emoji表情插入資料庫異常記錄
utf-8編碼可能2個位元組、3個位元組、4個位元組的字元，但是MySQL的utf8編碼只支援3位元組的資料，而移動端的表情資料是4個位元組的字元。如果直接往採用utf-8編碼的資料庫中插入表情資料，Java程式中將報SQL異常：
java.sql.SQLException: Incorrect string value: ‘\xF0\x9F\x92\x94’ for column ‘name’ at row 1 at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1073) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3593) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3525) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1986) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2140) at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2620) at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1662) at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1581)
可以對4位元組的字元進行編碼儲存，然後取出來的時候，再進行解碼。但是這樣做會使得任何使用該字元的地方都要進行編碼與解碼。
utf8mb4編碼是utf8編碼的超集，相容utf8，並且能儲存4位元組的表情字元。 採用utf8mb4編碼的好處是：儲存與獲取資料的時候，不用再考慮表情字元的編碼與解碼問題。
更改資料庫的編碼為utf8mb4:
1. MySQL的版本
utf8mb4的最低mysql版本支援版本為5.5.3+，若不是，請升級到較新版本。
2. MySQL驅動
5.1.34可用,最低不能低於5.1.13
3.修改MySQL配置檔案
修改mysql配置檔案my.cnf（windows為my.ini） my.cnf一般在etc/mysql/my.cnf位置。找到後請在以下三部分裡新增如下內容： [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'
4. 重啟資料庫，檢查變數
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 |
collation_connection 、collation_database 、collation_server是什麼沒關係。
但必須保證
| 系統變數 | 描述 |
|---|---|
| character_set_client | (客戶端來源資料使用的字符集) |
| character_set_connection | (連線層字符集) |
| character_set_database | (當前選中資料庫的預設字符集) |
| character_set_results | (查詢結果字符集) |
| character_set_server | (預設的內部操作字符集) |
這幾個變數必須是utf8mb4。
5. 資料庫連線的配置
資料庫連線引數中: characterEncoding=utf8會被自動識別為utf8mb4，也可以不加這個引數，會自動檢測。 而autoReconnect=true是必須加上的。
6. 將資料庫和已經建好的表也轉換成utf8mb4
更改資料庫編碼：ALTER DATABASE caitu99 CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;
更改表編碼：ALTER TABLE TABLE_NAME CONVERT TO CHARACTER SET utf8mb4 COLLATEutf8mb4_general_ci;
如有必要，還可以更改列的編碼
7、在第3步設定character_set_database，character_set_server不成功的可以試下直接在mysql.exe下
set @@character_set_server='utf8mb4';
set @@character_set_database='utf8mb4';
這下資料庫就可以存下emoji表情的編碼了。
附上我的my.ini
# For advice on how to change settings please see
# http://dev.mysql.com/doc/refman/5.6/en/server-configuration-defaults.html
# *** DO NOT EDIT THIS FILE. It's a template which will be copied to the
# *** default location during install, and will be replaced if you
# *** upgrade to a newer version of MySQL.
[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'
# Remove leading # and set to the amount of RAM for the most important data
# cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%.
# innodb_buffer_pool_size = 128M
# Remove leading # to turn on a very important data integrity option: logging
# changes to the binary log between backups.
# log_bin
# These are commonly set, remove the # and set as required.
# basedir = .....
# datadir = .....
# port = .....
# server_id = .....
# Remove leading # to set options mainly useful for reporting servers.
# The server defaults are faster for transactions and fast SELECTs.
# Adjust sizes as needed, experiment to find the optimal values.
# join_buffer_size = 128M
# sort_buffer_size = 2M
# read_rnd_buffer_size = 2M
sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES