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