[英]Jsf2 primefaces menubar from database
我是Java新手。 我正在從數據庫表生成一個菜單欄,我能夠生成三個級別的子菜單,但我想知道如果有一天我們決定添加一個級別怎么辦。我知道菜單生成的邏輯很糟糕,但是我找不到在素數上生成子代的邏輯。 這是我查詢的sql結果。有人可以幫助獲得解決方案嗎? 還是創建一個循環而不是重復兩個查詢的想法? 任何教程或任何源代碼示例都將不勝感激。
這是我生成3級菜單的源代碼
connexion c1 = new connexion();
Connection con = c1.getConnected();
PreparedStatement ps = con
.prepareStatement("SELECT * FROM menu_options where parent_option_id is null");
// get first level menu options from database
ResultSet result = ps.executeQuery();
while (result.next()) {
DefaultSubMenu firstSubmenu = new DefaultSubMenu(
result.getString("name"));
PreparedStatement ps2 = con
.prepareStatement("SELECT * FROM menu_options where parent_option_id="
+ result.getInt("id"));
// get menu second level options from database
ResultSet result2 = ps2.executeQuery();
DefaultMenuItem item = null;
while (result2.next()) {
PreparedStatement ps3 = con
.prepareStatement("SELECT * FROM menu_options where parent_option_id="
+ result2.getInt("id"));
// get menu third level options from database
ResultSet result3 = ps3.executeQuery();
int rowcount = 0;
if (result3.last()) {
rowcount = result3.getRow();
result3.beforeFirst();
}
if (rowcount == 0) {
item = new DefaultMenuItem(result2.getString("name"));
item.setUrl(result2.getString("url"));
item.setIcon("ui-icon-arrowreturnthick-1-e");
// item.setId("fils");
firstSubmenu.addElement(item);
} else {
DefaultSubMenu firstSubmenu2 = null;
firstSubmenu2 = new DefaultSubMenu(result2.getString("name"));
while (result3.next()) {
item = new DefaultMenuItem(result3.getString("name"));
item.setUrl(result3.getString("url"));
item.setIcon("ui-icon-arrowreturnthick-1-e");
// item.setId("fils");
firstSubmenu2.addElement(item);
}
firstSubmenu.addElement(firstSubmenu2);
}
}
menu.addElement(firstSubmenu);
}
一個可能的解決方案可能是實現這些方法:
// Returns the item with no parent
private List<Item> searchParentlessItems();
// Returns the item with the given item as parent
private List<Item> searchItemChildren(Item item);
// Returns the children count
private Long countItemChildren(Item item);
// Build a SubMenu for the specified item
private SubMenu createSubMenu(Item item);
// Build a MenuItem for the specified item
private MenuItem createMenuItem(Item item);
然后一代可能看起來像
private MenuModel createMenuModel() {
MenuModel model = new DefaultMenuModel();
List<Item> rootItems = searchParentlessItems();
for (Item item : rootItems) {
boolean hasChildren = countItemChildren(item) > 0;
if (hasChildren) {
SubMenu subMenu = createSubMenu(item);
model.addElement(subMenu);
appendChildren(subMenu, item);
} else {
MenuItem menuItem = createMenuItem(item);
model.addElement(menuItem);
}
}
}
private void appendChildren(MenuGroup parentMenuItem, Item parentItem) {
List<Item> children = searchItemChildren(parentItem);
for (Item child : children) {
boolean hasChildren = countItemChildren(child) > 0;
if (hasChildren) {
SubMenu subMenu = createSubMenu(child);
parentMenuItem.addElement(subMenu);
appendChildren(subMenu, child);
} else {
MenuItem menuItem = createMenuItem(child);
parentMenuItem.addElement(menuItem);
}
}
}
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