运行 Java 代码时出错(未知字符集：'utf8mb4')？

Question

我正在尝试学习Java编程以及如何将其与数据库MySQL链接。。。

这是代码：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

public class main {
    public static void main(String[] args) 
    throws Exception 
    {
        System.out.println("Loading Driver ..");
        System.out.println("Loading Driver ...");
        System.out.println("Loading Driver ....");
        System.out.println("Loading Driver .....");
        Class.forName("com.mysql.jdbc.Driver");
        System.out.println("Driver Loaded");
        Connection con = DriverManager.getConnection("jdbc:mysql://localhost/javabook", "root", "1234"); //Connect
        System.out.println("Database Connected");
        PreparedStatement statement = con.prepareStatement(" SELECT * From acc_types");
        ResultSet result = statement.executeQuery();
        while (result.next())
        {
            System.out.println(result.getString(1)+ ""+result.getString(2));
        }


}
}

说：

Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown character set: 'utf8mb4'
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
    at com.mysql.jdbc.Util.getInstance(Util.java:386)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1052)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3609)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3541)
    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2002)
    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2163)
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2618)
    at com.mysql.jdbc.ConnectionImpl.configureClientCharacterSet(ConnectionImpl.java:1880)
    at com.mysql.jdbc.ConnectionImpl.initializePropsFromServer(ConnectionImpl.java:3499)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2384)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2153)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:792)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:381)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at main.main(main.java:22)

嗯，我一直在谷歌和YouTube上搜索，但没有回答这样的问题。。。我已经按照这个教程一步一步地安装好了程序。。。（http://www.youtube.com/watch?v=E30_-pQQXs）

我真的需要帮助。。。。

Answer 1

utf8mb4字符集是MySQL特有的。这里有解释。异常是因为JDBC驱动程序无法识别该字符集。一种解决方案是将数据库编码转换为utf8。另一个是使用不同的JDBC驱动程序。（MySQL连接器/J 5.1.13及以上版本支持utf8mb4。）

Answer 2

检查数据库并确保整个数据库+表+字段具有相同的字符集。这是一个真实的表示例，您可以看到字符集是为表的字段AND设置的。当然，数据库也是用字符集创建的。

CREATE TABLE `politicas` (
  `ID` int(11) NOT NULL AUTO_INCREMENT,
  `Nombre` varchar(250) CHARACTER SET utf8mb4 NOT NULL,
  `Texto` text CHARACTER SET utf8mb4 NOT NULL,
  `Lng` varchar(2) CHARACTER SET utf8mb4 NOT NULL,
  PRIMARY KEY (`ID`)
) ENGINE=MyISAM AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;