[英]Jsf2 primefaces menubar from database
我是Java新手。 我正在从数据库表生成一个菜单栏,我能够生成三个级别的子菜单,但我想知道如果有一天我们决定添加一个级别怎么办。我知道菜单生成的逻辑很糟糕,但是我找不到在素数上生成子代的逻辑。 这是我查询的sql结果。有人可以帮助获得解决方案吗? 还是创建一个循环而不是重复两个查询的想法? 任何教程或任何源代码示例都将不胜感激。
这是我生成3级菜单的源代码
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);
}
一个可能的解决方案可能是实现这些方法:
// 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);
然后一代可能看起来像
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);
}
}
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.