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POretrieving value from database in java
 

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    <blockquote> <p><strong>Possible Duplicate:</strong><br> <a href="https://stackoverflow.com/questions/12762835/retrieving-values-from-database-in-java">retrieving values from database in java</a> </p> </blockquote> <p>I am making AGAIN another program that retrieves the inputted data/values of fields from the database I created. but this time, my inputted value will be coming from the JtextField I created. I wonder what's wrong in here bec when I'm running it the output is always null. </p> <p>in this program i will convert the inputted value of my JTextField into int. here it is:</p> <pre><code>public class ButtonHandler implements ActionListener { public void actionPerformed(ActionEvent e) { if(e.getSource() == extendB) { ExtensionForm extend = new ExtensionForm(); extend.setVisible(true); } else if(e.getSource()== searchB) { //get text from the textField String guest = guestIDTF.getText(); //parse the string to integer for retrieving of data int id = Integer.parseInt(guest); GuestsInfo guestInfo = new GuestsInfo(id); Room roomInfo = new Room(id); String labels[] = {guestInfo.getFirstName()+" "+guestInfo.getLastName(),""+roomInfo.getRoomNo(),roomInfo.getRoomType(),guestInfo.getTime(),"11:00"}; for(int z = 0; z&lt;labels.length; z++) { labelDisplay[z].setText(labels[z]); } </code></pre> <p>in my second class it retrieves the inputted values of fields from the database I created here's the code: import java.sql.*;</p> <p>public class Room {</p> <pre><code>private String roomType; private int guestID, roomNo; private Connection con; private PreparedStatement statement; public Room(){ try { Class.forName("com.mysql.jdbc.Driver"); con = DriverManager.getConnection( "jdbc:mysql://localhost:3306/3moronsdb","root",""); } catch (Exception e) { e.printStackTrace(); } } public Room(int guestsID) { this(); try{ statement = con.prepareStatement("SELECT * FROM guest WHERE guestID=?"); statement.setInt(1, guestID); ResultSet rs = statement.executeQuery(); while(rs.next()){ this.guestID = rs.getInt(1); this.roomType = rs.getString(2); this.roomNo = rs.getInt(3); } }catch(Exception e){ System.out.print(e); } } //Constructor for setting rate public Room(String roomType, int roomNo) { this(); try { statement = con.prepareStatement("Insert into room(roomType, roomNo) values(?,?)"); statement.setString(1, roomType); statement.setInt(2, roomNo); statement.executeUpdate(); } catch(Exception e) { e.printStackTrace(); return; } } //getting roomType public String getRoomType(){ return roomType; } //getting roomNo public int getRoomNo(){ return roomNo; } //getting guestID public int getGuestId(){ return guestID; } </code></pre> <p>}</p> <p>i already insert some values in my 3moronsdb which are ( 1, Classic , 103). here's my TEST main class:</p> <pre><code>public class TestMain { public static void main(String [] a){ GuestsInfo guest = new GuestsInfo(1); //note that this instantiation is the other class which i just ask the other day.. (https://stackoverflow.com/questions/12762835/retrieving-values-from-database-in-java) Room rum = new Room(1); System.out.print(rum.getRoomType()+" "+ guest.getFirstName()); } } </code></pre> <p>when i'm running it it only gives me null output for the Room class but i am getting the output of the GuestsInfo class which is 'Ericka'. Can you help me guys? I know I ask this kind of problem yesterday but i really don't know what's wrong in here now.. </p>
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    1. COI'm curious about `SELECT * FROM guest WHERE guestID=?` from the `Room` class, shouldn't this be selecting from the room table? You would have picked this up if you had used the column name when retrieving the values from the result set instead of using the column index. It is possible the column indices may change (the same can be said for the name) as the order is based on how the database decides it should return the result.
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    2. CO@MadProgrammer can you give me an example on what you're saying? actually, i use the select statement to retrieve the data from the database. pls. correct me.
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    3. COWhat @MadProgrammer is saying is, if your select statement was 'SELECT fname, lname from TABLE' you should use rs.getString("fname") instead of rs.getString(1) because if you change the query to 'SELECT lname, fname ...' rs.getString(1) your would be no longer be retrieving fname but rs.getString("fname") would.
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