Working with multiple custom table templates that eliminate duplicate code

Like other Swing models (ex: DefaultComboBoxModel , DefaultListModel ), we can use Generics to create a flexible and reusable table that also provides an API for working with custom POJOs.

This table model will have the following special features:

• It extends from AbstractTableModel
  
  to take advantage of the event handling of the table model.
• Unlike the CustomerTableModel
  
  one shown above, this table model should be abstract because it should not override a method getValueAt()
  
  : simply because we do not know the type of class or data that this table will handle, the task of overriding the above method is left in subclasses.
• Inherits empty implementation setValueAt()
  
  from AbstractTableModel
  
  . This makes sense because it is isCellEditable()
  
  also inherited from this class and always returns false
  
  .
• The default implementation is getColumnClass()
  
  also inherited and always returns Object.class
  
  .

These functions make this table model very easy to implement depending on our requirements:

• If we need to display a read-only table, we have to override the 2 top: getValueAt()
  
  and methods getColumnClass()
  
  (this latter is recommended but not required).
• If our table should be editable, we need to override 4 top methods: the two above plus isCellEditable()
  
  and setValueAt()
  
  .

Let's take a look at our table model code:

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import javax.swing.table.AbstractTableModel;

/**
 * Abstract base class which extends from {@code AbstractTableModel} and 
 * provides an API to work with user-defined POJO as table rows. Subclasses 
 * extending from {@code DataObjectTableModel} must implement 
 * {@code getValueAt(row, column)} method. 
 * <p />
 * By default cells are not editable. If those have to be editable then 
 * subclasses must override both {@code isCellEditable(row, column)} and 
 * {@code setValueAt(row, column)} methods.
 * <p />
 * Finally, it is not mandatory but highly recommended to override 
 * {@code getColumnClass(column)} method, in order to return the appropriate 
 * column class: default implementation always returns {@code Object.class}.
 * 
 * @param <T> The class handled by this TableModel.
 * @author dic19
 */
public abstract class DataObjectTableModel<T> extends AbstractTableModel {

    private final List<String> columnNames;
    private final List<T> data;

    public DataObjectTableModel() {
        this.data = new ArrayList<>();
        this.columnNames = new ArrayList<>();
    }

    public DataObjectTableModel(List<String> columnIdentifiers) {
        this();
        if (columnIdentifiers != null) {
            this.columnNames.addAll(columnIdentifiers);
        }
    }

    @Override
    public int getRowCount() {
        return this.data.size();
    }

    @Override
    public int getColumnCount() {
        return this.columnNames.size();
    }

    @Override
    public String getColumnName(int columnIndex) {
        return this.columnNames.get(columnIndex);
    }

    public void setColumnNames(List<String> columnNames) {
        if (columnNames != null) {
            this.columnNames.clear();
            this.columnNames.addAll(columnNames);
            fireTableStructureChanged();
        }
    }

    public List<String> getColumnNames() {
        return Collections.unmodifiableList(this.columnNames);
    }

    public void addDataObject(T dataObject) {
        int rowIndex = this.data.size();
        this.data.add(dataObject);
        fireTableRowsInserted(rowIndex, rowIndex);
    }

    public void addDataObjects(List<T> dataObjects) {
        if (!dataObjects.isEmpty()) {
            int firstRow = data.size();
            this.data.addAll(dataObjects);
            int lastRow = data.size() - 1;
            fireTableRowsInserted(firstRow, lastRow);
        }
    }

    public void insertDataObject(T dataObject, int rowIndex) {
        this.data.add(rowIndex, dataObject);
        fireTableRowsInserted(rowIndex, rowIndex);
    }

    public void deleteDataObject(int rowIndex) {
        if (this.data.remove(this.data.get(rowIndex))) {
            fireTableRowsDeleted(rowIndex, rowIndex);
        }
    }

    public void notifyDataObjectUpdated(T domainObject) {
        T[] elements = (T[])data.toArray();
        for (int i = 0; i < elements.length; i++) {
            if(elements[i] == domainObject) {
                fireTableRowsUpdated(i, i);
            }
        }
    }

    public T getDataObject(int rowIndex) {
        return this.data.get(rowIndex);
    }

    public List<T> getDataObjects(int firstRow, int lastRow) {
        List<T> subList = this.data.subList(firstRow, lastRow);
        return Collections.unmodifiableList(subList);
    }

    public List<T> getDataObjects() {
        return Collections.unmodifiableList(this.data);
    }

    public void clearTableModelData() {
        if (!this.data.isEmpty()) {
            int lastRow = data.size() - 1;
            this.data.clear();
            fireTableRowsDeleted(0, lastRow);
        }
    }
}

      

        
        
        
      

    

So, taking this table model and class Customer

, the complete implementation would look like this:

String[] header = new String[] {"Entry date", "Name", "Address", "Phone number"};
DataObjectTableModel<Customer> model = new DataObjectTableModel<>(Arrays.asList(header)) {
    @Override
    public Class<?> getColumnClass(int columnIndex) {
        switch (columnIndex) {
            case 0: return Date.class;
            case 1: return String.class;
            case 2: return String.class;
            case 3: return String.class;
                default: throw new ArrayIndexOutOfBoundsException(columnIndex);
        }
    }

    @Override
    public Object getValueAt(int rowIndex, int columnIndex) {
        Customer customer = getDataObject(rowIndex);
        switch (columnIndex) {
            case 0: return customer.getEntryDate();
            case 1: return customer.getName();
            case 2: return customer.getAddress();
            case 3: return customer.getPhoneNumber();
                default: throw new ArrayIndexOutOfBoundsException(columnIndex);
        }
    }

    @Override
    public boolean isCellEditable(int rowIndex, int columnIndex) {
        return true;
    }

    @Override
    public void setValueAt(Object aValue, int rowIndex, int columnIndex) {
        if (columnIndex < 0 || columnIndex >= getColumnCount()) {
            throw new ArrayIndexOutOfBoundsException(columnIndex);
        } else {
            Customer customer = getDataObject(rowIndex);
            switch (columnIndex) {
                case 0: customer.setEntryDate((Date)aValue); break;
                case 1: customer.setName((String)aValue); break;
                case 2: customer.setAddress((String)aValue); break;
                case 3: customer.setPhoneNumber((String)aValue); break;
            }
            fireTableCellUpdated(rowIndex, columnIndex);
        }
    }
};

      

        
        
        
      

    

As we can see, in a few lines of code (LOC <50) we have a complete implementation.

Does it work with JPA objects?

This happens as long as objects have public getters and setters. Unlike the JPA implementation, this table model does not work with reflection, so we need to access the object's properties using the public interface of the class to implement the getValueAt()

and methods setValueAt()

.

Does it work with JDBC?

No no. We would have to wrap the result set in domain classes and use the suggested class interface as above.

Does it work with default Java classes?

Yes Yes. Once again using the suggested class interface. For example, let's say a class java.io.File

, we could have the following table model implementation:

String[] header = new String[] {
    "Name",
    "Full path",
    "Last modified",
    "Read",
    "Write",
    "Execute",
    "Hidden",
    "Directory"
};

DataObjectTableModel<File> model = new DataObjectTableModel<File>(Arrays.asList(header)) {
    @Override
    public Class<?> getColumnClass(int columnIndex) {
        switch (columnIndex) {
            case 0: return String.class;
            case 1: return String.class;
            case 2: return Date.class;
            case 3: return Boolean.class;
            case 4: return Boolean.class;
            case 5: return Boolean.class;
            case 6: return Boolean.class;
            case 7: return Boolean.class;
                default: throw new ArrayIndexOutOfBoundsException(columnIndex);
        }
    }

    @Override
    public Object getValueAt(int rowIndex, int columnIndex) {
        File file = getDataObject(rowIndex);
        switch (columnIndex) {
            case 0: return file.getName();
            case 1: return file.getAbsolutePath();
            case 2: return new Date(file.lastModified());
            case 3: return file.canRead();
            case 4: return file.canWrite();
            case 5: return file.canExecute();
            case 6: return file.isHidden();
            case 7: return file.isDirectory();
                default: throw new ArrayIndexOutOfBoundsException(columnIndex);
        }
    }
};