Servlet connection to database

Question

I am trying to connect to jdbc database from servlet.I have separate class dbconnect for connection and inserting data to database.

Here is my dbconnect class:

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

public class dbconnect {
    Connection conn;
    Statement stm;

    dbconnect(){
      try{
        Class.forName("org.apache.derby.jdbc.ClientDriver");  
        conn = DriverManager.getConnection
         ("jdbc:derby://localhost:1527/type","nika",
         "mypass");  
        stm = conn.createStatement();
        System.out.println("success");
        String sql = "INSERT INTO USERS " + "VALUES (\"[email protected]\", \"nika\", \"nika\", \"kaci\")";
        stm.executeUpdate(sql);
      }  
      catch (Exception ex){
          System.out.println(ex.getMessage());
      }
    }
}

In servlet I create new dbconnect object which must insert data to database,but it does not happen.

Can anyone tell me why it does not work? I guess I make fundamental mistake.

Thank you.

For more details I have jsp file which sends html form data to this servlet and then I try to write these data to database using dbconnect class.

I have changed dbconnect class like this,now I use preparedstatement to write files but still does not work.

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.Statement;

public class dbconnect {
    Connection conn;
    Statement stm;

    dbconnect(){
      try{
        Class.forName("org.apache.derby.jdbc.ClientDriver");  
        conn = DriverManager.getConnection("jdbc:derby://localhost:1527/type","nika","nika");  
        stm = conn.createStatement();
        System.out.println("success");
        String sql = "INSERT INTO NIKA.USERS (mail, pass, gender, saxeli) VALUES (?, ?, ?, ?)";
        PreparedStatement statement = conn.prepareStatement(sql);
        statement.setString(1, "tsogiaidze");
        statement.setString(2, "nika");
        statement.setString(2, "nika");
        statement.setString(2, "kaci");
        int rowsInserted = statement.executeUpdate();
        if (rowsInserted > 0) {
        System.out.println("A new user was inserted successfully!");
        }
      }  
      catch (Exception ex){
          System.out.println(ex.getMessage());
      }
    }

}

As noted, check any exceptions, otherwise first check that you can manually execute the INSERT statment and if that works then attach a debugging session and step through. — Robert
– Robert, Commented Jun 23, 2014 at 18:06
If you mind about security that I am not closing connections and so on I do not care about it yet.Can you tell me exactly what is bad practice in my code?Servlet works itself,but does not add any values to the database. — Nika Tsogiaidze
– Nika Tsogiaidze, Commented Jun 23, 2014 at 18:06
That is strange you don't get an exception. Maybe confirm this by writing more to stdout (ex.getMessage can be empty, relying on the message alone is not a good idea), also see what the return value of executeUpdate is. — Nathan Hughes
– Nathan Hughes, Commented Jun 23, 2014 at 19:01

user327961 · Accepted Answer · 2014-06-23 19:40:24Z

2

Use single quote to surround your texts.

String sql = "INSERT INTO USERS VALUES ("
    + "'[email protected]', 'nika', 'nika', 'kaci')";

Or better, use a PreparedStatement:

    String sql = "INSERT INTO USERS VALUES (?, ?, ?, ?)");
    PreparedStatement stm = conn.prepareStatement(sql);
    System.out.println("success");
    stm.setString(1, "[email protected]");
    stm.setString(2, "nika");
    stm.setString(3, "nika");
    stm.setString(4, "kaci");
    stm.executeUpdate();

edited Jun 23, 2014 at 19:40

answered Jun 23, 2014 at 18:20

user327961

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Comments

SparkOn · Accepted Answer · 2014-06-23 18:25:08Z

1

Your insert statement is possibly wrong try this

       try{
            Class.forName("com.mysql.jdbc.Driver");
            System.out.println("making connection");
            Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "welcome");
            PreparedStatement stmt=conn.prepareStatement("INSERT INTO student(student_name,student_id,class) VALUES(?,?,?)");
            stmt.setString(1, "abc");
            stmt.setString(2, "4");
            stmt.setString(3, "ukg");
            stmt.executeUpdate();
            System.out.println("query executed");
        }
        catch (ClassNotFoundException e) {
        e.printStackTrace();
      } catch (SQLException e) {
        e.printStackTrace();
        }

Please change the driverclass and connectionString

answered Jun 23, 2014 at 18:25

SparkOn

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3 Comments

Nika Tsogiaidze Over a year ago

Why mysql?I try to connect to jdbc.

Nika Tsogiaidze Over a year ago

M.Sharma throws exception from this line Class.forName("org.apache.derby.jdbc.ClientDriver");

SparkOn Over a year ago

Hi told you to change the driverclass and connection-string and please have the required jars in classpath. jar you can get here

Mohammed Ashraf · Accepted Answer · 2022-02-26 19:12:00Z

0

in my case I used PostgreSQL with maven add in pom.xml the following code

<dependency>
        <groupId>org.postgresql</groupId>
        <artifactId>postgresql</artifactId>
        <version>42.3.2</version>
</dependency>

in servlet class

Class.forName("org.postgresql.Driver").newInstance();
        Connection con = DriverManager.getConnection("jdbc:postgresql://localhost:5432/" + DB_NAME, USER, PASS);

answered Feb 26, 2022 at 19:12

Mohammed Ashraf

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