无法组基于某些条件的一些值

Question

我有一些值从数据库返回的结果集类似下面

**resource_name   menu_name  menu_group_name** 
DepartmentAction  Department  Admin Operation 
PositionAction   Position  Admin Operation 
FoodHabitAction   FoodHabits  Admin Operation 
ReligiousAction   Religious  Admin Operation 
NationalitiesAction  Nationlities Admin Operation 

我想组RESOURCE_NAME和MENU_NAME基于menu_group_name像下面

一些事情

如果menu_group_name与所有相应的 resource_name和menu_mane相对于menu_group_name相同。

这是我试过的方法，

public Map<String,List> getMenuForLoggedinRole(int roleid){ 
     Map<String,List> menuListMap = new LinkedHashMap<String,List>(); 
     List<MenuListViewModel> menuNamesList = new ArrayList<MenuListViewModel>(); 
     MenuListViewModel menuViewModel; 
     Connection connection = getConnection(); 
     PreparedStatement ps = null; 
     ResultSet rs = null; 
     if (connection != null) { 
      try { 
       ps = connection.prepareStatement(" select ar.resource_name,ar.menu_name,mg.menu_group_name " 
         + " from m_application_resources as ar," 
         + " m_menu_groups as mg,m_access_matrix as amatrix " 
         + " where ar.resourceid = amatrix.resourceid and amatrix.roleid=?"); 
       ps.setInt(1, roleid); 
       rs = ps.executeQuery(); 
       if(rs.next()) { 
        String menu_group_name = rs.getString("menu_group_name"); 
        String resource_name = rs.getString("resource_name"); 
        String menu_name = rs.getString("menu_name"); 
        if(menuListMap.containsKey(menu_group_name)){ 
         menuNamesList =(List) menuListMap.get(menu_group_name); 
         menuViewModel = new MenuListViewModel(); 
         menuViewModel.setResource_name(resource_name); 
         menuViewModel.setMenu_name(menu_name); 
         menuNamesList.add(menuViewModel); 
         menuListMap.put(menu_group_name, menuNamesList); 
        }else{ 
         menuViewModel = new MenuListViewModel(); 
         menuViewModel.setResource_name(resource_name); 
         menuViewModel.setMenu_name(menu_name); 
         menuNamesList.add(menuViewModel); 
         menuListMap.put(menu_group_name, menuNamesList); 
        } 
       } 
      } catch (Exception ex) { 
       ex.printStackTrace(); 
      }finally { 
       try { 
        closeConnection(connection, rs, ps); 
       } catch (Exception ex) { 
        ex.printStackTrace(); 
        //use logger here 
       } 
      } 
     } 

     printMap(menuListMap); 
     return menuListMap; 
    } 

但它不给我disired输出。

我的视图模型：

public class MenuListViewModel { 

    private String resource_name = ""; 
    private String menu_name = ""; 

    public String getResource_name() { 
     return resource_name; 
    } 

    public void setResource_name(String resource_name) { 
     this.resource_name = resource_name; 
    } 

    public String getMenu_name() { 
     return menu_name; 
    } 

    public void setMenu_name(String menu_name) { 
     this.menu_name = menu_name; 
    } 

} 

和

public static void printMap(Map mp) { 
     List menuList = new ArrayList(); 
     MenuListViewModel model; 
     Iterator it = mp.entrySet().iterator(); 
     while (it.hasNext()) { 
      Map.Entry pairs = (Map.Entry)it.next(); 
      menuList =(List) pairs.getValue(); 
      for(int i=0;i<=menuList.size();i++){ 
       model =(MenuListViewModel) menuList.get(i); 
       System.out.println("Resource_name : "+model.getResource_name()); 
       System.out.println("Menu_name : "+model.getMenu_name()); 
      } 
      System.out.println(pairs.getKey() + " = " + pairs.getValue()); 
      it.remove(); // avoids a ConcurrentModificationException 
     } 
} 

请帮助。

Answer 1

如果键不包含在映射中，那么你实例化新的List。否则，如果存在，它将使用先前的列表对象。

    if(menuListMap.containsKey(menu_group_name)){ 
         menuNamesList =(List) menuListMap.get(menu_group_name); 
         menuViewModel = new MenuListViewModel(); 
         menuViewModel.setResource_name(resource_name); 
         menuViewModel.setMenu_name(menu_name); 
         menuNamesList.add(menuViewModel); 
         menuListMap.put(menu_group_name, menuNamesList); 
        }else{ 
         menuNamesList = new ArrayList<MenuListViewModel>(); 
         menuViewModel = new MenuListViewModel(); 
         menuViewModel.setResource_name(resource_name); 
         menuViewModel.setMenu_name(menu_name); 
         menuNamesList.add(menuViewModel); 
         menuListMap.put(menu_group_name, menuNamesList); 
        }