miércoles, 22 agosto 2007

java.lang.OutOfMemoryError: PermGen space // More memory for Tomcat under windows

In many cases, web applications give OutOfMemoryError when their threads require high levels of  memory. Image manipulation or intensive database use or calculation can lead to this very common problem.

Normally when you get an OutOfMemory error in a desktop application, you can solve this problem by specifying the java commands -Xms*** (initial Java heap size) and -Xmx*** (maximum Java heap size) when running your program.

To solve this issue in tomcat, you must specify these options in the tomcat startup command / script / batch. In windows tomcat is installed as a service. Tomcat provides a configuration tool to set up these and other parameters. you can find it in (Start->Programs->Apache Tomcat->Configure Tomcat) or by running (.\bin\tomcat5w.exe" //EN//Tomcat5).

Tomcat Properties

Under the "Java" tab you can find two options:

  • Initial memory pool: This corresponds to -Xms, you can specify the size in Mb.
  • Maximum memory pool: This corresponds to -Xmx, you can specify the size in Mb.

Now you can specify a higher maximum memory so that Tomcat doesn't get the OutOfMemoryError. Remember to take in consideration your hardware capabilities.

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Posted by admin at 3:55 PM in Apache Tomcat

viernes, 3 agosto 2007

Updated: Displaying a jTable inside another jTable // JTable cellRenderer

After some users asking for answers in my past post, I updated the code of the embedded JTable to make it less buggy and more stable.

This is the "new" code:

/* We initialize the Objects where we'll store our data */
/* First an array Object which will be our main table */
Object[][] data = null;
/* We create an Array String to hold the name of the main table columns In this example case we are going to store a contact name, his email address(es) and his phone numer(s) We're also going to store the creation date.*/
String[] columns = {"Name", "E-Mail","Phone","Creation Date"};
/* First thing is  to populate our data object with some example values*/
    public void populateData(){
        /* Two contacts*/
        data = new Object[3][columns.length];
        data[0][0] = "Peter";
        String[] emails = {"peter@yahoo.com", "strange@name.com"};
        data[0][1] = emails;
        String[] phones = {"555 35 25 65" , "555 35 24 63"};
        data[0][2] = phones;
        data[0][3] = new Date();
        data[1][0] = "Jackson";
        data[1][1] = "Jack@hotmail.com";
        String[] phones2 = {"555 35 24 33" , "555 11 88 88", "332 55 25 34"};
        data[1][2] = phones2;
        data[1][3] = new Date();
        data[2][0] = "Robert";
        data[2][1] = "rob@hotmail.com";
        data[2][2] = "555 28 95 81";
        data[2][3] = new Date();
        /* AS you can see, we've stored two contacts one with two e-mail
         accounts and two phone numbers, and another member with three phone
         numbers*/
    }
    /* Next we create our table models */
    public void createModel(){
        /* First we create the main model
         We overide the AbstractTableModel necessary methods*/
        AbstractTableModel  modelo = new AbstractTableModel() {
          public String getColumnName(int col) {
                return columns[col].toString();
            }
          public Class getColumnClass(int col) {
              if(getRowCount() <1)return null;
            return data[0][col].getClass();
          }
          public int getRowCount() { return data.length; }
          public int getColumnCount() { return columns.length;}
          public Object getValueAt(int row, int col) {
                return data[row][col];
          }
          public boolean isCellEditable(int row, int col){ return true; }
          public void setValueAt(Object value, int row, int col) {
            data[row][col] =  value;
            fireTableCellUpdated(row, col);
          }};
          /* We apply the model to the main jTable */
          jTableData.setModel(modelo);
          /* We create a cell Renderer to display the data of the multivalue
           fields*/
          TableCellRenderer jTableCellRenderer = new TableCellRenderer() {
              /* Magic Happens */
              public Component getTableCellRendererComponent(JTable table,
                      Object value, boolean isSelected, boolean hasFocus,
                      int row, int column) {
                  /* If what we're displaying isn't an array of values we
                   return the normal renderer*/
                    if(!value.getClass().isArray()){
                       return table.getDefaultRenderer( 
                               value.getClass()).getTableCellRendererComponent(
                               table, value, isSelected, hasFocus,row, column);
                    }
                    else{
                        final Object[] passed = (Object[])value;             
                        /* We create the table that will hold the multivalue
                         *fields and that will be embedded in the main table */
                        JTable embedded = new JTable(
                            new AbstractTableModel() {
                                public int getColumnCount() {
                                    return 1;
                                }
                                public int getRowCount() {
                                    return passed.length;
                                }
                                public Object getValueAt(int rowIndex, int columnIndex) {
                                    return passed[rowIndex];
                                }
                                public boolean isCellEditable(int row, int col){ return true; }
                        });
                         
                        if(isSelected){
                            embedded.setBackground(jTableData.getSelectionBackground());
                            embedded.setForeground(jTableData.getSelectionForeground());
                        }
                        if(hasFocus){
                            embedded.setRowSelectionInterval(0,1);
                        }
                        /* If this is what you plan to enable mouseClick detection,
                            in your table, IT WONT WORK. Have a look at TableCellEditor.*/
                        embedded.addMouseListener(new MouseAdapter() {
                            public void mouseClicked(java.awt.event.MouseEvent evt) {
                                System.out.println("PEPE");
                            }
                        });
                        
                        setPreferredSize(embedded.getPreferredSize());
                         if(getPreferredSize().height != table.getRowHeight(row))
                            {
                                table.setRowHeight(row, getPreferredSize().height);
                            }

                        return embedded;
                    }
              }
          };
          /* Finally we apply the new cellRenderer to the whole table */
          TableColumnModel tcm = jTableData.getColumnModel();
          for(int it = 0; it < tcm.getColumnCount(); it++){
              tcm.getColumn(it).setCellRenderer(jTableCellRenderer);
             // tcm.getColumn(it).setCellEditor(jTableCellEditor);
          }
          /*Note: if we need to edit the values inside the embedded jtable
           * we will need to create a TableCellEditor too. */
          
    }

JTable with another embedded JTable

In the above image you can see the result.

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Posted by admin at 8:41 AM in Java

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