Question

Exception in thread "main" java.lang.NullPointerException at 连接数据库.Con

public class ConnectToJdbc {
public static void main(String[] args) {
Connection con = null;
java.sql.Statement sql;
ResultSet rs;
try {
Class.forName("com.mysql.jdbc.Driver");//加载JDBC驱动
} catch (Exception e) {
// TODO: handle exception
}
String uri = "jdbc:mysql://localhost:3306/students?useSSL=true";
String user = "root";
String password = "123456";
try {
con = DriverManager.getConnection(uri,user,password);
} catch (SQLException e) {
// TODO: handle exception
}
try {
sql = con.createStatement();
rs = sql.executeQuery("SELECT * FROM student");
while(rs.next()){
String num = rs.getString(1);
String name = rs.getString(2);
String sex = rs.getString(3);
int age = rs.getInt(4);
Reader zhuangye = rs.getCharacterStream(5);
System.out.printf("%s\t",num);
System.out.printf("%s\t",name);
System.out.printf("%s\t",sex);
System.out.printf("%s\t",age);
System.out.printf("%s\t",zhuangye);
}
con.close();
} catch (SQLException e) {
// TODO: handle exception
}
}
}

Answer 1

Class.forName("com.mysql.jdbc.Driver").newInstance();//加载JDBC驱动

追问

这里有什么问题吗

追答

加上   .newInstance()

另外

try {
con = DriverManager.getConnection(uri,user,password);
} catch (Exception e) {
     e.printStackTrace();
}

改成这样.把异常打出来,不要把异常吃掉.你这里肯定是没取到数据库连接,然后你又把异常吃掉了

追问

我试一下，谢谢了，还是报了同样的错误

追答

按我的那样改一下.如果有什么问题.会把异常信息打印出来.下次追问,记得把异常信息带上来.

追问

恩，
java.sql.SQLException: No suitable driver found for jdbc:mysql://localhost:3306/students?useSSL=true
at java.sql.DriverManager.getConnection(DriverManager.java:689)
at java.sql.DriverManager.getConnection(DriverManager.java:247)
at 连接数据库.ConnectToJdbc.main(ConnectToJdbc.java:23)

追答

没有加载到驱动的jar包.你确定你的mysql的驱动放在classpath下面了么?你的jar包名叫什么?
而且你为什么要useSSL?把那一段去掉.mysql://localhost:3306/students就好了.
或者jdbc:mysql://localhost:3306/students?useUnicode=true&characterEncoding=utf8&allowMultiQueries=true