---------------------------------+---------------------+--------+

由上表可见,utf8最长3个字节。

在5.5.3版本以后,增加了 [utf8mb4] (https://dev.mysql.com/doc/refman/5.5/en/charset-unicode-utf8mb4.html) 字符集。
这是官方原文:

The character set named utf8 uses a maximum of three bytes per character and contains only BMP characters. As of MySQL 5.5.3, the utf8mb4 character set uses a maximum of four bytes per character supports supplementary characters:

因此,只需要将字符集由utf8修改为utf8mb4即可支持4字节的BPM等数据。

如何修改:
修改MySQL配置文件,修改mysql的客户端默认连接字符集,服务端以及数据库的默认字符集:

sudo vim /etc/mysql/my.cnf

在末尾或者已有的中括号里的块中加上如下配置:

[client]
default-character-set = utf8mb4

[mysql]
default-character-set = utf8mb4

[mysqld]
character-set-client-handshake = FALSE
character-set-server = utf8mb4
collation-server = utf8mb4_unicode_ci
init_connect='SET NAMES utf8mb4'

重启MySQL服务:

sudo service mysql restart

重启服务后,通过以下SQL可以查看结果:

mysql> SHOW VARIABLES WHERE Variable_name LIKE 'character\_set\_%' OR Variable_name LIKE 'collation%';
+--------------------------+--------------------+
| Variable_name            | Value              |
+--------------------------+--------------------+
| character_set_client     | utf8mb4            |
| character_set_connection | utf8mb4            |
| character_set_database   | utf8mb4            |
| character_set_filesystem | binary             |
| character_set_results    | utf8mb4            |
| character_set_server     | utf8mb4            |
| character_set_system     | utf8               |
| collation_connection     | utf8mb4_unicode_ci |
| collation_database       | utf8mb4_unicode_ci |
| collation_server         | utf8mb4_unicode_ci |
+--------------------------+--------------------+

MySQL方面修改好后,需要修改已有的数据库或者表或者字段:
修改表的字符集:

ALTER TABLE tablename charset=utf8mb4;

修改表字段:

ALTER TABLE tablename MODIFY COLUMN columnname VARCHAR(255) CHARACTER SET utf8mb4;

修改表的字符集和修改字段可以用一条SQL完成。

如果使用的java连接MySQL,需要修改原有的连接设置:
原jdbcUrl:jdbc:mysql:///dbname?useUnicode=true&characterEncoding=UTF-8
需要去掉编码参数:
jdbcUrl:jdbc:mysql:///dbname

** 此处不要想当然的将参数useUnicode=true&characterEncoding=UTF-8修改为useUnicode=true&characterEncoding=utf8mb4
,否则会报出以下错误:

Could not get JDBC Connection; nested exception is com.MySQL.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: 
Unknown character set: 'utf8mb4'

我们在MySQL的配置文件里已经配置了[client]的默认访问字符集了,所以,此处将参数去掉即可。

吃水不忘打井人:
http://blog.csdn.net/secretx/article/details/21253559
http://stackoverflow.com/questions/7814293/how-to-insert-utf-8-mb4-characteremoji-in-ios5-in-mysql

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