JDBC链接mysql插入数据后显示问号的原因及解决办法

1.在cmd中进入mysql查看默认的编码格式:

mysql> show variables like "%char%";

若不是utf8(因为我用的是utf8)，关掉mysql服务，在my.ini中添加

[client]
default-character-set=utf8
[mysqld]
default-storage-engine=INNODB
character-set-server=utf8
collation-server=utf8_general_ci
[mysql]
default-character-set=utf8

2.eclipse中的编码格式是否为utf8

3.如果还是不可以，检查mysql客户端表格的编码方式

show create table tablename 

如果不是utf-8.删掉重新建立一张表（之前我在原表上改动没有成功，可能是我自己操作的原因）

分享一个经典的JDBC连接MySQL的程序

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class MySQLConnection {
public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
String url = null;
String user = null;
String password = null;
String sql = null;
try {
Class.forName("com.mysql.jdbc.Driver"); //加载mysq驱动
} catch (ClassNotFoundException e) {
System.out.println("驱动加载错误");
e.printStackTrace();//打印出错详细信息
}
try {
url = 
"jdbc:mysql://localhost/test?user=root&password=yqs2602555&useUnicode=true&&characterEncoding=gb2312&autoReconnect = true";//简单写法：url = "jdbc:myqsl://localhost/test(数据库名)? user=root(用户)&password=yqs2602555(密码)";
user = "root";
password = "yqs2602555";
conn = DriverManager.getConnection(url,user,password);
} catch (SQLException e) {
System.out.println("数据库链接错误");
e.printStackTrace();
}
try {
stmt = conn.createStatement();
sql = "select * from dept";//dept这张表有deptno，deptname和age这三个字段
rs = stmt.executeQuery(sql);//执行sql语句
while(rs.next()) {
System.out.print(rs.getInt("deptno") + " ");
System.out.print(rs.getString("deptname") + " ");
System.out.println(rs.getInt("age") + " ");
}
} catch (SQLException e) {
System.out.println("数据操作错误");
e.printStackTrace();
}
//关闭数据库
try {
if(rs != null) {
rs.close();
rs = null;
}
if(stmt != null) {
stmt.close();
stmt = null;
}
if(conn != null) {
conn.close();
conn = null;
}
} catch(Exception e) {
System.out.println("数据库关闭错误");
e.printStackTrace();
}
}
}

运行结果如下：

1 yqs 0
2 hello 0
3 yqsshr 0
4 world 0
5 hryspa 0
1 yqs 0
2 hello 0
3 yqsshr 0
4 world 0
5 hryspa 0
1 yqs11 21
1 yqs21 31
1 yqs31 41
1 yqs41 51