更改MySQL数据库的编码为utf8mb4问题
作者:woslx
utf-8编码可能1个字节、2个字节、3个字节、4个字节的字符,但是MySQL的utf8编码只支持最多3字节的数据,也就是说mysql最开始的时候,对utf-8的支持是不完整的。而emoji表情字符是4个字节的字符。
如果直接往采用utf-8编码的数据库中插入表情数据
java程序中将报SQL异常:
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)
可以对4字节的字符进行编码存储,然后取出来的时候,再进行解码。但是这样做会使得任何使用该字符的地方都要进行编码与解码。
为了支持完整的utf-8编码,mysql推出了utf8mb4,它是mysql平台上utf8编码的超集,兼容utf8,并且能存储4字节的表情字符。
采用utf8mb4编码的好处是:存储与获取数据的时候,不用再考虑表情字符的编码与解码问题。
更改数据库的编码为utf8mb4:
1. MySQL的版本
utf8mb4的最低mysql版本支持版本为5.5.3+,若不是,请升级到较新版本。
2. MySQL驱动
5.1.34可用,最低不能低于5.1.13
3. 修改MySQL配置文件
修改mysql配置文件my.cnf(windows为my.ini)
my.cnf一般在/etc/mysql/my.cnf位置。找到后请在以下三部分里添加如下内容:
[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. 重启数据库,检查变量
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是什么没关系。
但必须保证下面几个变量必须是utf8mb4。
系统变量 | 描述 |
---|---|
character_set_client | (客户端来源数据使用的字符集) |
character_set_connection | (连接层字符集) |
character_set_database | (当前选中数据库的默认字符集) |
character_set_results | (查询结果字符集) |
character_set_server | (默认的内部操作字符集) |
5. 数据库连接的配置
数据库连接参数中:
characterEncoding=utf8会被自动识别为utf8mb4,也可以不加这个参数,会自动检测。
而autoReconnect=true是必须加上的。
6. 将数据库和已经建好的表也转换成utf8mb4
更改数据库编码:
ALTER DATABASE caitu99 CHARACTER SET `utf8mb4` COLLATE `utf8mb4_general_ci`;
更改表编码:
ALTER TABLE `TABLE_NAME` CONVERT TO CHARACTER SET `utf8mb4` COLLATE `utf8mb4_general_ci`;
如有必要,还可以更改列的编码
可以写代码批量进行转换:
//获取所有表 Connection conn = null; try { conn = DbUtilsTool.openConn("MySQL", "127.0.0.1", "3306", "caitu99", "root", "root"); String sql = "show tables"; QueryRunner qr = new QueryRunner(); List<String> tblNameList= (List<String>) qr.query(conn, sql, new ColumnListHandler(1)); sql = "ALTER DATABASE caitu99 CHARACTER SET `utf8mb4` COLLATE `utf8mb4_general_ci`"; qr.update(conn,sql); for (String str:tblNameList) { sql = "ALTER TABLE "+str+" CONVERT TO CHARACTER SET `utf8mb4` COLLATE `utf8mb4_general_ci`"; qr.update(conn,sql); } } catch (Exception e) { e.printStackTrace(); throw new RuntimeException(e); } finally { if(conn!=null) { try { conn.close(); } catch (SQLException e) { e.printStackTrace(); } } }
DbUtilsTool类:
package com.mysql.chartest; import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import java.util.List; import java.util.Map; import org.apache.commons.dbutils.BasicRowProcessor; import org.apache.commons.dbutils.BeanProcessor; import org.apache.commons.dbutils.QueryRunner; import org.apache.commons.dbutils.handlers.ArrayHandler; import org.apache.commons.dbutils.handlers.ArrayListHandler; import org.apache.commons.dbutils.handlers.BeanHandler; import org.apache.commons.dbutils.handlers.BeanListHandler; import org.apache.commons.dbutils.handlers.ColumnListHandler; import org.apache.commons.dbutils.handlers.KeyedHandler; import org.apache.commons.dbutils.handlers.MapHandler; import org.apache.commons.dbutils.handlers.MapListHandler; import org.apache.commons.dbutils.handlers.ScalarHandler; public class DbUtilsTool { private static final QueryRunner runner = new QueryRunner(); /* 打开数据库连接(type: MySQL,Oracle,SQLServer) */ public static Connection openConn(String type, //数据库类型 String host, //主机ip String port, //主机端口 String name, //数据库名 String username, //用户名 String password)//密码 { Connection conn = null; try { String driver; String url; if (type.equalsIgnoreCase("MySQL")) { driver = "com.mysql.jdbc.Driver"; url = "jdbc:mysql://" + host + ":" + port + "/" + name; } else if (type.equalsIgnoreCase("Oracle")) { driver = "oracle.jdbc.driver.OracleDriver"; url = "jdbc:oracle:thin:@" + host + ":" + port + ":" + name; } else if (type.equalsIgnoreCase("SQLServer")) { driver = "com.microsoft.jdbc.sqlserver.SQLServerDriver"; url = "jdbc:sqlserver://" + host + ":" + port + ";databaseName=" + name; } else { throw new RuntimeException(); } Class.forName(driver); conn = DriverManager.getConnection(url, username, password); } catch (Exception e) { e.printStackTrace(); } return conn; } /* 关闭数据库连接 */ public static void closeConn(Connection conn) { try { if (conn != null) { conn.close(); } } catch (Exception e) { e.printStackTrace(); } } /* 查询(返回Array结果) */ public static Object[] queryArray(Connection conn, String sql, Object... params) { Object[] result = null; try { result = runner.query(conn, sql, new ArrayHandler(), params); } catch (SQLException e) { e.printStackTrace(); } return result; } /* 查询(返回ArrayList结果) */ public static List<Object[]> queryArrayList(Connection conn, String sql, Object... params) { List<Object[]> result = null; try { result = runner.query(conn, sql, new ArrayListHandler(), params); } catch (SQLException e) { e.printStackTrace(); } return result; } /* 查询(返回Map结果) */ public static Map<String, Object> queryMap(Connection conn, String sql, Object... params) { Map<String, Object> result = null; try { result = runner.query(conn, sql, new MapHandler(), params); } catch (SQLException e) { e.printStackTrace(); } return result; } /* 查询(返回MapList结果) */ public static List<Map<String, Object>> queryMapList(Connection conn, String sql, Object... params) { List<Map<String, Object>> result = null; try { result = runner.query(conn, sql, new MapListHandler(), params); } catch (SQLException e) { e.printStackTrace(); } return result; } /* 查询(返回Bean结果) */ public static <T> T queryBean(Class<T> cls, Map<String, String> map, Connection conn, String sql, Object... params) { T result = null; try { if (map != null) { result = runner.query(conn, sql, new BeanHandler<T>(cls, new BasicRowProcessor(new BeanProcessor(map))), params); } else { result = runner.query(conn, sql, new BeanHandler<T>(cls), params); } } catch (SQLException e) { e.printStackTrace(); } return result; } /* 查询(返回BeanList结果) */ public static <T> List<T> queryBeanList(Class<T> cls, Map<String, String> map, Connection conn, String sql, Object... params) { List<T> result = null; try { if (map != null) { result = runner.query(conn, sql, new BeanListHandler<T>(cls, new BasicRowProcessor(new BeanProcessor(map))), params); } else { result = runner.query(conn, sql, new BeanListHandler<T>(cls), params); } } catch (SQLException e) { e.printStackTrace(); } return result; } /* 查询指定列名的值(单条数据) */ public static <T> T queryColumn(String column, Connection conn, String sql, Object... params) { T result = null; try { result = runner.query(conn, sql, new ScalarHandler<T>(column), params); } catch (SQLException e) { e.printStackTrace(); } return result; } /* 查询指定列名的值(多条数据) */ public static <T> List<T> queryColumnList(String column, Connection conn, String sql, Object... params) { List<T> result = null; try { result = runner.query(conn, sql, new ColumnListHandler<T>(column), params); } catch (SQLException e) { e.printStackTrace(); } return result; } /* 查询指定列名对应的记录映射 */ public static <T> Map<T, Map<String, Object>> queryKeyMap(String column, Connection conn, String sql, Object... params) { Map<T, Map<String, Object>> result = null; try { result = runner.query(conn, sql, new KeyedHandler<T>(column), params); } catch (SQLException e) { e.printStackTrace(); } return result; } /* 更新(包括UPDATE、INSERT、DELETE,返回受影响的行数) */ public static int update(Connection conn, String sql, Object... params) { int result = 0; try { result = runner.update(conn, sql, params); } catch (SQLException e) { e.printStackTrace(); } return result; } }
以上为个人经验,希望能给大家一个参考,也希望大家多多支持脚本之家。