Load objects from DataBase into an ArrayList, then into a jComboBox in a GUI

[jeata]

Hello

I'm having a small problem adding objects that I fetched from my database to an arraylist. I'm using 3 classes(different pacakges). A class called "BranchMapper.java"(the mapper from the db obviously), "Branch.java" (The object class) and "BranchGUI"(where the jComboBox resides). I've did this so far. I need the objects to be added to an ArrayList in the mapper class, so I can fetch the arraylist and append it to the jComboBox in the visual class

BranchMapper class

public Branch getAllBranches(Connection con) 
    {
		Branch br = null;
		String SQLString1 =       // get branch
            "select * from branch";
       PreparedStatement statement=null;
        try
        {
            //=== get branch
            statement = con.prepareStatement(SQLString1);
            ResultSet rs  = statement.executeQuery();
            if(rs.next())
            {
            	
                  br = new Branch(rs.getInt(1), 
                                  rs.getString(2));
            }                     
        }
        catch (Exception exc)
        {   
            System.out.println("Fail in BranchMapper - getAllBranches");
            System.out.println(exc.getMessage());
        }
        
        return br;                         
    }
	
	
     public ArrayList<Branch> branchArray(){
		return null;
    	 
     }

"Branch" Class

int branchid;
	  String branchname;
	  
	  public Branch(int bi, String bn)
	  {
	    branchid=bi;
	    branchname=bn;
	       
	  }

	  //======AUTOGENERATED GETTERS AND SETTERS======//
	  
	   public int getBranchid() {
			return branchid;
		}

		public void setBranchid(int branchid) {
			this.branchid = branchid;
		}

		public String getBranchname() {
			return branchname;
		}

		public void setBranchname(String branchname) {
			this.branchname = branchname;
		}

"GUI" Class

private JComboBox getJComboBox() {
		if (jComboBox == null) {
			jComboBox = new JComboBox();
			jComboBox.setBounds(new Rectangle(3, 80, 280, 24));
			try{
				BranchMapper bm = new BranchMapper();
				Branch br = bm.getAllBranches(getConnection());
				String brn = br.getBranchname();
				String[] numStrings = {brn};

	             for(int i=0; i<numStrings.length; i++)
	               {
		              jComboBox.addItem(new String(numStrings[i]));
	               }
			  }catch (Exception exasd)
			  {
				  System.out.println(exasd);
			  }
			  
			  //Directly load into comboBox
			  
			  
		}
		return jComboBox;
	}

[Tolls]

public Branch getAllBranches(Connection con)

Presumably that should be returning a List<Branch> then?

[jeata]

Yes, thats right. The main question is still the same: How do I make it iterate through the objects, adding them to the arraylist or list ??

public Branch getAllBranches(Connection con)

Presumably that should be returning a List<Branch> then?

[Tolls]

You're already iterating over the result set, so just add each new Branch to a List.
I really don't see what problem you're having because you have just described exactly what you need to do, and you even have code that almost does it.

Return a List<Branch> object instead of the Branch you are currently returning and go from there.

[jeata]

see I already did that and it doesn't return anything

[Tolls]

So why didn't you show that code?
Then we could explain why that code (which is nearer to what you need) is going wrong.

[jeata]

Showing Code now

Mapper Class

public ArrayList<Branch> getAllBranches(Connection con) 
    {
		ArrayList l1 = null;
		Branch br = null;
		String SQLString1 =       // get branch
            "select * from branch";
       PreparedStatement statement=null;
        try
        {
            //=== get branch
            statement = con.prepareStatement(SQLString1);
            ResultSet rs  = statement.executeQuery();
            while(rs.next())
            {
            	 l1.add(br = new Branch(rs.getInt(1), rs.getString(2)));
                  
            }                     
        }
        catch (Exception exc)
        {   
            System.out.println("Fail in BranchMapper - getAllBranches");
            System.out.println(exc.getMessage());
        }
        
        return l1;

GUI Class

private JComboBox getJComboBox() {
		if (jComboBox == null) {
			jComboBox = new JComboBox();
			jComboBox.setBounds(new Rectangle(3, 80, 280, 24));
			try{
				BranchMapper bm = new BranchMapper();
	            ArrayList br = bm.getAllBranches(getConnection());
		        jComboBox.addItem(br);
	         
			  }catch (Exception exasd)
			  {
				  System.out.println(exasd);
			  }
			  
			  //Directly load into comboBox
			  
			  
		}
		return jComboBox;

[JosAH]

Showing Code now

Mapper Class

public ArrayList<Branch> getAllBranches(Connection con) 
    {
		ArrayList l1 = null;
		Branch br = null;
		String SQLString1 =       // get branch
            "select * from branch";
       PreparedStatement statement=null;
        try
        {
            //=== get branch
            statement = con.prepareStatement(SQLString1);
            ResultSet rs  = statement.executeQuery();
            while(rs.next())
            {
            	 l1.add(br = new Branch(rs.getInt(1), rs.getString(2)));
                  
            }

Your ArrayList<Branch> l1 is null (see your own code) and you never gave it a non-null value before you're trying to add values to it (also see your own code). That is a nono.

kind regards,

Jos

[Tolls]

Also (though not the problem:

            	 l1.add(br = new Branch(rs.getInt(1), rs.getString(2)));

should be:

            	 l1.add(new Branch(rs.getInt(1), rs.getString(2)));

as the assignment to br is completely redundant.

[jeata]

Doesn't help, I gave the ArrayList an instantiation, but still doesn't solve the problem, gives only one result, not an ArrayList of results

ArrayList<Branch> l1 = new ArrayList<Branch>();

Your ArrayList<Branch> l1 is null (see your own code) and you never gave it a non-null value before you're trying to add values to it (also see your own code). That is a nono.

kind regards,

Jos

[jeata]

Solved the problem, thank you people

Mapper Class

public ArrayList<Branch> getAllBranches(Connection con) 
    {
		ArrayList<Branch> l1 = new ArrayList<Branch>();
		String SQLString1 =       // get branch
            "select * from branch";
       PreparedStatement statement=null;
        try
        {
            //=== get branch
            statement = con.prepareStatement(SQLString1);
            ResultSet rs  = statement.executeQuery();
            while(rs.next())
            { 
                l1.add(new Branch(rs.getInt(1), rs.getString(2)));
            }                     
        }
        catch (Exception exc)
        {   
            System.out.println("Fail in BranchMapper - getAllBranches");
            System.out.println(exc);
        }
        
        return l1;                         
    }

GUI Class

	private JComboBox getJComboBox() {
		if (jComboBox == null) {
			jComboBox = new JComboBox();
			jComboBox.setBounds(new Rectangle(3, 80, 280, 24));
			try{
				BranchMapper bm = new BranchMapper();
	            ArrayList<Branch> br = bm.getAllBranches(getConnection());
	            Iterator<Branch> itr = br.iterator();
	            while (itr.hasNext()) 
	            {
	              Branch branch = itr.next();
	              jComboBox.addItem(branch.getBranchname());
	              System.out.print("BranchName is");
	            }
	         
			  }catch (Exception exasd)
			  {
				  System.out.println(exasd);
			  }
			  
			  //Directly load into comboBox
			  
			  
		}
		return jComboBox;
	}

[Tolls]

		        jComboBox.addItem(br);

To quote the API:
"Adds an item to the item list."

Which in your case seems to be the array list, which will display the toString of that List.