connecting to mysql with java

Question

i have written my first program but in output i cant see any thing. i create my table in mysql.

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


public class tester {

    public tester() {
    }
   public static void main(String[] args)  {


    String driver = "com.mysql.jdbc.Driver"; 
    String user = "root"; 
    String pass = "123456"; 

    Connection connection = null; 
    Statement statement = null; 
    ResultSet resultSet = null; 
ResultSet rs;
    try { 
     Class.forName(driver).newInstance(); 
     connection = DriverManager.getConnection( 
        "jdbc:mysql://./test", user, pass); 
     statement = connection.createStatement(); 
     resultSet = statement.executeQuery("SELECT * FROM  student"); 
     rs = statement.getResultSet();
        while (rs.next()) {            
           System.out.print(rs.getString("sname")+("\t")) ;
           System.out.print(rs.getString("sfamily")+("\t")) ;
           System.out.print(rs.getString("saddress")+("\t")) ;
        }
     rs.close();
     statement.close();
     connection.close();

    } catch (Exception e) { 
}
   }
}

in my output i have: run: BUILD SUCCESSFUL (total time: 0 seconds) i cant see my records. what shall i do? i add mysql-connector-java-5.1.18 in my project.

why you're using two resultset object you can use only one resultset object to retrieving the data from the database, try with the rs = statement.executeQuery() and put next line in comment i.e. rs=statement.getResultSet(); — Pratik
– Pratik, Commented Feb 1, 2012 at 6:05
Please check if the connection has been established, if it has, i think GPS provides the correct answer. And, as naresh suggested, you shouldn't swallow the exception, just print the exception message. — Alanmars
– Alanmars, Commented Feb 1, 2012 at 6:18

Dawood · Accepted Answer · 2012-02-01 06:26:07Z

1

First of all, you're not getting any exceptions because you're not printing them. Change this part:

} catch (Exception e) { 
}

to this:

} catch (Exception e) { 
    e.printStackTrace();
}

I suspect the problem would be with the connection string here:

connection = DriverManager.getConnection("jdbc:mysql://./test", user, pass);

answered Feb 1, 2012 at 6:26

Dawood

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Comments

naresh · Accepted Answer · 2012-02-01 06:08:23Z

0

Are you using some IDE like eclipse? Else, compile and run the program as following:

javac tester.java
java tester

And in your catch clause do the following, instead of completely ignoring the exception:

catch (Exception e){
e.printStackTrace();
}

answered Feb 1, 2012 at 6:08

naresh

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2 Comments

samira Over a year ago

i am using netbean. please help me. it is my first program in java. i am trying to learn.

naresh Over a year ago

go through docs.oracle.com/javase/tutorial/getStarted/cupojava/… to know how to build and run programs with netbeans IDE

A N M Bazlur Rahman · Accepted Answer · 2012-02-01 06:23:31Z

0

hey I think this code works.

public static void main(String[] args) {

    String driver = "com.mysql.jdbc.Driver";
    String user = "root";
    String pass = "";

    Connection connection = null;
    Statement statement = null;
    ResultSet rs = null;

    try {
        Class.forName(driver).newInstance();
        connection = DriverManager.getConnection(
                "jdbc:mysql://localhost/ums1", user, pass);
        statement = connection.createStatement();
        rs = statement.executeQuery("SELECT * FROM user");

        while (rs.next()) {
            System.out.print(rs.getString(1) + ("\t"));
            System.out.print(rs.getString(2) + ("\t"));
            System.out.print(rs.getString(3) + ("\t"));
        }

    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        try {
            connection.close();
            rs.close();
            statement.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

mind to change database url and table name. I tested with my one.

answered Feb 1, 2012 at 6:23

A N M Bazlur Rahman

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5 Comments

samira Over a year ago

i didnot work. how can i be sure my program connect to mysql?

samira Over a year ago

i add mysql-connector-java-5.1.18 to my project.

A N M Bazlur Rahman Over a year ago

did you add the connector in your buildpath?

samira Over a year ago

no, where is buildpath? i just add to library--- add jar files

A N M Bazlur Rahman Over a year ago

are you using eclipse ? look this image : dl.dropbox.com/u/44236198/buildpath.PNG

gprathour · Accepted Answer · 2012-02-01 06:27:40Z

0

Try with the following code

 Class.forName("com.mysql.jdbc.Driver");
 connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/test",user,pass);
 statement = connection.createStatement();
 resultSet = statement.executeQuery("SELECT * FROM  student");
 while (resultSet.next()) {
        System.out.print(resultSet.getString("sname")+("\t")) ;
        System.out.print(resultSet.getString("sfamily")+("\t")) ;
        System.out.print(resultSet.getString("saddress")+("\t")) ;
 }

And ADD THIS to catch block

catch (Exception e) { 
      e.printStackTrace();
}

That's why you are not getting any exception.

Suggestions

You don't need two different result sets. You can do this way too :

resultSet = statement.executeQuery("SELECT * FROM  student");
while (resultSet.next()) {
   System.out.print(resultSet.getString("sname")+("\t")) ;
   System.out.print(resultSet.getString("sfamily")+("\t")) ;
   System.out.print(resultSet.getString("saddress")+("\t")) ;
}

Close the connection, result set etc. in finally block.
Your class name should be Tester according to Java Naming Conventions.

edited Feb 1, 2012 at 6:27

answered Feb 1, 2012 at 6:07

gprathour

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2 Comments

gprathour Over a year ago

@sami are you using IDE or running program from console ? are you getting any exception while running it ?

gprathour Over a year ago

@sami try to replace your code with the code I wrote in answer.

Suresh · Accepted Answer · 2012-02-01 06:34:38Z

0

1.You dont need two resultset.You can go below code.

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

//</editor-fold>
/**
 *
 * @author mohsen
 */
public class tester {

    public tester() {
    }
   public static void main(String[] args)  {


    String driver = "com.mysql.jdbc.Driver"; 
    String user = "root"; 
    String pass = "123456"; 
    String dbUrl ="jdbc:mysql://localhost:3306/test1";

    Connection connection = null; 
    Statement statement = null; 
   /* ResultSet resultSet = null; */
ResultSet rs =null;
    try { 
     Class.forName(driver).newInstance(); 
     connection = DriverManager.getConnection(dbUrl, user, pass); 
     statement = connection.createStatement(); 
     rs = statement.executeQuery("SELECT * FROM  student"); 
   //  rs = statement.getResultSet();
        while (rs.next()) {            
           System.out.print(rs.getString("sname")+("\t")) ;
           System.out.print(rs.getString("sfamily")+("\t")) ;
           System.out.print(rs.getString("saddress")+("\t")) ;
        }
     rs.close();
     statement.close();
     connection.close();

    } catch (Exception e) { 

}
   }

}

2.Try to print Exception.So you got what is error in that.

3.Always close connection in finally.

edited Feb 1, 2012 at 6:34

answered Feb 1, 2012 at 6:23

Suresh

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1 Comment

Suresh Over a year ago

It works dude i already tested and after i put it.You have to add one jar mysql.

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