Question

为什么jdbc连接不上数据库，求指导

package jdbc;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
public class AAA {
private static String driverClassName;
private static String url;
private static String username;
private static String password;
public static void getParam(String filename){
Properties propes=new Properties();
File file=new File(filename);
try {
FileInputStream fis=new FileInputStream(file);
propes.load(fis);
driverClassName=propes.getProperty("driverClassName");
url=propes.getProperty("url");
username=propes.getProperty("username");
password=propes.getProperty("password");
System.out.println(driverClassName);
System.out.println(url);
System.out.println(username);
System.out.println(password);
} catch (FileNotFoundException e) {
e.printStackTrace();
}catch(IOException e){
e.printStackTrace();
}
}
public static void getEmpData(){
Connection conn=null;
Statement stmt=null;
ResultSet rs=null;
String sql="select * from emp";
try {
Class.forName(driverClassName);
conn=DriverManager.getConnection(url,username,password);
stmt=conn.createStatement();
rs=stmt.executeQuery(sql);
while(rs.next()){
int id=rs.getInt("id");
String name=rs.getString("name");
int age=rs.getInt("age");
System.out.println(id+","+name+","+age);
}
rs.close();
conn.close();
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static void main(String[] args) {
getParam("src/db_mysql.properties");
getEmpData();
}
}
}
错误提示

Answer 1

你的sql jdbc驱动类没有加载成功，

你可以试试这样:

1. 如果是web目录，将驱动.jar文件放入tomcat的lib目录中

2. 应用程序可以将存放驱动.jar的文件夹放入classpath环境变量中。

追问

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