java.sql.SQLException: Unknown initial character set index '255' received from server. Initial client character set can be forced via the 'characterEncoding' property.

1.报错信息

java.sql.SQLException: Unknown initial character set index '255' received from server. Initial client character set can be forced via the 'characterEncoding' property.
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1055)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:926)
    at com.mysql.jdbc.ConnectionImpl.configureClientCharacterSet(ConnectionImpl.java:1672)
    at com.mysql.jdbc.ConnectionImpl.initializePropsFromServer(ConnectionImpl.java:3425)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2045)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:718)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:302)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:282)
    at java.sql.DriverManager.getConnection(DriverManager.java:664)
    at java.sql.DriverManager.getConnection(DriverManager.java:247)
    at com.yg.test.JDBCTest.main(JDBCTest.java:17)

2.原因

　　这个错误是在使用JDBC连接mysql数据库时没有设置字符集

　　起因就是在设置JDBC的url时使用的是"jdbc:mysql://localhost:3306/数据库名称"的方式

3.解决方式

　　将url信息从"jdbc:mysql://localhost:3306/数据库名称"改为"jdbc:mysql://localhost:3306/数据库名称?useUnicode=true&characterEncoding=字符集名称"

　　注意:

　　　　数据库名称为自己项目要连接的数据库名称;

　　　　字符集名称为项目连接的数据库使用的编码字符集名称;