jdbc 数据库的连接 以及数据库的增删改查

Posted 2020-10-02 骑着猪猛跑

package util;

import java.sql.Connection;
import java.sql.DriverManager;

public class Jdbcutil {
private static Connection conn=null;
static{
String url="jdbc:mysql://localhost:3306/test";
String username="root";
String password="1234";
String driverClass="com.mysql.jdbc.Driver";


try {Class.forName(driverClass);//
conn = DriverManager.getConnection(url, username, password); //
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static Connection getConnection(){

if(conn!=null){
return conn;
}
else {
return null;
}

}

}

 

查询

public List<Student> getStudentList(){

PreparedStatement preparedStatement=null;
ResultSet rs=null;
List<Student> studentlist=new ArrayList<Student>();
Connection connection=Jdbcutil.getConnection();
String sql="select * from student";
try {
preparedStatement=connection.prepareStatement(sql);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
rs = preparedStatement.executeQuery();
while (rs.next()) {
Student student=new Student();
int id=rs.getInt("id");
String name=rs.getString("name");
String school=rs.getString("school");
double score=rs.getDouble("score");
student.setId(id);
student.setName(name);
student.setSchool(school);
student.setScore(score);
studentlist.add(student);

}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}


return studentlist;}

 

增删改

public void tianjia(String userid,String username,String userschool,String userscore){
PreparedStatement preparedStatement=null;
Connection connection=Jdbcutil.getConnection();
String sql="insert into student values (?,?,?,?)";
try {
preparedStatement=connection.prepareStatement(sql);
preparedStatement.setObject(1, userid);
preparedStatement.setObject(2, username);
preparedStatement.setObject(3, userschool);
preparedStatement.setObject(4, userscore);
preparedStatement.executeUpdate();

} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}

 

public void shanchu(String userid){
PreparedStatement preparedStatement=null;
Connection connection=Jdbcutil.getConnection();
String sql="DELETE FROM student WHERE id=‘"+userid+"‘";
try {
preparedStatement=connection.prepareStatement(sql);
preparedStatement.executeUpdate();

} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}

 

public void xiugai(String userid,String username,String userschool,String userscore){
PreparedStatement preparedStatement=null;
Connection connection=Jdbcutil.getConnection();
String sql="update student set id=?,name=?,school=?,score=? where id=‘"+userid+"‘";
try {
preparedStatement=connection.prepareStatement(sql);
preparedStatement.setObject(1, userid);
preparedStatement.setObject(2, username);
preparedStatement.setObject(3, userschool);
preparedStatement.setObject(4, userscore);
preparedStatement.executeUpdate();

} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}