Java JTable Displaying database records

Question

I have problems fetching the database records, what is the best way to get the database records display in the JTable, so right now I used the resultset for fetching records and store it in the Object[][] array, I wanted this variable lets say Object[][] data its value to be displayed on JTable, I donn't know if I'm doing this right. And how can I initialize my Object[][] data size depending on the records inside my database. thanks

Here are my code:

ResultSet rs = null;
Statement sql = null;
Object[][] data = new Object[100][100];

        String query = "SELECT * FROM INVENTORY";
        sql = con.createStatement();
        sql.executeQuery(query);
        rs = sql.getResultSet();

        while(rs.next()){
            for(int i = 0; i < data.length; i++){
                for(int j = 0; j < data[i].length; j++){
                    int valId = rs.getInt(1);
                    String valName = rs.getString(2);
                    String valCat = rs.getString(3);
                    String valDesc = rs.getString(4);
                    double  valPrice = rs.getDouble(5);
                    int valstock = rs.getInt(6);
                    int valSupply = rs.getInt(7);

                    System.out.println(valId);
                    System.out.println(valName);
                    System.out.println(valCat);
                    System.out.println(valDesc);
                    System.out.println(valPrice);
                    System.out.println(valstock);
                    System.out.println(valSupply);

well as you can see I use multiple for loops for fetching the records, Is it right to use multiple for loops? or is there any easy way and how can I initialize my Object[][] array depending to the total records on my database?

Haven't you asked this question before?? stackoverflow.com/questions/12242333/… — MadProgrammer
– MadProgrammer, Commented Sep 4, 2012 at 6:01
Yep but it only display on the console how can I display it in the JTable I called the variable data but nothing show not but column header only. can you help me with this? — Zyrax
– Zyrax, Commented Sep 4, 2012 at 6:02
The concept of the previous question is exactly the same. It produces an Object[][] array, which can then be fed directly to a table model. — MadProgrammer
– MadProgrammer, Commented Sep 4, 2012 at 6:26

norbitheeviljester · Accepted Answer · 2012-09-04 06:09:30Z

2

you should use an ArrayList

First you create the data holder:

ArrayList<Object[]> data = new ArrayList<Object[]>();

Then you iterate over the resultSet row by row and create a new Object[] array each time you want to save the row. The number of items in the table should be the number of columns in your row:

while(rs.next()){
    Object[] row = new Object[]{rs.getInt(1), 
                    rs.getString(2), 
                    rs.getString(3), 
                    rs.getString(4),
                    rs.getDouble(5),
                    rs.getInt(6),
                    rs.getInt(7)};
    data.add(row);
}
Object[][] realData = data.toArray(new Object[data.size()][]);

It would also be great if you changed the SQL query to not use the '*' and just list the fields.

answered Sep 4, 2012 at 6:09

norbitheeviljester

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3 Comments

Zyrax Over a year ago

Men both of your answer is so good, It works! now it is displayed on my JTable Thanks.. What is the disadvantage of using * in sql statement? sorry I'm noob in Java.

MadProgrammer Over a year ago

1. Order of columns. You're currently assuming the order is know, you shouldn't do that. At worse case, you should be using column names to retrieve the values from the result set. 2. You could be pulling more data base from the database then you need. What if the table had 100's of columns, you'd be wasting time (processing on the DB) and bandwidth on the retrival

Zyrax Over a year ago

Thanks, your right and it will slow down the performance of my system.

MadProgrammer · Accepted Answer · 2012-09-04 06:17:30Z

2

As I started in my previous answer.

You probably won't know how many rows are coming from the database in advance. There are techniques you can use, but they are only guesses at best (mind you, it's been a while since I played with JDBC).

Without knowing upfront the number of rows, you need some kind dynamic array. Funny enough, Java provides one. It's called ArrayList. This allows you to add elements to it without knowing how many elements you actually need.

Secondly, I'd store you row results in an Object that best represents that object, this will greatly reduce the complexity of the data structure and make it easier to adopt changes into the code, cause how long will column x be the value you're expecting...

Something like

public class Inventory {

    private int id;
    private String name;
    private String catagory;
    private String description;
    private double  price;
    private int stock;
    private int supply;

    public Inventory(int id, String name, String catagory, String description, double price, int stock, int supply) {
        this.id = id;
        this.name = name;
        this.catagory = catagory;
        this.description = description;
        this.price = price;
        this.stock = stock;
        this.supply = supply;
    }

    public void setCatagory(String catagory) {
        this.catagory = catagory;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public void setId(int id) {
        this.id = id;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    public void setStock(int stock) {
        this.stock = stock;
    }

    public void setSupply(int supply) {
        this.supply = supply;
    }

    public String getCatagory() {
        return catagory;
    }

    public String getDescription() {
        return description;
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public double getPrice() {
        return price;
    }

    public int getStock() {
        return stock;
    }

    public int getSupply() {
        return supply;
    }

}

For example.

The I'd store this information into a List

List<Inventory> inventoryList = new ArrayList<Inventory>(50); // This is a "seed" value to helps performance
while(rs.next()){
    Inventory inventory = new Inventory(rs.getInt(1),
        rs.getString(2),
        rs.getString(3),
        rs.getString(4),
        rs.getDouble(5),
        rs.getInt(6),
        rs.getInt(7))
    inventoryList.add(inventory);
}

Basically from there, I'd be tempted to simply use the list. This means you will probably need to implement our own AbstractTableModel, but it will be far more useful to you in the long run

answered Sep 4, 2012 at 6:17

MadProgrammer

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3 Comments

Zyrax Over a year ago

what for is the 50 in the ArrayList is that the total number of result to be displayed?

MadProgrammer Over a year ago

From the JavaDocs

Each ArrayList instance has a capacity. The capacity is the size of the array used to store the elements in the list. It is always at least as large as the list size. As elements are added to an ArrayList, its capacity grows automatically. The details of the growth policy are not specified beyond the fact that adding an element has constant amortized time cost.

MadProgrammer Over a year ago

To answer your question simply, the "50" is a seed, a guess. It's there to make the array list faster when adding new elements over time. The ArrayList is dynamic, meaning that it doesn't have a fixed capacity, it will grow as you add more elements to it, meaning you don't need to know the number of elements you will need upfront

David B · Accepted Answer · 2012-09-04 06:10:50Z

1

Make sure you initialize the size of data with the approriate row and column counts. To get the row count you may follow the procedure set here. And to get the column count, the answer is found on the JavaDocs.

In this way you remove one of the loops you have above. Leaving you only with

final int columnCount = rs.getMetaData().getColumnCount();
int row = 0;
while(rs.next()) {
   for(int index = 0; index < columnCount; index ++) {
      data[row][index] = rs.getObject(index);
   }
   row ++;
}

Or instead of using Object[][], use List<Model> wherein the Model follows the MVC architecture.

answered Sep 4, 2012 at 6:10

David B

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1 Comment

MadProgrammer Over a year ago

I'd be wary about suggesting the use of ResultSet.last without knowing if the database and driver supports bi-directional cursors - doesn't mean I don't like the suggestion though ;)

Kumar Vivek Mitra · Accepted Answer · 2012-09-04 06:18:22Z

1

Using Vectors from java.util.collection will solve your problem.....

See this nice example :

http://chang.advits.com/populate-data-from-database-into-jtable-in-netbeans

answered Sep 4, 2012 at 6:18

Kumar Vivek Mitra

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1 Comment

mKorbel Over a year ago

or Table From Database by @camickr +1

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